1. Three identical resistors are connected across a potential difference V so that one of them is in parallel with the other two which are connected in series. The power dissipated through the first one, compared to the power dissipated by each of the other two, is approximately

A the same

B half as much

C twice as much

D four times as much(Total 1 mark)

2. A circuit is set up as shown in the diagram.

1 0Ω

2 0Ω4 0Ω

When the switch is closed, the potential difference across the 20 Ω resistor would

A equal the potential difference across the 10 Ω resistor

B be twice the potential difference across the 10 Ω resistor

C equal the potential difference across the 40 Ω resistor

D be half the potential difference across the 40 Ω resistor(Total 1 mark)

3. How much electrical energy is required to move 4.00 mC of charge through a potential difference of 36.0 V?

A 1.11 × 10–4 J

B 0.144 J

C 144 J

D 9000 J(Total 1 mark)

4. A source of light emits a train of waves lasting 0.04 μs. The light has a wavelength of 600 nm

and the speed of light is 3 × 108 m s–1. How many complete waves are sent out?

A 2.0 × 107

B 4.5 × 107

C 2.0 × 1010

D 4.5 × 1013

(Total 1 mark)

5. Which of the following graphs gives the current-potential difference characteristic of an NTC thermistor?

I

V

I

V

I

V

I

V

A B C D(Total 1 mark)

6. Which of the following statements about standing waves is true?

A particles between adjacent nodes all have the same amplitude.

B particles undergo no disturbance at an antinode.

C particles immediately either side of a node are moving in opposite directions.

D particles between adjacent nodes are out of phase with each other.(Total 1 mark)

7. The diagram shows a wave on a rope. The wave is travelling from left to right.

L

M

At the instant shown, point L is at a maximum displacement and point M has zero displacement. Which row in the table correctly describes the motion of points L and M during the next half cycle of the wave?

Point L Point M

A rises falls

B rises falls then rises

C rises then falls rises

D rises then falls falls then rises(Total 1 mark)

8. Electromagnetic waves are produced by oscillating charges. Sound waves are produced by oscillating tuning forks. How are these waves similar?

A they are both longitudinal waves.

B they are both transverse waves.

C they both have the same frequency as their respective sources.

D they both require a medium to travel through.(Total 1 mark)

9. Two points on a progressive wave differ in phase by 4

π radian. The distance between them is

0.50 m. The frequency of the oscillations is 10 Hz. The maximum speed of the wave is

A 2.50 m s–1

B 5.00 m s–1

C 12.5 m s–1

D 40.0 m s–1

(Total 1 mark)

10. A loudspeaker emits a sound wave of wavelength 0.66 m. The diagram shows how displacement varies with distance from the loudspeaker at one instant of time.

d i s p l a c e m e n t

d i s t a n c e f r o ms o u r c e

AB C

D

(a) Which letter indicates the wavelength of the sound wave?

.....................................................................................................................................(1)

(b) Sound travels at 330 m s–1 in air. Calculate the period of the wave.

.....................................................................................................................................

.....................................................................................................................................

Period = ..........................(3)

(Total 4 marks)

11. State two conditions necessary for total internal reflection to occur at an interface between air and water.

Condition 1 ............................................................................................................................

...............................................................................................................................................

Condition 2 ............................................................................................................................

...............................................................................................................................................(Total 2 marks)

12. (a) Explain with the aid of diagrams why transverse waves can be polarised but longitudinal ones cannot be polarised.

.....................................................................................................................................

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.....................................................................................................................................(3)

(b) Describe with the aid of a diagram how you could demonstrate that light can be polarised.

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.....................................................................................................................................(3)

(Total 6 marks)

13. A ray of light travelling in air, strikes the middle of one face of an equilateral glass prism as shown.

State what happens to the following properties as the light goes from the air into the glass.

Frequency ..............................................................................................................................

Wavelength ............................................................................................................................

Speed .....................................................................................................................................(Total 3 marks)

14. The graph shows how the current in a 9 V filament lamp varies during one second after it has been turned on.

3

2

1

00 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0

t i m e / s

c u r r e n t / A

(a) A student wishes to carry out an experiment to verify these results. Explain why using a sensor and computer is a sensible option and suggest a suitable sampling rate.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(b) Explain the shape of the graph and why the filament is more likely to fail when being switched on rather than at other times.

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(Total 6 marks)

15. About 100 years ago X-rays were first used in hospitals. At that time, many of the doctors who worked with X-rays died young. Explain why this occurred and the implications it has for the use of new technology today.

...............................................................................................................................................

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...............................................................................................................................................(Total 4 marks)

16. The following apparatus is set up. When the frequency of the vibrator is 60 Hz, the standing wave shown in the diagram is produced.

1 . 5 m

l o a d

v i b r a t i o ng e n e r a t o r

(a) What is the wavelength of this standing wave?

Wavelength = ...................(1)

(b) The frequency of the vibrator is altered until the standing wave has two more nodes.Calculate the new frequency.

Frequency = ................(2)

(Total 3 marks)

17. The graph shows how the refractive index of water, n varies with wavelength λ of the light in a vacuum. The values for red and violet light are indicated.

n

1 . 3 4 2

1 . 3 3 0

4 0 0 7 0 0λ / n m

The diagram shows a mixture of red and violet light incident on an air/water interface.

r e d a n d v i o l e t l i g h t

1 0 º a i r

w a t e r

Calculate the angle of refraction for the red light.

Angle of refraction = ..........................(3)

On the diagram draw the approximate paths of the refracted rays.(2)

(Total 5 marks)

18. Below is a simplified energy level diagram for atomic hydrogen.

__________________ 0 eV

first excited state __________________ –3.4 eV

ground state __________________ –13.6 eV

(a) A free electron with 12 eV of kinetic energy collides with an atom of hydrogen. As a result the atom is raised to its first excited state. Calculate the kinetic energy of the free electron, in eV, after the collision.

Kinetic energy = ...................... eV(2)

(b) Calculate the wavelength of the photon emitted when the atom returns to its ground state.

Wavelength =................................(3)

(Total 5 marks)

19. A group of students is discussing why the resistance of the metal filament of a lamp and the resistance of an NTC thermistor respond differently to changes in temperature.

One student says that the increased vibrations of the atoms affect the conduction process. Another student says that as the temperature increases more electrons can break free of the atoms and take part in conduction.

Both students are correct. Explain how these two effects apply to the lamp and the thermistor.

...............................................................................................................................................

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...............................................................................................................................................(Total 5 marks)

20. Until the early 20th century, the wave theory of light was successful at explaining different properties of light such as reflection, refraction and diffraction. With the discovery of the photoelectric effect, scientists had a problem. The wave theory of light assumes that the energy of the wave is spread over the whole wavefront. Using the wave theory, scientists calculated that, if light of very low intensity is shone onto the metal, it should take a very long time for an electron to gain sufficient energy to break free from a metal. It was discovered that, providing the light was above a certain frequency, electrons could escape from a metal surface instantly. The new model that was introduced treated light as being made of particles called photons.

(a) What is meant by diffraction?

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(b) How did considering light as photons enable scientists to explain why electrons could be emitted instantly from a metal surface?

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(c) Explain why this effect only happens when the light is above a certain frequency.

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.....................................................................................................................................(2)

(Total 6 marks)

21. (a) Ultrasound images of the body are a useful diagnostic tool for doctors. A single transducer can be used both to send and receive pulses of ultrasound.

The diagram shows a lateral cross-section through part of the abdomen. The diagram is not to scale.

T r a n s d u c e r

A b d o m i n a lw a l l

I n t e r n a lo r g a n

2 c m 5 c m 1 0 c m

A B C D

(i) Calculate the time interval between sending out a single pulse and receiving its echo from interface B. The speed of ultrasound in the abdominal wall is

1500 m s–1.

Time interval = .......................(3)

(ii) The time between pulses being emitted by the transducer is 200 μs. At what frequency are the pulses emitted?

Frequency = ................(2)

(iii) The time interval before the echo returns from interface D is 250 μs. Suggest why this time interval will make reflections from D difficult to interpret and what could be done to overcome this problem.

...........................................................................................................................

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...........................................................................................................................

...........................................................................................................................(3)

(iv) State one reason why ultrasound rather than X-rays is now used to scan expectant mothers.

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...........................................................................................................................

...........................................................................................................................(1)

(b) Ultrasound is also used to measure blood flow in the body. It uses the Doppler shift of the reflected pulse to measure the speed of blood through the arteries of the body.

Describe the principle of this method and how it can be used to determine the speed of blood.

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.....................................................................................................................................(4)

(Total 13 marks)

22. A student sets up the following circuit to measure the internal resistance of a cell.

A

V

(a) What is wrong with his circuit diagram?

.....................................................................................................................................

.....................................................................................................................................(1)

(b) Using the correct circuit the student obtains the following results.

Current in the cellI/A

Terminal potential differenceacross the cell V/V

0.5 1.2

0.9 1.0

1.5 0.8

1.9 0.6

2.5 0.4

2.9 0.2

(i) On the grid below, plot these results and draw the line of best fit through your points.

V / V

1 . 4

1 . 2

1 . 0

0 . 8

0 . 6

0 . 4

0 . 2

00 1 2 3I / A

(3)

(ii) Use your graph to determine the e.m.f. of the cell.

e.m.f. = .........................................(1)

(iii) Use your graph to determine the internal resistance of the cell.

Internal resistance = ...................(2)

(c) The experiment is repeated with two such cells connected in series. How does the graph differ?

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 9 marks)

23. The current–potential difference characteristics of an electrical component are shown below.

C u r r e n t / m A

2 5 0

2 0 0

1 5 0

1 0 0

5 0

P o t e n t i a l d i f f e r e n c e / V

– 0 . 8 – 0 . 4 0 0 . 4 0 . 8

(a) Name the component. ....................................................................................................(1)

(b) (i) Calculate the resistance of this component when the potential difference is +0.60 V.

...........................................................................................................................

...........................................................................................................................

Resistance = .............................(2)

(ii) State its resistance when the potential difference is –0.80 V.

...........................................................................................................................(1)

(c) State a practical use for this component.

.....................................................................................................................................(1)

(Total 5 marks)

24. (a) Define resistivity.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(b) (i) The heating element used in a hairdryer consists of a long nichrome wire coiled around an insulator. The hairdryer operates at 230 V and has a power of 1.0 kW.Calculate the resistance of the heating element.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Resistance = ..................................(3)

(ii) The wire has a cross-sectional area of 1.3 × 10–7 m2. The resistivity of nichrome is

1.1 × 10–6 Ω m. Calculate the length of the nichrome wire.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Length = ..................................(3)

(iii) The nichrome wire in this heating element has a diameter of 0.41 mm.

A manufacturer wishes to make a hairdryer of the same resistance but using half the length of nichrome wire. What diameter wire must be used?

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Diameter = ..................................(2)

(Total 10 marks)

25. (a) Define the term electromotive force (e.m.f.).

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(b) A battery of e.m.f. 3.0 V is connected to a 5.0 Ω resistor with a very high resistance voltmeter placed across the resistor.

3 . 0 V

5 . 0Ω

V

(i) The very high resistance voltmeter gives a reading of 2.8 V. Show that the internal resistance of the battery is about 0.4 Ω.

...........................................................................................................................

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...........................................................................................................................(3)

(ii) A voltmeter with a resistance of 10 Ω is used instead of the original one. Calculate the combined resistance of this voltmeter and the 5.0 Ω resistor.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Combined resistance = ..................................(2)

(iii) Calculate the reading on this voltmeter.

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Voltmeter reading = ..................................(3)

(c) State and explain what the resistance of an ideal voltmeter should be.

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.....................................................................................................................................(2)

(Total 12 marks)

26. An experiment is set up to investigate how the current I in a filament lamp varies with the potential difference V across it. The components used are shown below.

A V

(a) Readings are taken over the full range from 0 V to the cell’s maximum potential difference. In the space below, draw a circuit diagram for this experiment.

(2)

(b) (i) Sketch on the axes below the shape of the graph you would expect the results to give.

(2)

(ii) Explain the shape of your graph. You may be awarded a mark for the clarity of your answer.

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(Total 8 marks)

27. A loudspeaker connected to a signal generator is set up facing a wall.

L o u d s p e a k e r

S i g n a l g e n e r a t o r

W a l l

Sound waves from the loudspeaker are reflected from the wall and a stationary wave is produced in the region between the loudspeaker and the wall.

(a) (i) Describe how you would use a small microphone, connected to a cathode ray oscilloscope, to demonstrate the presence of the stationary wave.

...........................................................................................................................

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(ii) Explain how the nodes and antinodes are produced.

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(iii) Outline how you would use this apparatus to obtain a value for the speed of sound waves in air.

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(b) (i) In principle, stationary waves produced in this way could cause problems for listeners in a concert hall. Explain why.

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(ii) In practice, the problem is not serious. Suggest a reason why.

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...........................................................................................................................(2)

(Total 11 marks)

28. (a) Magnesium has a work function of 5.89 × 10–19 J. Explain the meaning of this statement.

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.....................................................................................................................................(2)

(b) Ultraviolet radiation from an extremely faint source is incident normally on a magnesium

plate. The intensity of the radiation is 0.035 W m–2. A single magnesium atom occupies

an area of about 8 × 10–20 m2 on the surface of the plate.

(i) Show that, if the radiation is regarded as a wave motion, it should take at least 200

s for a magnesium atom to absorb 5.89 × 10–19 J of energy.

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...........................................................................................................................(3)

(ii) In practice, it is found that photoemission from the plate begins as soon as the radiation source is switched on. Explain how the photon model of electromagnetic radiation accounts for this. You may be awarded a mark for the clarity of your answer.

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(Total 9 marks)

29. (a) It is important to ensure that as little light as possible is wasted from lighthouses. In 1822 the French physicist Augustin Fresnel developed an efficient combination of lenses and prisms.

The light source is placed at the centre of this combination. This ensures that most of the light emerges as parallel rays. Figure 1 shows the whole arrangement. Figure 2 shows a cross-section of part of the arrangement with incident rays and some of the emergent rays.

Figure 1 Figure 2

C a t a d i o p t r i cp r i s m s

D i o p t r i cp r i s m s

B u l l ’ s e y el e n s

L i g h ts o u r c e

C a t a d i o p t r i cp r i s m s

D i o p t r i cp r i s m s

B u l l ’ s e y el e n s

Figure 3 shows an enlarged representation of the path of a light ray through one of the catadioptric prisms. Both reflection and refraction take place.

Figure 3

A

B

C

(i) State the necessary condition for the reflection at B.

...........................................................................................................................(1)

(ii) Describe the path of the ray shown in Figure 3 as fully as possible.

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...........................................................................................................................(2)

(b) (i) Figure 4 shows part of a diagram from an internet site showing the path of a light ray through a dioptric prism.

Figure 4

State two things that are wrong with the diagram.

1 ........................................................................................................................

...........................................................................................................................

2 ........................................................................................................................

...........................................................................................................................(2)

(ii) Add to Figure 5 to show the correct path of the light ray.

Figure 5

(3)(Total 8 marks)

30. A portable games console has the option of using a rechargeable battery unit which is recharged by connecting it to a mains adaptor. The adaptor has an input power of 2.5W at a voltage of 230 V.

(a) Calculate the adaptor’s input current when it is in use.

.....................................................................................................................................

.....................................................................................................................................

Current = .......................................................................(2)

(b) The adaptor’s output is marked as: 3 V 0.2 A 0.6 VA

(i) Explain why V A is a unit of power.

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...........................................................................................................................(1)

(ii) Calculate the efficiency of the adaptor.

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Efficiency = .......................................................................(2)

(iii) Suggest and explain a reason for the efficiency being less than 100%.

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...........................................................................................................................(2)

(c) (i) The battery unit takes a time of 6 hours to charge fully. Assuming the adaptor’s output current remains constant, calculate the amount of charge which flows from the adaptor.

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Charge = .......................................................................(2)

(ii) Calculate the work done by the adaptor.

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Work done = .......................................................................(3)

(Total 12 marks)

31. A student is thinking about how the physics of standing waves might affect music within a room.

She models a room as a completely empty cubic box with reflecting walls, as shown in Figure 1.

Figure 1

Suppose that sound waves travel across the room from side to side.

(a) The diagrams in Figure 2 are to represent three possible standing wave patterns that might form across the room. One has been drawn in.

(i) Add to Diagrams B and C two other possible patterns.

Figure 2

(2)

(ii) Mark with an X on Diagram A a place where the air particles are oscillating with the largest amplitude.

(1)

(iii) What is the name given to the place you have marked?

...........................................................................................................................(1)

(b) Assume the room is a cube of side 2.8 m. The speed of sound is 330 m s–1.

For the standing wave pattern shown in Diagram A, calculate

(i) the wavelength of the waves,

...........................................................................................................................

Wavelength = .......................................................(1)

(ii) the frequency of the waves.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Frequency = .........................................................(2)

(c) Suppose music containing the full range of audible frequencies is being played in the room.

(i) Explain why the frequency calculated in (b)(ii) might sound louder than other frequencies.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(ii) Suggest one other frequency that might also sound louder in this room.

Explain your answer.

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...........................................................................................................................(2)

(d) Now suppose music was being played in a similar but much bigger room. Explain how the frequencies of the standing waves would be different in this bigger room.

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.....................................................................................................................................(2)

(Total 12 marks)

32. Modern technology makes wide use of light-emitting devices. For many years, however, their use was limited by the lack of materials that could emit blue light efficiently.

(a) State one property of blue light which is different from red light.

.....................................................................................................................................(1)

(b) Physicists found that by adding indium to the semiconductor gallium nitride they could vary the band gap energy of the material from 2.0 to 3.4 eV and so produce a range of light from red to blue.

(i) Calculate the frequency range which corresponds to the above band gap energies.

...........................................................................................................................

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...........................................................................................................................

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...........................................................................................................................

Frequency range = ....................................................(3)

(ii) The following diagrams show the ground state and one excited state for the semiconductor when it is being used to emit red and blue light. Decide which diagram is showing the band gap of the blue light emitter and add an arrow to show the electron transition that occurs during the emission of a blue light photon.

___________________________

___________________________

___________________________ ___________________________(2)

(c) The physicists also found that after this semiconductor material had been heated strongly in nitrogen its resistivity had dropped from 106 Ω cm to just 2 Ω cm.

(i) State one advantage of this drop in resistivity when the semiconductor is in use.

...........................................................................................................................(1)

(ii) The length of a rectangular sample of the semiconductor is 0.5 cm. Its width is 0.3 cm and its thickness is 0.4 mm. Calculate the resistance across its length when the resistivity is 2 Ω cm.

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Resistance = .............................................................(3)

(Total 10 marks)

33. A rainbow is one of the most beautiful sights in nature. Each raindrop acts as a circular prism, splitting up the white light into its constituent colours. Some of the light is reflected inside the raindrop. We only see a single colour of light from any one raindrop, as shown in Figure 1.

Figure 1

W h i t e l i g h t f r o m S u n

R e d

V i o l e t

R a i n d r o p

E y eD R A W I N G N O T T O S C A L E

Only the red light leaves this raindrop at the correct angle to reach the observer’s eye.Similarly, there will be another raindrop in which only the violet light leaves at the correct angle to be seen by the observer. This is why a rainbow appears as a range of colours.

(a) On Figure 1 label an angle of incidence with an i and an angle of refraction with an r.(2)

(b) The refractive index of water for red light is 1.3. Calculate the angle of refraction when a ray of red light enters the raindrop at an angle of incidence of 27°.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Angle of refraction = ................................................(2)

(c) (i) State what is meant by critical angle.

...........................................................................................................................

...........................................................................................................................(1)

(ii) Calculate the critical angle for a raindrop.

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Critical angle = .........................................................(2)

(d) A ray of light hits the back of a raindrop as shown in Figure 2. Measure the angle of incidence at this back surface and complete Figure 2 to show what will happen to the ray of light.

Figure 2

Angle of incidence = ................................................(4)

(e) Figure 1 shows that red light is refracted less than violet light by the raindrop.Comment on the refractive index of water for red light compared to that for violet light.

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 12 marks)

34. The current I in a conductor of cross-sectional area A is given by the formula

I = n A Q v

where Q is the charge on the charge carrier.

(a) State the meanings of n and v.

n: .................................................................................................................................

v: ..................................................................................................................................(2)

(b) Show that the equation is homogeneous with respect to units.

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.....................................................................................................................................(3)

(c) Two pieces of wire A and B are made of the same material but have different diameters. They are connected in series with each other and a power supply.

(i) Which terms from the above equation will be the same for both wires?

...........................................................................................................................(1)

(ii) The diameter of A is twice that of B. Calculate the ratio vA : vB.

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...........................................................................................................................

...........................................................................................................................(2)

(Total 8 marks)

35. A and B are two lamps.

(a) Lamp A is rated at 12 V, 24W. Calculate the current in the lamp when it operates at its rated voltage.

.....................................................................................................................................

Current in lamp A= ..............................(2)

(b) Lamp B is rated at 6.0 V. When it operates at its rated voltage, the current in it is 3.0 A.

Lamps A and B are connected in a circuit as shown below. The values of R1 and R2 are chosen so that both lamps operate at their rated voltage.

1 5 V

R

A

RB

V

1

2

(i) State the reading on the voltmeter.

...........................................................................................................................(1)

(ii) Calculate the resistance of R2.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Resistance of R2 = ..............................(3)

(iii) Calculate the current in R1.

...........................................................................................................................

Current in R1 = ..............................(1)

(iv) Calculate the potential difference across R1.

...........................................................................................................................

Potential difference = ..............................(1)

(v) Calculate the resistance of R1.

...........................................................................................................................

...........................................................................................................................

Resistance of R1 = ..............................(1)

(Total 9 marks)

36. A cell of e.m.f. ε and internal resistance r is connected in a circuit with a resistor of resistance R. The current in the circuit is I.

ε

r

R

I

(a) Using the symbols in the diagram, write down a formula for

(i) the rate of conversion of chemical energy in the cell,

...........................................................................................................................

(ii) the power dissipated in the resistor of resistance R,

...........................................................................................................................

(iii) the power dissipated in r.

...........................................................................................................................(3)

(b) Use these formulae to write an equation based on conservation of energy in the circuit.

.....................................................................................................................................(1)

(c) The current I in the above circuit is given by the formula I = ε /(R + r). A laboratory E.H.T. supply is designed to produce a maximum potential difference of 5 kV. Give a typical value for the internal resistance of this supply and explain why it has this value.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................(3)

(Total 7 marks)

37. Two point sources, S1 and S2, emit waves of equal amplitude and frequency. The diagram, which is full size, shows the positions of successive crests of each wave at one particular instant of time.

S

S

A

B

QP

C r e s t

1

2

(a) (i) How can you tell from the diagram that the speed of the waves is the same everywhere?

...........................................................................................................................

...........................................................................................................................(1)

(ii) The frequency of the waves is 40 Hz. Use information from the diagram to determine their speed.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Speed = ...........................................................(3)

(b) On the diagram, draw a line joining points where the waves from S1 have travelled one wavelength further than the waves from S2. Label this line X.

(1)

(c) The waves from the two sources superpose.

(i) Describe and explain the result of this superposition along line PQ.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

(ii) Tick the appropriate boxes in the table to show what is observed at the points marked A and B in the diagram.

What is observed

Point Constructiveinterference

Destructiveinterference

Neither

A

B

(2)(Total 10 marks)

38. (a) The maximum wavelength of electromagnetic radiation which can release photoelectrons

from the surface of caesium is 6.5 × 10−7 m.

(i) State the part of the electromagnetic spectrum to which this radiation belongs.

...........................................................................................................................(1)

(ii) Show that caesium has a work function φ of about 3 × 10−19 J.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(b) The caesium cathode of a photocell is illuminated by radiation of frequency f. The circuit shown is used to measure the stopping potential Vs for a range of frequencies.

M o n o c h r o m a t i cr a d i a t i o n

P h o t o c e l l

A n o d e

C a t h o d e

V

μ A

(i) Explain what is meant by the term stopping potential.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(ii) The experiment is repeated, using different photocells, to measure the stopping potentials of calcium and beryllium. The graph shows how the stopping potentials Vs for all three metals vary with frequency f.

C a e s i u m

C a l c i u m

B e r y l l i u m

V

f

s

Use the relationship

hf = eVs + φ

to explain why all three graphs are parallel.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 7 marks)

39. A gardener installs a solar powered fountain in a sunny part of his garden. He has the following data about the solar panel from the manufacturer.

Under best conditions:

voltage across terminals 12.0 Vpower available 5.9 W

The solar panel provides power to a water pump.

(a) (i) Calculate the maximum current in the pump. Assume that the resistance of the connecting cable is negligible.

...........................................................................................................................

...........................................................................................................................

Current = ..........................................................(2)

(ii) Show that the electrical resistance of the pump is about 24 Ω.

...........................................................................................................................

...........................................................................................................................(2)

(b) He decides to install another identical fountain in a shady area of the garden. He has to place the solar panel some distance away from the pump so that it is in the sunlight.He then uses a much longer connecting cable. The connecting cable to this pump has a total resistance of 2.0 Ω. The circuit is equivalent to that shown below.

2 . 0Ω

P u m p1 2 . 0 V

Calculate

(i) the current in this circuit

...........................................................................................................................

...........................................................................................................................

Current = ..........................................................(2)

(ii) the power available to the pump.

...........................................................................................................................

...........................................................................................................................

Power = ............................................................(2)

(c) State one way in which the power available to the pump in the shady area could be improved. The positions of solar panel and fountain cannot be changed.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................(1)

(Total 9 marks)

40. (a) Light changes direction when it passes from air to water.

(i) Name the process of light changing direction in this way.

...........................................................................................................................(1)

(ii) Explain why this process takes place.

...........................................................................................................................

...........................................................................................................................(1)

(b) The diagram represents some fish under water and a butterfly above the water.

(i) Draw a ray to show the path of light travelling from the butterfly to the eye of fish B.

(2)

(ii) Explain what is meant by critical angle.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(iii) Explain how rays from fish A could reach the eye of fish B along two different paths. Add rays to the diagram to illustrate your answer.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(4)

(Total 10 marks)

41. Many species of bat detect their prey using ultrasound.

(a) What is meant by ultrasound?

.....................................................................................................................................(1)

(b) A bat emits short pulses of ultrasound up to 200 times each second. These pulses reflect off the prey and are detected by the bat.

(i) Explain why the bat uses pulses rather than a continuous beam of ultrasound.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

(ii) Suggest why a high rate of pulses is important for the bat’s success in hunting.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(c) The bat can detect any object whose size is at least as large as the wavelength of the emitted ultrasound. Calculate the size of the smallest object which can be detected for emitted ultrasound of maximum frequency 70 kHz.

Speed of ultrasound in air = 340 m s–1.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Size = .......................................................(2)

(d) A bat detects a moth 0.5 m away. Calculate the time between the bat emitting a pulse and detecting the reflected pulse from the moth.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

Time = .....................................................(2)

(e) As the moth moves away from the bat the ultrasound is reflected with a different frequency from that emitted.

Describe how the frequency of the reflected pulse changes as the moth moves away from the bat and how this relates to the movement of the moth.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................(2)

(Total 9 marks)

42. (a) Use a diagram to show what is meant by diffraction.

(2)

(b) X-ray diffraction images such as the one shown below led scientists to the first understanding of the structure of DNA. The image shown is a negative on photographic film. The dark bands correspond to maximum X-ray detection.

Figure 1

Use diagrams to explain how two X-ray waves overlap to produce maximum intensity.

(2)

(c) State two pieces of information about the structure of DNA that can be deduced from Figure 1.

1 ..................................................................................................................................

2 ..................................................................................................................................(2)

(d) Electrons can also be used to produce diffraction patterns and hence to study materials in this way.

What does this tell you about the behaviour of electrons when passing through such materials?

......................................................................................................................................(1)

(Total 7 marks)

43. A student carries out an experiment to investigate the refraction of light as it passes from glass into air. He shines a ray of light through a glass block and into the air as shown.

A i r

G l a s s

X

(a) (i) Add to the diagram to show i the angle of incidence and r the angle of refraction.Measure these two angles.

i = .........................................

r = .........................................(3)

(ii) Hence, calculate the refractive index from air to glass aμg.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

aμg = ............................................(2)

(b) At X, some of the light takes a path different from that shown on the diagram. Add another ray to the diagram showing the path of this light.

(1)

(c) The student increases the angle of incidence and notices that, above a certain angle, the light no longer passes into the air. Explain this observation.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................(2)

(d) Determine the largest angle of incidence which allows the light to pass into the air from this block.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

Angle = ....................................................(2)

(Total 10 marks)

44. Listed below are five physical quantities.

charge current potential difference resistance resistivity

Select from this list the quantity that fits each description below. You may use each quantity once, more than once or not at all.

(i) A quantity which can be measured in joules per coulomb.

.....................................................................................................................................

(ii) A quantity which equals the product of two other quantities in the list.

.....................................................................................................................................

(iii) A quantity which equals the rate of change of another quantity in the list.

.....................................................................................................................................

(iv) A base quantity in the SI system.

.....................................................................................................................................(Total 4 marks)

45. (a) A thermistor has a negative temperature coefficient. Explain with reference to the equation I = nAQv what happens to its resistance when its temperature increases.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(b) This thermistor is connected as shown in the diagram. Assume the battery has negligible internal resistance.

V

A

This circuit can be used as an electrical thermometer to monitor the temperature of a water bath.

(i) State how each meter responds when the temperature of the water is decreased.

Ammeter: ..........................................................................................................

Voltmeter: .........................................................................................................(2)

(ii) Which meter is used to indicate temperature?

...........................................................................................................................(1)

(iii) State another assumption that you made.

...........................................................................................................................(1)

(Total 7 marks)

46. The graph shows the I–V characteristics for two conductors. One is a length of nichrome wire and the other is the tungsten filament of a lamp.

C u r r e n t/ A

P o t e n t i a l d i f f e r e n c e / V

t u n g s t e nf i l a m e n t

n i c h r o m ew i r e

2 . 0

1 . 5

1 . 0

0 . 5

0 2 4 6 8 1 0

(a) Making reference to Ohm’s law, explain the shape of the tungsten filament graph.You may be awarded a mark for the clarity of your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(4)

(b) (i) Calculate the resistance of the tungsten filament when the potential difference across it is 8.0 V.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Resistance = ...............................(2)

(ii) Both conductors are connected in parallel with an 8.0 V supply. Calculate the current that will be drawn from the supply.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Current = ...............................(2)

(Total 8 marks)

47. A heater used on the rear window of a car consists of five strips of a resistive material joined as shown in the diagram.

When it is in use, the potential difference applied to the heater is 12 V and the heater generates 32 J of energy each second.

(a) (i) Calculate the total resistance of the heater.

...........................................................................................................................

...........................................................................................................................

Total resistance = ...............................(2)

(ii) Calculate the resistance of a single strip.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Resistance = ...............................(2)

(b) Each strip has a cross-sectional area of 4.0 × 10–8 m2 and is made from a material of

resistivity 1.1 × 10–6 Ω m. Calculate the length of each strip.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

Length = ...............................(3)

(c) The car manufacturer wants the rear window heater to be more powerful. Explain how this could be achieved without altering the dimensions of the individual strips or the potential difference across them.

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

(Total 9 marks)

48. (a) Define the e.m.f. of a battery.

................................................................................................................................

................................................................................................................................(1)

(b) (i) A battery of e.m.f. ε and internal resistance r is connected into a circuit as shown below.

ε r

V

4 . 0Ω

When the switch is open the voltmeter reads 12.0 V and when the switch is closed it reads 8.0 V. Calculate the current in the circuit when the switch is closed.

...........................................................................................................................

...........................................................................................................................

Current = ...............................(2)

(ii) Determine the value of r.

...........................................................................................................................

...........................................................................................................................

r = ...............................(2)

(iii) The switch remains closed. Calculate the power dissipated in the 4.0 Ω resistor.

...........................................................................................................................

...........................................................................................................................

Power = ...............................(2)

(iv) Calculate the energy wasted in the battery in five minutes.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Energy = ...............................(3)

(Total 10 marks)

49. (a) Describe how you would demonstrate that light waves can be polarised. Include a diagram of the apparatus that you would use. Describe fully what you would observe.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(5)

(b) State why it is not possible to polarise sound waves.

.....................................................................................................................................(1)

(Total 6 marks)

50. (a) The diagram shows three possible stationary waves on a string of length 1.20 m stretched between fixed points X and Y.

A

B

C

D i s t a n c e / m

0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0 1 . 2

Y

Y

Y

X

X

X

(i) Wave A has a frequency of 110 Hz.

Complete the table below to show the wavelengths and frequencies of the three waves.

Wave Wavelength / m Frequency / Hz

A 110

B

C

(3)

(ii) Each of the waves has nodes at X and Y. Explain why these points must be nodes.

...........................................................................................................................

...........................................................................................................................(1)

(b) There is a similarity between the behaviour of the string in part (a) and that of the electron in a hydrogen atom. Electron states can be represented by stationary waves which have to fit inside the atom.

Stationary waves with greater numbers of nodes represent electrons in higher energy levels. Explain why this is the case.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 6 marks)

51. The table gives information about two beams of monochromatic light.

Intensity /

Wm−2Colour

Beam A 6.0 red

Beam B 0.2 blue

Each beam is shone in turn onto a barium plate. Beam B causes photoemission but beam A does not. A student says that this is because “the blue beam is more energetic than the red beam”.

(a) In one sense the student’s statement is correct. In another sense the statement is incorrect. Explain how it is:

correct

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

incorrect

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(b) Barium has a work function of 3.98 × 10–19 J.

(i) Explain the meaning of the term work function.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(ii) Calculate the photoelectric threshold frequency for the barium plate.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Threshold frequency = ......................................(2)

(Total 7 marks)

52. The diagram shows the lowest three energy levels of atomic hydrogen.

C

B

A– 1 3 . 6

– 3 . 4

– 1 . 5

E n e r g y / e V

(a) Excited hydrogen atoms can emit light of wavelength 656 nm. By means of a suitable calculation, determine which transition between energy levels is responsible for this emission.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Transition: from level ............ to level .............(4)

(b) The spectrum of light from the Sun contains a dark line at a wavelength of 656 nm. With reference to the energy level diagram, explain how this line is produced. You may be awarded a mark for the clarity of your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(4)

(c) In the spectrum of light received from another galaxy, the same line appears at a wavelength of 695 nm.

How can we deduce from this that the galaxy is receding from the Earth?

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 9 marks)

53. An earthquake under the ocean floor may cause a tidal wave. It has been suggested that elephants may be able to give advance warning of the arrival of such a tidal wave by detecting the seismic p-waves produced by the earthquake.

(a) P-waves travel through the Earth’s crust as longitudinal waves. Describe how longitudinal waves propagate.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(b) Some p-waves have a frequency of 9.0 Hz and a wavelength of 0.8 km.

Calculate the speed of these waves.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Wave speed = .......................................................................(2)

(c) An elephant is 2500 km from the epicentre of an earthquake. A tidal wave would take about two hours to travel this distance. Determine whether it is possible for the elephant to detect the earthquake significantly earlier than the arrival of the tidal wave.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 6 marks)

54. (a) Explain what is meant by superposition of waves.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................(2)

(b) The electron micrograph shows a small area of the surface of a copper sample.

X

Y

A

B

Electrons move over the surface and behave like waves. When a wave reaches an edge or an atom, it reflects, and a standing wave is formed.

(i) Explain how a standing wave is formed by the reflection of a wave.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

(ii) A standing wave is visible on the micrograph between atoms A and B. There are nodes at X and Y. The dark lines between X and Y show antinodes.

The distance between points X and Y on the micrograph is 4.2 × 10–9 m.Use this information to calculate the wavelength of the electron waves.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Wavelength = .................................................................(2)

(iii) Explain the meaning of the terms amplitude and antinode.

Amplitude

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

Antinode

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(Total 9 marks)

55. A student investigates the use of rechargeable cells in a torch.

The diagram shows the circuit used to obtain readings of voltage and current for the torch bulb.

A

V

The results obtained are voltage = 2.68 V, current = 0.31 A.

(a) (i) Calculate the resistance of the torch bulb.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Resistance = ...................................................................(2)

(ii) The cells form a battery with an emf of 2.80 V.

Show that the internal resistance of the battery is about 0.4 Ω.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(iii) Comment on how well these values match the necessary condition for maximum power transfer between the battery of cells and the torch bulb.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(b) Each cell is labelled: ‘capacity 2 A h’. (A h is amp hours).

(i) Show that this corresponds to a total stored charge of about 14 000 C for the battery of two cells.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(ii) Calculate the time for which the battery could maintain a current of 0.31 A in the torch bulb.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

Time = ............................................................................(2)

(c) The internal resistance of the cells increases as they are used. Explain what effect this will have on the efficiency of the system.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 12 marks)

56. Heinrich Hertz first observed the photoelectric effect in 1887. He detected a current when light fell on a metal surface. In later research scientists measured the work function φ of several metals.

(a) What is meant by work function?

..........................................................................................................................................

..........................................................................................................................................(1)

(b) To measure the work function, the scientists used a phototube, consisting of a metal cathode and anode in an evacuated tube. Light falling on the cathode produced a current in the circuit.

L i g h t f a l l i n go n c a t h o d e

P h o t o t u b e

V a c u u m V

A

Explain the production of this current. Use the terms photon and photoelectron in your explanation.

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

..........................................................................................................................................(3)

(c) State the effect on the released photoelectrons of an increase in

(i) the intensity of the light used,

...........................................................................................................................

(ii) the frequency of the light used.

...........................................................................................................................(2)

(d) Light of wavelength 4.2 × 10–7 m is shone onto the metal cathode. Calculate the photon energy.

.....................................................................................................................................

.....................................................................................................................................

Photon energy = ..........................................................................(2)

(e) The metal is sodium, with a work function of 2.7 eV. Calculate the maximum kinetic energy in eV that a photoelectron could gain from this photon.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Maximum kinetic energy = ........................... eV(2)

(f) When the potential difference between the cathode and anode was reversed the current was reduced.

(i) Why does reversing the potential difference reduce this current?

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(ii) State the stopping potential that would result in zero current being detected for the sodium metal.

...........................................................................................................................

...........................................................................................................................(1)

(Total 12 marks)

57. At night, particles in the atmosphere scatter moonlight causing it to become plane polarised.

(a) What is meant by the term plane polarised?

.....................................................................................................................................

.....................................................................................................................................(2)

(b) Scientists have discovered recently that the dung beetle can navigate using polarised moonlight. The beetles hunt for fresh dung. When they find some each beetle makes a small ball. To keep this ball for itself it needs to remove it quickly. The beetle pushes the ball along with its back legs while moving with its front legs and keeping its head down. Using the plane of the polarised moonlight as a guide lets the beetle run away in a straight line.

The beetles have sensors in their eyes which act as polarising filters.

Describe and explain the effect of rotating a polarising filter in front of a source of plane polarised light.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(c) Scientists held a polarising filter over one of the beetles as it was retreating with a dung ball. The filter changed the polarisation plane by 90°.

Suggest how the beetle responded.

.....................................................................................................................................

.....................................................................................................................................(1)

(d) Suggest what would happen to the beetles on nights when the moon is not visible.

.....................................................................................................................................(1)

(Total 7 marks)

58. Railway signals rely on a combination of resistors to trigger the correct colour of light.Figure 1 shows a simplified version of the circuit used. The relay can be considered to be equivalent to a resistor. When the potential difference across the relay is above 3 V it switches on the green signal. The signal is red when the relay potential difference is less than this value.

F i g u r e 1

1 2 V R a i l w a y t r a c k R e l a y

(a) The ratio of potential differences across the resistors in this circuit varies as the resistances change. What name is given to a circuit such as this which makes use of multiple resistors in this way?

.....................................................................................................................................(1)

(b) The variable resistor is set to 10 Ω. Τhe relay resistance is 5.0 Ω. Calculate the potential difference across the relay. Assume the railway track has negligible resistance.

.....................................................................................................................................

Potential difference = ................................................................(1)

(c) The track is laid in sections of 100 m, with a length l between the rails. Each section of track is insulated from the next section. Ballast, usually made of broken up rock, is used to support the track as shown in Figure 2.

F i g u r e 2

B a l l a s ta v e r a g e d e p t h 5 c m

l = 1 . 4 4 mb e t w e e n r a i l s

(i) The ballast has a depth of 5.0 cm and a resistivity of 3.4 × 102 Ω m. Show that the resistance of this 100 m section of ballast between the rails is about 100 Ω.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(3)

(ii) The ballast resistance is in parallel with the relay. Calculate the combined resistance due to the above section of ballast and the 5.0 Ω relay.

...........................................................................................................................

...........................................................................................................................

Resistance = ........................................................(2)

(iii) How does the value of the potential difference across the relay and ballast compare with the potential difference across the relay alone?

...........................................................................................................................

...........................................................................................................................(1)

(iv) When a train is on the track the current flows through the wheel axle from rail to rail causing a short-circuit in parallel with the relay. What would the effect be on the potential difference across the relay?

...........................................................................................................................(1)

(v) When wet the ballast resistance drops considerably and may become as small as 0.5 Ω. Explain the consequence of this drop in resistance in terms of the signal lights.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 11 marks)

59. A 240 V 60 W light bulb has a tungsten filament which has a working temperature of 2600 °C.

(a) Calculate the resistance of the tungsten filament at this temperature.

.....................................................................................................................................

.....................................................................................................................................

Resistance = ................................................(2)

(b) The filament has a cross-sectional area of 3.1 × 10–10 m2. Tungsten contains 3.4 × 1028

free electrons per cubic metre. Determine the drift speed of the electrons in the filament when the current is 0.25 A.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Drift speed = ...............................................(3)

(c) Explain fully why the resistance of a tungsten filament increases with temperature. You may be awarded a mark for the clarity of your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(4)

(Total 9 marks)

60. A student sets up the following circuit using a cell of e.m.f. ε and internal resistance r.

A

r

R

(a) Complete the equation for the total e.m.f. ε in terms of the other quantities given in the diagram.

ε =(1)

(b) He measures the current I for different values of resistance R. He then plots a graph of R against 1/I.

R / Ω

A - 11_I

/

4 0

3 0

2 0

1 0

0

- 1 0

4 8 1 2 1 6 2 0

The equation for this graph is ε

R = I

ε – r

(i) Show how this equation is derived from the one you have stated above.

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...........................................................................................................................(1)

(ii) Use the graph to determine the value for the e.m.f. of the cell. Show all your working.

...........................................................................................................................

...........................................................................................................................

E.m.f. = ...................................(2)

(iii) Show that when the external resistance is 5 Ω the power dissipated in that resistance is about 0.3 W.

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(c) The student repeats the experiment adding an identical cell in series. Draw on the graph the result of this experiment.

(3)(Total 10 marks)

61. A variable resistor consisting of a wire and sliding contact has three terminals labelled K, L and M.

Figure 1

S l i d i n g c o n t a c t

M

L

R e s i s t a n c e w i r e

K

The variable resistor is connected in series with a 6.0 V supply of negligible internal resistance, an ammeter and a 20 Ω fixed resistor.

Figure 2

A

6 . 0 V

2 0 ?

. . . . . . . . . .

. . . . . . . . . .

. . . . . . . . . .

(a) Label the terminals K, L and M on Figure 2.(1)

(b) (i) The variable resistor has a maximum resistance of 10 Ω. The resistance of the fixed resistor is 20 Ω. Determine the potential difference across the resistor when the sliding contact is at the mid-point of the variable resistor.

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Potential difference = .................................................(3)

(ii) What assumption have you made about the ammeter?

...........................................................................................................................(1)

(c) The same components can be used in a second circuit to vary the potential difference across the fixed resistor fully from 0 V to 6.0 V. Draw the circuit diagram for this potential divider arrangement.

(3)(Total 8 marks)

62. (a) Explain with the aid of a diagram why transverse waves can be plane polarised but longitudinal waves cannot be plane polarised.

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(b) (i) A filament lamp is observed directly and then through a sheet of Polaroid. Describe and explain the effect of the sheet of Polaroid on the intensity of the light seen.

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(ii) The sheet of Polaroid is now rotated in a plane perpendicular to the direction of travel of the light. What effect, if any, will this have on the intensity of the light seen?

...........................................................................................................................

...........................................................................................................................(1)

(Total 6 marks)

63. The cello is a stringed musical instrument that may be played either by stroking the strings with a bow or by plucking the strings with the fingers.

(a) One of the attached strings on the cello has a vibrating length of 0.80 m. The string is made to oscillate as a stationary wave by means of a bow and the following pattern of oscillations is seen. The position of the string at two different times is shown.

D i s p l a c e m e n to f s t r i n g

D i s t a n c ea l o n g t h es t r i n g / m

0 0 . 2 0 . 4 0 . 6 0 . 8

(i) Explain how the movement of the bow causes this wave pattern.

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(ii) Using the diagram calculate the wavelength of the wave.

...........................................................................................................................

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Wavelength = ...........................................(2)

(iii) State two differences between the wave on the string and the sound wave it produces.

1 ........................................................................................................................

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2 ........................................................................................................................

...........................................................................................................................(2)

(b) The cello string is then plucked and the waveform of the resulting sound is analysed by an oscilloscope. It is found to consist of two frequencies of different amplitudes.The frequency spectrum is shown below.

A m p l i t u d e / c m

F r e q u e n c y / H z

5

4

3

2

1

0 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0

The waveform of the 200 Hz wave has been drawn on the axes below. On the same axes sketch the waveform of the 1000 Hz wave.

T i m e / m s

D i s p l a c e m e n t / c m

0 1 2 3 4 50

1

2

3

4

- 1

- 2

- 3

- 4

- 5(2)

(Total 9 marks)

64. (a) State three conditions which must be satisfied if two waves are to produce an observable interference pattern.

1 ..................................................................................................................................

2 ..................................................................................................................................

3 ..................................................................................................................................(3)

(b) (i) Describe an experiment using microwaves to produce and detect a two slit interference pattern. You may find it useful to draw a diagram.

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(ii) The dimensions of a microwave experiment are such that the equation λ = xs/D is not valid. Explain how you would find a value for the wavelength of the microwaves from your experiment.

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(Total 9 marks)

65. The diagram shows monochromatic light falling on a photocell.

V

µ A

M o n o c h r o m a t i cl i g h t

C a t h o d e

A n o d e

The photocell is connected so that there is a reverse potential difference across the cathode and the anode.

(a) Explain the following observations.

(i) Initially there is a current which is measured by the microammeter. As the reverse potential difference is increased the current reading on the microammeter decreases.

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(ii) When the potential difference reaches a certain value Vs, the stopping potential, the current is zero.

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(b) What would be the effect on the value of the stopping potential Vs of

(i) increasing the intensity of the incident radiation whilst keeping its frequency constant

...........................................................................................................................

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(ii) increasing the frequency of the incident radiation whilst keeping its intensity constant?

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(Total 7 marks)

66. A student connects a circuit to find the resistance of a washing machine heating element.

(a) Complete the circuit diagram below and explain how he uses it to obtain the necessary measurements to calculate resistance.

P o w e r s u p p l y

H e a t i n ge l e m e n t

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(b) The following results are obtained.

Voltage = 3.00 V

Current = 0.12 A

Calculate the resistance of the element from these values.

.....................................................................................................................................

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.....................................................................................................................................

Resistance = ............................(2)

(c) The element is marked “1800 W, 230 V”.

Calculate the resistance of the element in normal use.

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Resistance = ............................(2)

(d) Explain why the two values of resistance you have calculated are different.

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(Total 8 marks)

67. Sodium street lamps are usually red when first switched on in the evening. After several minutes they take on their normal yellow colour.

In these lamps, light is emitted as a current passes through the sodium vapour. However, when the lamp is first switched on the sodium is solid, so little vapour is present until it warms up. The red colour in the first few minutes is due to neon gas which the lamp also contains.

(a) Explain how atoms in a vapour emit light.

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(b) The light appears yellow because the spectrum of the sodium is dominated by two lines

with wavelengths of 589.0 × 10–9 m and 589.6 × 10–9 m respectively.

(i) Explain what is meant by a spectral line.

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...........................................................................................................................(1)

(ii) Calculate the frequency of the light with a wavelength of 589.0 × 10–9 m.

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Frequency = ............................(2)

(c) The light emitted by neon vapour appears red. Explain why atoms of different elements produce light of different colours.

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(d) Light is a transverse wave. Explain the meaning of transverse.

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(Total 9 marks)

68. Figure 1 shows an enlargement of a small rectangular area of the surface of a compact disc (CD). It shows a series of small bumps on an otherwise smooth surface.

Figure 1

B u m p

S m o o t hs u r f a c e

The presence or absence of a bump is detected by shining laser light perpendicularly onto the disc surface. Where there is a bump, some of the light hits the top of the bump, and some hits the disc surface next to the bump.

Figure 2

1 2 5 n m

N o t t os c a l eT o d e t e c t o rL a s e r

l i g h t

D i s c s u r f a c e

The height of the bumps on the surface of the disc is 125 nm. The wavelength of the light used to read the disc is 500 nm.

(a) Explain whether the light received by the detector when a bump is present has a maximum or minimum intensity.

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(b) For this detection system to work, the light reflected from the disc must be coherent.Explain the meaning of coherent.

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(Total 4 marks)

69. A fluorescent lamp consists of a glass tube containing a small amount of mercury vapour.When the lamp is switched on the mercury atoms emit photons of ultraviolet (UV) radiation. A phosphor coating inside the tube converts this radiation into visible light.

P h o s p h o r c o a t i n g i n s i d e g l a s s

When a UV photon hits the coating it excites an electron into a higher energy level. As the electron falls back down, it emits a photon of visible light.

(a) (i) Add labelled arrows to the following electron energy level diagram for an atom of the phosphor coating, to illustrate this process. Start with the absorption of a UV photon and end with the emission of a photon of visible light.

E l e c t r o n

0

E n e r g y E /J

(2)

(ii) The visible light photon emitted has less energy than the UV photon. What has happened to the rest of the energy?

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(1)

(iii) UV radiation with wavelengths in the range 320 nm–400 nm is emitted by the mercury atoms. Show that the emitted photons have a minimum energy of about 3eV.

1nm=1 × 10–9 m

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(b) ‘Black lights’ are basically the same tubes without the phosphor coating. These have many applications; for example, they can be used to detect forgeries of old paintings, as older paints did not contain phosphors.

What difference would you see between a real painting and a forgery when viewed with a black light?

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(Total 8 marks)

70. Diamonds are one of the most beautiful but expensive jewels available today. Their beauty is due largely to the way in which they sparkle when light falls on them. The way a jewel sparkles is related to how light is reflected inside the jewel which depends upon its refractive index.

(a) (i) Diamond has a refractive index of 2.42. Show that the critical angle C for light passing from diamond into air is about 24°.

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(ii) Add appropriate normals to the following diagram at the diamond-air interface and then sketch the paths that the two light rays would follow. One of them hits the interface at an angle smaller than C, and the other at an angle greater than C.

D i a m o n d

A i r

(2)

(iii) On the above diagram label

1. an incident angle i,

2. an angle of refraction r.(2)

(iv) Explain how the amount of light reflected inside the jewel depends on the refractive index, using the terms critical angle and total internal reflection.

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(b) There have been many attempts to make imitation diamonds but they have always lacked the sparkle of the real thing. Recently, however, a semiconductor company has manufactured a mineral called moissanite. This has similar properties to diamond, but is much cheaper.

The refractive index of moissanite is about 2.67. Comment on the critical angle and hence the sparkle of this mineral compared with diamond.

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(Total 10 marks)

71. A child wants to power his model train set from a 12 V battery. He also wants to be able to control the speed of his trains.

His sister is studying Physics and suggests using the following circuit.

1 2 V R e s i s t o r

S l i d i n g c o n t a c t

T o t r a i n s e t

Y

X

She has the following materials to choose from to make the resistor.

Material Resistivity / Ω m

Copper 1.8 × 10–8

Iron 1.2 × 10–7

Constantan 4.9 × 10–7

Carbon 1.4 × 10–5

(a) The resistivity of the materials varies greatly. What type of scale could be used to plot them most easily on a graph?

.....................................................................................................................................(1)

(b) (i) She chooses a carbon rod. Explain why this is a good choice.

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(ii) The carbon rod she uses has a cross-sectional area of 3.0 × 10–6 m2 and a length of 40 cm. Show that the total resistance of the carbon rod is about 2 Ω.

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...........................................................................................................................

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(iii) Assuming that the internal resistance of the battery and the resistance of the connecting wires is negligible, state the potential difference available to the train set when the sliding contact is at:

X .................................................... Y ....................................................(1)

(iv) The total resistance of the wires connecting the battery to the resistor is about 0.5 Ω. Explain whether this would have a significant effect on the potential difference available for the train set.

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(Total 9 marks)

72. (a) (i) Write the word equation that defines potential difference.

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(ii) The unit of potential difference is the volt. Express the volt in terms of base units only.

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(b) A 6.0 V battery of negligible internal resistance is connected to a filament lamp. The current in the lamp is 2.0 A.

2 . 0 A

6 . 0 V

Calculate how much energy is transferred in the filament when the battery is connected for 2.0 minutes.

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Energy transferred = …………………………………….(3)

(Total 7 marks)

73. The current I in a conductor of cross-sectional area A is given by the formula

I = nAQv

where Q is the charge on a charge carrier.

(a) What quantities do n and v represent?

n .................................................................................................................................

v .................................................................................................................................(2)

(b) A student has a metal conductor and a plastic insulator of the same dimensions. He applies the same potential difference across each. Explain how the relative values of n for the metal conductor and plastic insulator affect the current in each.

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(c) The student connects two pieces of copper wire, A and B, in series with each other and a battery. The diameter of wire A is twice that of wire B. Calculate the ratio of the drift velocity in wire A to the drift velocity in wire B and explain your answer.

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(Total 7 marks)

74. The circuit shows a battery of negligible internal resistance connected to three resistors.

6 . 0 V

4 . 0 Ω

1 5 Ω0 . 2 4 A

I

R

1I 2

(a) Calculate the potential difference across the 15 Ω resistor.

.....................................................................................................................................

Potential difference = …………………………………….(1)

(b) Calculate the current I1 in the 4.0 Ω resistor.

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I1 = …………………………………….(3)

(c) Calculate the current I2 and the resistance R.

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I2 = …………………………………….

R = …………………………………….(3)

(Total 7 marks)

75. Graph A shows how the potential difference across a battery varies with the current supplied. Graph B shows how the current in a filament lamp varies with the p.d. across it.

1 0

8

6

4

2

0 . 5 1 . 0 1 . 5 2 . 0 2 . 5 3 . 0

I / A

V / V

g r a p h B

g r a p h A

0

(a) (i) Use graph A to determine the internal resistance and the e.m.f. of the battery.

...........................................................................................................................

...........................................................................................................................

Internal resistance = …………………………………….

e.m.f = …………………………………….(2)

(ii) The lamp is connected to the battery. Determine the current in the lamp.

...........................................................................................................................(1)

(iii) Calculate the resistance of the filament lamp when it is connected to the battery.

...........................................................................................................................

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Resistance = …………………………………….(2)

(b) (i) Draw a diagram of a circuit that would enable graph A to be plotted.

(2)

(ii) Describe how you would use this circuit to obtain the data for the graph.

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(Total 9 marks)

76. A leaf of a plant tilts towards the Sun to receive solar radiation of intensity 1.1 kW m –2, which is incident at 50° to the surface of the leaf.

I n c i d e n ts o l a rr a d i a t i o n

5 0 °

L e a f

L e a fs t a l k

(a) The leaf is almost circular with an average radius of 29 mm. Show that the power of the radiation perpendicular to the leaf is approximately 2 W.

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(b) Calculate an approximate value for the amount of solar energy received by the leaf during 2.5 hours of sunlight.

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Energy = ..........................................(2)

(Total 5 marks)

77. Photoelectrons are emitted from the surface of a metal when radiation above a certain frequency, fo, is incident upon it. The maximum kinetic energy of the emitted electronsis EK.

(a) On the axes below sketch a graph to show how EK varies with frequency f.

E K

f

(2)

(b) State how the work function, φ , of the metal can be obtained from the graph.

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.....................................................................................................................................(1)

(c) Explain why this graph always has the same gradient irrespective of the metal used.

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(Total 4 marks)

78. The diagram shows some of the energy levels of a tungsten atom.

0– 1 . 8– 3 . 0

– 1 1 . 4

– 6 9 . 6

E n e r g y / k e V

I o n i s a t i o n

(a) An excited electron falls from the –1.8 keV level to the –69.6 keV level. Show that the wavelength of the emitted radiation is approximately 0.02 nm.

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(b) To which part of the electromagnetic spectrum does this radiation belong?

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(Total 5 marks)

79. The diagrams below are taken from a description of how a laser works. Each diagram illustrates some aspect of a “two energy level system”. The system consists of an electron in an isolated atom.

A two energy level system

E 1

2

E l e c t r o n

E

Absorption

E 1

2EP h o t o n

E 1

2E

Spontaneous emission

E 1

2E

P h o t o n

E 1

2E

Stimulated emission (laser)

E 1

2EP h o t o n s

E 1

2E

P h o t o n

What is meant by energy level?

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What is a photon?

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Write down a formula in terms of E1 and E2 for the energy of the photon in the absorption diagram.

Energy = ...............................................................................................................................(1)

The laser light emitted by the stimulated emission process must have the same wavelength as the photon in the spontaneous emission diagram. Explain this.

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The laser light is said to be coherent. Explain the meaning of coherent.

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(Total 5 marks)

80. It has been suggested that tigers use infrasound – low frequency sounds inaudible to humans – to keep rivals away from their territory and to attract mates.

Sound is a longitudinal wave. Describe how sound travels through the air.

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State what is meant by frequency.

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The frequency range of the sound produced by the tigers extends down to 18 Hz. Calculate the

wavelength in air for sounds of this frequency. Speed of sound in air = 330 m s–1.

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Wavelength = ....................................(2)

(Total 6 marks)

81. Some Physics students studying standing waves decide to play a trick on visitors to their Open Evening.

They set up the apparatus shown in Figure 1 in a dark corner of their laboratory.

Figure 1

S t r i n g P u l l e y

W e i g h t s

S t r o b o s c o p i cl a m p

S i g n a lg e n e r a t o r

V i b r a t i o ng e n e r a t o r

They switch on the vibration generator and the stroboscopic lamp, which flashes on and off. The frequency of the flashing is adjusted until the illuminated portion of the string appears as in Figure 2.

Figure 2

The visitors are invited to put their fingers between the two ‘strings’ they think they see and are taken by surprise when it is impossible.

Explain how standing waves have been produced on the string.

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Mark one node with N and one antinode with A on Figure 2.(1)

Add a labelled line to Figure 2 to show the wavelength.(1)

The string vibrates at a frequency of 170 Hz. The stroboscopic lamp is flashing on and off at a frequency of 340 Hz. Explain why the string appears to be in two different positions at the same time as shown in Figure 2.

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Calculate the speed of the waves in the string.

Tension in string = 1.96 N

Mass per unit length of string = 6.00 × 10–4 kg m–1

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Speed = ....................................(2)

(Total 9 marks)

82. Radar is the use of radio waves to detect the position and speed of an object. Air traffic control uses radar in this way to track the position of aircraft.

R e f l e c t e d w a v e s

E m i t t e d w a v e s

R a d a r A n t e n n a

Diagram from: http://electronics.howstuffworks.com/radar.htm

A short pulse of high frequency radio waves is transmitted from the control tower and is reflected back from an aircraft. There is an interval of 48 µ s between the transmitted pulse and the detected echo. Show that the distance of the aircraft from the control tower is about 7 km.

[1 µ s = 1 × 10–6 s]

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Distance = ....................................(2)

Give two reasons why pulses of radio waves are needed.

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The ‘Doppler shift’ of the reflected radar signal can be used to measure the speed of the moving aircraft. Describe the principle of this method and how it can be used to determine the aircraft’s speed.

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(Total 7 marks)

83. A student carries out an experiment to determine the resistivity of iron using the circuit shown below.

V

I r o n w i r e

2 V

A

He uses iron wire with a diameter of 0.50 mm.

Show that the cross-sectional area of this wire is about 2 × 10–7 m2.

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The table shows the results he obtained.

Resistance / Ω Length / m Length ÷ area /106 m–1

0.00 0.00

0.10 0.10

0.14 0.20

0.18 0.30

0.24 0.40

0.30 0.50

0.36 0.60

0.42 0.70

0.48 0.80

Complete the third column and use the data to plot a graph of resistance against length ÷ area on the grid below.

0 1 . 0 2 . 0 3 . 0 4 . 0 5 . 0

0 . 5

0 . 4

0 . 3

0 . 2

0 . 1

0

R e s i s t a n c e / Ω

L e n g t h – a r e a / 1 0 m6 – 1..(3)

Draw the line of best fit and use this to calculate the resistivity of iron.

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Resistivity = ....................................(4)

Suggest an explanation for the anomalous results obtained in this experiment.

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(Total 11 marks)

84. When the Moon is full, bright moonlight makes it difficult for astronomers to study the stars. Moonlight is scattered by atoms in the atmosphere causing it to become plane polarised.

Draw labelled diagrams to show how the polarised light differs from unpolarised light.

Polarised light Unpolarised light(2)

Explain how an astronomer’s telescope could be adapted to overcome the problem of the bright moonlight.

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(Total 4 marks)

85. The Raman effect can be used to identify the chemical composition of solid materials in a non-destructive manner, e.g. to identify fake diamonds. When laser light is shone on a material some of the light is scattered. The scattered light will be plane polarised and some of it will have been frequency shifted (that is, it will have undergone a change in frequency). This happens when the light interacts with the vibrating atoms in the materials. Analysis of these Raman frequency shifts reveals the chemical composition of the material.

What is meant by plane polarised light?

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Some of the light will have been frequency shifted by the moving atoms. Name the phenomenon which caused the frequency shifting and briefly explain how it arises.

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The Raman frequency shifts are often measured in wavenumbers. Wavenumber is defined as

wavelength

1.

When laser light of wavelength 1064 nm is shone onto diamond, the scattered light has a Raman

wavenumber shift of +1300 cm–1.

Show that the frequency of this scattered light is about 3 × 1014 Hz.

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A student correctly remarks that if the frequency of the laser light has changed then its energy must have changed.

State which model of light is being used by this student, and explain what must have happened to the vibrating atoms in the diamond during this interaction.

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(Total 14 marks)

86. Two filament lamps are designed to work from a 9.0 V supply but they have different characteristics. The graph shows the current-potential difference relationship for each lamp.

1 . 2

1 . 0

0 . 8

0 . 6

0 . 4

0 . 2

00 1 2 3 4 5 6 7 8 9

P o t e n t i a l d i f f e r e n c e / V

L a m p A

L a m p B

C u r r e n t / A

(a) The lamps are connected in parallel with a 9.0 V supply as shown.

9 . 0 V

L a m p A

L a m p B

(i) Which lamp is brighter? Give a reason for your answer.

...........................................................................................................................

...........................................................................................................................(2)

(ii) Determine the current in the supply.

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Current = ………………………………(2)

(iii) Calculate the total resistance of the two lamps when they are connected in parallel.

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Total resistance = .................................................(2)

(b) The lamps are now connected in series to a variable supply which is adjusted until the current is 0.8 A.

L a m p AL a m p B

0 . 8 A

Compare and comment on the brightness of the lamps in this circuit.

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(Total 9 marks)

87. A student connects a 9.0 V battery in series with a resistor R, a thermistor and a milliammeter. He connects a voltmeter in parallel with the resistor. The reading on the voltmeter is 2.8 V and the reading on the milliammeter is 0.74 mA.

9 . 0 V

A

VR

(a) (i) Show that the resistance of R is approximately 4000 Ω .

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...........................................................................................................................(2)

(ii) Calculate the resistance of the thermistor.

...........................................................................................................................

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Resistance = ……………………………...(2)

(b) The thermistor is mounted on a plastic base that has steel sprung clips for secure connection in a circuit board.

T h e r m i s t o r

P l a s t i c b a s eS t e e ls p r u n g c l i p

B a r em e t a l p i n s

Another student is using an identical circuit except that the bare metal pins of his thermistor are twisted together.

T h e r m i s t o rT w i s t e d b a r em e t a l p i n s

Suggest an explanation for how the reading on this student’s milliammeter will compare with that of the first student.

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(Total 7 marks)

88. A battery of e.m.f. 6.0 V is connected to a 10 Ω resistor as shown in the circuit diagram.

6 . 0 V

1 0 Ω

V

(a) Define the e.m.f. of the battery.

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(b) When the switch is open the voltmeter reading is 6.0 V. The internal resistance of the battery is 0.40 Ω . Calculate the reading on the voltmeter when the switch is closed.

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Voltmeter reading = ………………………………(3)

(c) A second identical battery is connected in parallel with the first one. Describe and explain qualitatively what would happen to the voltmeter reading if the switch remains closed.

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(Total 8 marks)

89. A microwave generator produces plane polarised electromagnetic waves of wavelength 29 mm.

(a) (i) Calculate the frequency of this radiation.

............................................................................................................................

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Frequency = ………………………………(1)

(ii) Complete the diagram of the electromagnetic spectrum below by adding the names of the parts of the electromagnetic spectrum.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .N o t t o s c a l e

I n c r e a s i n gf r e q u e n c y V I S I B L E L I G H T

X

(2)

(iii) State a typical value for the wavelength of radiation at boundary X.

............................................................................................................................(1)

(b) (i) Explain what is meant by ‘plane polarised’.

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(ii) Describe, with the aid of a diagram, how you would demonstrate that these microwaves were plane polarised.

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(Total 10 marks)

90. The diagram shows a coulombmeter (an instrument for measuring charge) set up to demonstrate the photoelectric effect.

I n c i d e n tl i g h t

N e g a t i v e l y - c h a r g e dz i n c p l a t e

C o u l o m b m e t e r

The clean zinc plate is negatively charged. When ultraviolet light is shone onto the zinc plate, the plate discharges. The coulombmeter reading gradually falls to zero. When the experiment is repeated with red light the plate does not discharge.

(a) Explain these effects in terms of the particle theory of light. You may be awarded a mark for the clarity of your answer.

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(b) What would happen to the charged plate if

(i) the intensity of the red light were increased

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(ii) the intensity of the ultraviolet light were increased?

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(c) Zinc has a work function of 3.6 eV. Calculate the maximum kinetic energy of the photoelectrons when the zinc is illuminated with ultraviolet light of wavelength 250 nm.

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Maximum kinetic energy = ………………………(4)

(Total 10 marks)

91. A student finds the following information in the instructions for an electric iron.

Setting Fabric Temperature

• Synthetics 110 °C

• • Silk/wool 150 °C

• • • Cotton/linen 200 °C

He knows that the iron is heated by a wire filament controlled by a thermostat. The thermostat switches the current off when the required temperature is reached.

The student suggests that the filament will have a higher resistance at higher temperatures. Explain why the resistance of a metal wire would be expected to increase with temperature.

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The student investigates this for each setting by plugging the iron in until it reaches the required temperature and then unplugging it from the mains power. He then uses a laboratory d.c. power supply, ammeter and voltmeter to obtain the following results:

Setting Temperature/°C Voltage/V Current/A Resistance/Ω

• 110 5.1 0.13 39

• • 150 6.2 0.15 41

• • • 200 7.4 0.19

The resistances at 110 °C and 150 °C have been calculated.

Calculate the resistance of the filament at 200 °C.

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Resistance = ...............................................(2)

Discuss whether the results support the student’s suggestion that the filament has a higher

resistance at higher temperatures.

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The student has a power meter to find the power when the iron is plugged into the mains supply and the setting is • • (silk/wool).

The reading is 1200 W.

Calculate the voltage of the mains supply.

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Voltage = ...............................................(3)

(Total 8 marks)

92. The diagram shows some of the main components of one type of fluorescent light tube.

M e r c u r y v a p o u rE l e c t r o d e

P h o s p h o r c o a t i n g

E l e c t r o d e

When the tube is switched on a charge flows between the electrodes and the mercury atoms become excited. The mercury atoms then emit radiation.

Explain the meaning of the word excited as used above.

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Explain how the excited mercury atoms emit radiation.

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Explain why only certain wavelengths of radiation are emitted.

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Some of the radiation emitted by the mercury atoms is in the ultraviolet part of the spectrum.

Humans cannot see ultraviolet radiation, so the tube is coated with phosphor. The atoms of phosphor absorb the ultraviolet radiation and then emit visible light.

Suggest why the phosphor emits different wavelengths from the mercury.

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A typical fluorescent tube has a current of 0.15 A.

Calculate the amount of charge which flows in 20 minutes.

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Charge = ...............................................(2)

(Total 10 marks)

93. According to a study carried out by Bell Labs in New Jersey, the signal from a mobile phone could be used to detect your pulse and breathing rate. The phone does not need to be answered and so could be used to locate unconscious survivors of earthquakes.

When the phone rings, microwaves are emitted which then reflect back to the phone from different parts of the owner’s body such as the chest, heart and lungs.

The following diagram shows some of these reflected waves being displayed on the screen of a cathode ray oscilloscope.

T i m e / sµ

Explain why the microwaves are reflected off different parts of the body.

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Give two reasons why the amplitudes of the peaks vary.

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Give one reason why the time between the peaks varies.

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If the microwaves are reflected from a moving object, such as a beating heart, a Doppler shift is observed.

Explain what is meant by the term Doppler shift and how it occurs.

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Describe and explain the observed changes in the wavelength and the frequency of the detected microwave signal when the heart is contracting (moving away from the microwave source).

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(Total 9 marks)

94. Disposable battery testers are sometimes placed on the packaging of battery packs. When placed across the battery terminals, the tester changes colour, depending on the amount of current that the battery provides.

To make a battery tester, you start with a layer of conductive ink that gets wider from one side to the other. The battery terminals are placed at A and B.

1 2 3

2 c m2 c m 2 c m

B 1 . 5 c m0 . 5 c m A

C o n d u c t i v e i n k

This ink is 0.02 mm thick on one such tester. Show that the resistance of section 1 above is

about 30 Ω . The resistivity ρ of the ink is 1.6 × 10–4 Ω m.

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Section 2 is 1.0 cm wide. Determine the total resistance between points A and B.

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Total resistance = ...............................................(3)

The conductive ink is red. This is covered by a layer of thermochromic ink, which gradually changes from black to transparent when warmed.

A B

T h e r m o c h r o m i c i n k

G O O D

In use, the tester is placed across the battery terminals. Current then flows in the conductive ink. The thermochromic ink becomes transparent, allowing the colour underneath to become visible.

Why does the thermochromic ink become warm?

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If the battery is low on charge, the thermochromic ink becomes transparent only in section 1 of the tester. Explain why.

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(Total 9 marks)

95. Most physicists believe that light can behave as both a wave and a particle. Name a property of light which shows it can behave as a wave.

...............................................................................................................................................(1)

In 1916, Millikan published the results of an experiment on the photoelectric effect.This proved that light also behaves as particles.

He shone monochromatic light onto plates made of different types of metal.

What is meant by the term monochromatic?

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When the light hit the plates, photoelectrons were produced. Millikan found the potential difference that was just large enough to stop these electrons being released. He also investigated how this stopping voltage varied with the frequency of light used.

The table below shows the results of an experiment like Millikan’s using sodium as the metal plate.

Stopping voltage Vs /V Frequency of light f / 1014 Hz

0.43 5.49

1.00 6.91

1.18 7.41

1.56 8.23

2.19 9.61

3.00 11.83

On the grid below, plot a graph of Vs against f.

3 . 0

2 . 5

2 . 0

1 . 5

1 . 0

0 . 5

0

0 2 4 6 8 1 0 1 2F r e q u e n c y / 1 0 H z1 4

S t o p p i n gv o l t a g e / V

(3)

The following equation applies to the photoelectric effect:

hf = φ + eVs

where φ is the work function of the metal and e is the charge on an electron.

What information about the electrons emitted does the value of the term eVs give?

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Use your graph to determine the threshold frequency for sodium.

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Hence calculate the work function of sodium.

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Work function = ...............................................(2)

No electrons are emitted below a threshold frequency. Explain why this is so.

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(Total 12 marks)

96. A student decided to carry out an investigation using a Pulfrich refractometer. Her uncle was diabetic and she thought he would find it useful to know the sugar concentration of various drinks.

The diagram shows the refractometer she used.

S a m p l e o f d r i n k

G l a s sA i r

X

I n c i d e n tr a y

Label the critical angle C on this diagram.(1)

One of the samples studied was found to have a refractive index of 1.09 between the liquid and the glass. Show that the critical angle for light in the refractometer is about 67° for this sample.

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A black line is drawn on the glass block at position X. When looking through the glass block from different angles this black mark is not always seen. Explain why this is the case.

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These are some of the results obtained by the student.

Drink sample tested Refractive index betweenliquid and glass

Orange Squash 1.05

Summer Fruits 1.10

Which has a higher concentration of sugar, Orange Squash or Summer Fruits? Explain your answer.

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(Total 8 marks)

97. Below is a list of words associated with circuits.

Current Volt Resistance

Ohm Charge Ampere

For each of the following choose one example from the above list.

Base unit ...............................................................................

Derived quantity ...................................................................

Derived unit...........................................................................

Base quantity ........................................................................(Total 4 marks)

98. Io is one of Jupiter’s moons. Some of the electrons released from the volcanic surface of Io have

an average velocity of 2.9 × 107m s–1 towards Jupiter. The distance between Jupiter and Io is

4.2 × 105 km.

(a) Show that the time taken for these electrons to reach Jupiter is about 14 s.

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(b) In this way a current of 3.0 × 106 A is created between Io and Jupiter. Calculate the number of electrons that arrive at Jupiter every second.

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Number of electrons = ................................(2)

(c) State the direction of the current.

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(Total 5 marks)

99. The circuit diagram shows a 12 V d.c. supply of negligible internal resistance connected to an arrangement of resistors. The current at three places in the circuit and the resistance of two of the resistors are given on the diagram.

1 2 V

2 . 0 Ω4 . 0 Ω

2 . 0 A2 . 0 A

1 . 5 A

R

R

1

2

(a) Calculate the potential difference across the 4.0 Ω resistor.

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Potential difference = ..................................(1)

(b) Calculate the resistance of resistor R2.

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Resistance of R2 = ......................................(2)

(c) Calculate the resistance of resistor R1.

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Resistance of R1 = ......................................(3)

(Total 6 marks)

100. The circuit shown is used to produce a current-potential difference graph for a 12 V, 24 W filament lamp.

A

V

(a) Calculate the current in the filament lamp when the potential difference across it is 12 V.

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Current = ......................................(2)

(b) (i) Sketch a graph of current against potential difference for this filament lamp.

(2)

(ii) Explain, with reference to the filament, the shape of your graph, as the potential difference across the filament increases from 0 V to 12 V.

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(Total 8 marks)

101. (a) A student sets up a circuit and accidentally uses two voltmeters V1 and V2 instead of an ammeter and a voltmeter. The circuit is shown below.

9 . 0 V

1 0 0 Ω

V

V

1

2

(i) Circle the voltmeter which should be an ammeter.(1)

(ii) Both voltmeters have a resistance of 10 MΩ. The student sees that the reading on V2 is 0 V. Explain why the potential difference across the 100 Ω resistor is effectively zero.

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(b) The student replaces the 100 Ω resistor with another resistor of resistance R. The reading on V2 then becomes 3.0 V.

(i) Complete the circuit diagram below to show the equivalent resistor network following this change.

Label the resistor R.

9 . 0 V

(2)

(ii) Calculate the value of R.

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R = ..............................................................(3)

(Total 8 marks)

102. The table below summarises some features of the electromagnetic spectrum. Complete the table by filling in the missing types of radiation, wavelengths and sources.

Radiation Typical wavelength Source

Visible light Very hot objects

Gamma

100 mHigh frequencyelectrical oscillator

10–6 m

(Total 6 marks)

103. A stationary wave of amplitude 4.0 cm is produced by the superposition of two progressive waves that travel in opposite directions.

(a) Define the term amplitude.

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......................................................................................................................................(1)

(b) The graph below shows the positions of the stationary wave and of one of the two progressive waves at a particular instant. Apply the principle of superposition to determine the displacement of the other progressive wave at positions A, B and C on the distance axis at this same instant.

Displacement at A ........................................................................................................

Displacement at B ........................................................................................................

Displacement at C ........................................................................................................(3)

Plot these displacement values on the graph.

Hence draw one complete wavelength of this progressive wave.

D i s p l a c e m e n t / c mS t a t i o n a r y w a v e

P r o g r e s s i v e w a v e

D i s t a n c e / c mA B C

4

3

2

1

(3)(Total 7 marks)

104. (a) Explain what is meant by the term transverse wave. You may wish to illustrate your answer with the help of a simple diagram.

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.......................................................................................................................................(3)

(b) State two differences between a stationary wave and a progressive wave.

Difference 1 .................................................................................................................

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Difference 2 .................................................................................................................

......................................................................................................................................(2)

(c) Spiders are almost completely dependent on vibrations transmitted through their webs for receiving information about the location of their prey. The threads of the web are under tension. When the threads are disturbed by trapped prey, progressive transverse waves are transmitted along the sections of thread and stationary waves are formed.

Early in the morning droplets of moisture are seen evenly spaced along the thread when prey has been trapped.

D r o p l e to f w a t e r

T h r e a d

1 c m o n d i a g r a m r e p r e s e n t s0 . 2 5 c m o f t h r e a d

(i) Explain why droplets form only at these points.

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............................................................................................................................(1)

(ii) The speed of a progressive transverse wave sent by trapped prey along a thread is

9.8 cm s–1. Use the diagram to help you determine the frequency of the stationary wave.

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Frequency = ................................................(4)

(Total 10 marks)

105. The photoelectric effect supports a particle theory of light but not a wave theory of light.

Below are two features of the photoelectric effect. For each feature explain why it supports the particle theory and not the wave theory.

(a) Feature 1: The emission of photoelectrons from a metal surface can take place instantaneously.

Explanation ..................................................................................................................

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(b) Feature 2: Incident light with a frequency below a certain threshold frequency cannot release electrons from a metal surface.

Explanation ..................................................................................................................

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(Total 4 marks)

106. When a photon of sunlight is incident on a photovoltaic cell, an electron in the cell gains sufficient energy to move through a potential difference of 0.48 V.

What is a photon?

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.................................................................................................................................................(2)

Show that the energy required to move an electron through a potential difference of 0.48 V is

about 8 × 10–20J.

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Photons of sunlight typically have energy 4.0 × 10–19 J. Calculate the efficiency of conversion of the energy of the photon.

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Efficiency = ....................................................(2)

(Total 6 marks)

107. A recorder, a common musical instrument, can be modelled as a tube of air open at both ends. The air at both ends therefore remains at normal air pressure. The diagrams below show how the air molecules in the recorder are displaced at two different moments during one cycle of the fundamental note. The two moments are separated by T/2, where T is the time period.

D i s p l a c e m e n to f m o l e c u l e s

N o r m a l a i r p r e s s u r e

N o r m a l a i r p r e s s u r e

C o m p r e s s i o n

R a r e f a c t i o n

N o r m a l a i r p r e s s u r e

N o r m a l a i r p r e s s u r e

l

T2

l a t e r

Explain whether the ends of the recorder have nodes or antinodes for pressure.

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.................................................................................................................................................(2)

Write down a relationship between the length l of the recorder and the wavelength λ of the fundamental note it produces.

.................................................................................................................................................(1)

The length l of the recorder is 0.28 m. Calculate the fundamental frequency of the note it

produces. Speed of sound in air = 330 m s–1.

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Frequency = ....................................................(3)

Calculate the period T of the fundamental note.

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Period = ..........................................................(2)

State one other frequency which might be present in the note produced by this recorder. Explain your choice in terms of nodes and antinodes for pressure along the recorder.

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(Total 11 marks)

108. The following notes are taken from some laboratory instructions for using an ohmmeter to measure resistance.

• Ohmmeters should be zeroed. To do this, touch the leads together and adjust the meter to read zero ohms.

• The ohmmeter works by placing a small voltage across the resistor. The current that flows in response to this voltage determines the ohmmeter reading.

• Do not measure the resistance of a resistor while it is in a circuit.

Explain why touching the leads together allows the meter to be zeroed.

.................................................................................................................................................

.................................................................................................................................................(1)

An ohmmeter is connected across a resistor. The ohmmeter applies a voltage of 0.54 V.The current through the meter is 0.0081 A. Show that the resistance being measured is about 70 Ω.

.................................................................................................................................................

.................................................................................................................................................(2)

Explain why, when using an ohmmeter, the resistance of the resistor should not be measured while it is in a circuit.

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.................................................................................................................................................(2)

By connecting the ohmmeter across a coil of thin copper wire, temperature changes can be detected.

Explain how, as the temperature rises, changes in the copper lead to changes in the meter reading.

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.................................................................................................................................................(3)

(Total 8 marks)

109. A three-year-old child at a barbecue was heard to remark: “The trees look like jelly – they’re all wobbly”. She was looking at the trees over the top of the hot barbecue. Heated, less dense air was rising from the barbecue in uneven layers, changing the direction of the light from the trees in a varying pattern.

Name this process of changing the direction of the light by air of different densities.

.................................................................................................................................................(1)

The diagram shows a ray of light from the trunk of each tree reaching the child before the barbecue is lit.

A B C

V i e w f r o ma b o v e

C h i l d

After the barbecue is lit, a layer of hotter, less dense air is between the child and the trees.

Complete the diagram below to show a ray of light from each of the trees A, B and C reaching the child. The ray A has been started for you.

A B C

V i e w f r o ma b o v e

C h i l d

D i s t a n t t r e e s

H o t a i r

(3)

Complete the diagram below to show the apparent position of the tree trunks as viewed through the layer of hot air.

(2)

Explain why the trees look “all wobbly”.

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.................................................................................................................................................(2)

(Total 8 marks)

110. To preserve food effectively, packaging film must isolate food from bacteria in the environment. The film is thoroughly inspected for holes, but many inspection techniques can damage it.

A new technique has been developed to check the film. The film is passed between a roller electrode and a conducting liquid, in which a second electrode is placed, as shown below. The resistance between the two electrodes is measured; even a pinhole in the film can greatly reduce this resistance by filling with the liquid and creating a conducting path.

C o n d u c t i n gl i q u i d

R o l l e r e l e c t r o d e

F i l m

E l e c t r o d e

Complete the diagram above showing a circuit you could use to measure this resistance.(2)

For undamaged film the resistance measured between the electrodes is very high. Show that

when a circular hole of diameter 1.0 × 10–4 m is present and fills with the conducting liquid the resistance measured is about 170 Ω. Assume that the resistance through the liquid between the lower electrode and the film is so small it can be ignored.

Resistivity of conducting liquid = 2.7 × 10–3 Ω m, film thickness = 5.0 × 10–4 m.

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.................................................................................................................................................(3)

Using this technique, the following values of resistance were obtained.

Diameter of hole / mm Resistance / Ω

0.2 43.0

0.4 10.7

0.6 4.8

0.8 2.7

1.0 1.7

Plot a graph of resistance against diameter from these results on the grid below.

(4)

Use the graph to determine the diameter of the hole which gives a resistance of 30 Ω.

.................................................................................................................................................(1)

(Total 10 marks)

111. The screen of a laptop computer makes use of polarised light.

Draw labelled diagrams to show what is meant by unpolarised and plane polarised light.

(2)

The screen contains a polarising filter. The dark parts of an image are formed where polarised light is blocked by this filter; the light parts are where unpolarised light gets through.

As a security measure, the images on the screen can be made invisible by removing the polarising filter from the front of the screen.

State the appearance of a computer screen whose polarising filter has been removed.

.................................................................................................................................................

Explain your answer.

.................................................................................................................................................

.................................................................................................................................................(2)

The computer operator would wear glasses containing polarising lenses. The glasses can do the same job as the polarising filter. State and explain what a computer operator wearing the glasses would observe if he tilted his head from side to side while looking at the screen.

.................................................................................................................................................

.................................................................................................................................................

.................................................................................................................................................(2)

It has been suggested that this security measure could be defeated by anyone wearing a pair of simple 3-dimensional movie glasses. These have a horizontal polarising filter on one eye and a vertical filter on the other.

Comment on this suggestion.

.................................................................................................................................................

.................................................................................................................................................

.................................................................................................................................................(2)

(Total 8 marks)

112. In order to reduce the engine noise heard by a car driver, some cars are designed so that noise is also emitted by the car’s speakers. This technique is known as active noise control.

With the aid of sketch graphs showing relevant wave forms, explain how sound from the speakers can reduce the intensity of the sound heard by the driver.

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.................................................................................................................................................(Total 6 marks)

113. A student connects the circuit as shown in the diagram.

6 . 0 V

4 0 0 Ω

V

The reading on the voltmeter is 1.8 V. Calculate the current in the resistor.

...............................................................................................................................................

...............................................................................................................................................

Current = ...............................................(1)

Calculate the resistance of the thermistor.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Resistance = ........................................(2)

The graph shows how the resistance of the thermistor depends on its temperature.

3 0 0 0

2 5 0 0

2 0 0 0

1 5 0 0

1 0 0 0

5 0 0

00 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0

T e m p e r a t u r e / ° C

R e s i s t a n c e / Ω

Determine the temperature of the thermistor.

Temperature = ......................................(1)

If the e.m.f. of the supply were doubled, would the reading on the voltmeter double?

Explain your answer.

...............................................................................................................................................

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...............................................................................................................................................(3)

(Total 7 marks)

114. A student is asked to carry out an experiment to find the resistivity of the material of a length of resistance wire. Draw an appropriate circuit diagram.

(2)

List all the measurements the student should take to find the resistivity.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

How should these measurements be used to find the resistivity?

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...............................................................................................................................................(3)

Suggest two precautions the student should take to ensure an accurate result.

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...............................................................................................................................................(2)

(Total 10 marks)

115. Modern electric showers need to be very powerful because they are required to heat the water flowing through them very quickly.

The shower is connected to the electrical supply by a copper cable 15 m long. A conductor

inside the cable has a cross-sectional area of 6.0 × 10–6 m2. The resistivity of copper is 1.7 × 10–

8 Ω m. Find the resistance of the conductor.

...............................................................................................................................................

...............................................................................................................................................

Resistance = .........................................(3)

The conductors used for most electrical circuits in homes are copper but they have a smaller cross-sectional area. Suggest why the manufacturer of the shower recommends that the thicker wire is used in the shower cable.

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 5 marks)

116. A 12 V car battery is recharged by passing a current of 5.0 A through it in the reverse direction using a 15 V battery charger. The internal resistance of the charger and the battery are 0.56 Ω and 0.04 Ω respectively. The circuit used is shown below.

0 . 0 4Ω0 . 5 6Ω

B a t t e r yB a t t e r yc h a r g e r

1 2 V1 5 V

5 . 0 A

5 . 0 A

V

C h a r g i n gc u r r e n t

The terminal p.d. across the battery charger is found by solving the following equation:

Terminal p.d. = 15 V – (5.0 A × 0.56 Ω )

Determine the reading on the voltmeter.

...............................................................................................................................................(1)

Write an equivalent equation for the terminal p.d. across the battery.

...............................................................................................................................................

...............................................................................................................................................(3)

Calculate the rate at which energy is being wasted during the recharging process.

...............................................................................................................................................

...............................................................................................................................................

Rate = ..................................................(2)

Hence determine the efficiency of the recharging process.

...............................................................................................................................................

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Efficiency = ..........................................(2)

The internal resistance of this car battery is 0.04 Ω. Explain why a car battery is designed to have a very low internal resistance.

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...............................................................................................................................................(2)

(Total 10 marks)

117. A stationary wave is produced on a stretched string by a vibration generator attached to one end. The graph shows part of the wave. The two full lines represent the extreme positions of the string.

1 0

5

0

– 5

– 1 0

D i s p l a c e m e n t / m m

D i s t a n c e / m

0 0 . 1 0 0 . 2 0 0 . 3 0 0 . 4 0 0 . 5 0

State the wavelength of this wave.

.............................................................................................................................................(1)

Mark a letter A on the graph to label an antinode.(1)

The stationary wave is formed by the superposition of two waves travelling along the string in opposite directions. The frequency of the vibrator is 36.0 Hz. Calculate the speed of the travelling waves.

.............................................................................................................................................

.............................................................................................................................................

Wave speed = ......................................(2)

State the phase relationship between the two travelling waves at an antinode.

.............................................................................................................................................(1)

Determine the amplitude of each of the travelling waves.

.............................................................................................................................................

Amplitude = ........................................(1)

(Total 6 marks)

118. Four of the energy levels of a lithium atom are shown below.

E n e r g y / e V

– 1 . 8 5

– 3 . 8 4

– 4 . 5 3

– 5 . 0 2

Draw on the diagram all the possible transitions which the atom could make when going from the –3.84 eV level to the –5.02 eV level.

(2)

Photons of energy 3.17 eV are shone onto atoms in lithium vapour. Mark on the diagram, and label with a T, the transition which could occur.

(1)

One way to study the energy levels of an atom is to scatter electrons from it and measure their kinetic energies before and after the collision. If an electron of kinetic energy 0.92 eV is scattered from a lithium atom which is initially in the –5.02 eV level, the scattered electron can have only two possible kinetic energies.

State these two kinetic energy values, and explain what has happened to the lithium atom in each case. (You should assume that the lithium atom was at rest both before and after the collision.)

Kinetic energy 1 ...................................................................................................................

Explanation ..........................................................................................................................

..............................................................................................................................................

Kinetic energy 2 ...................................................................................................................

Explanation ..........................................................................................................................

..............................................................................................................................................(4)

(Total 7 marks)

119. The photograph shows a laboratory machine for illustrating a sinusoidal transverse wave.Beside the machine is a rule. (You may make marks on the photograph if you wish.)

Find a value for the wavelength of the waves.

...............................................................................................................................................

...............................................................................................................................................

Wavelength = .......................................(2)

Find a value for the amplitude of the waves.

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Amplitude = ..........................................(2)

The machine is operated so that every rod along the wave moves up and down through a complete cycle every 2 s. Calculate the frequency of the waves.

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Frequency = ............................................(1)

What is meant by a transverse wave?

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...............................................................................................................................................(2)

Discuss whether this machine would be helpful in illustrating how a sound wave travels.

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(Total 10 marks)

120. A student does some measurements on two light-emitting diodes (LEDs). She measuresthe current I through them at a series of voltages V. Her results are shown in the table.

V/V Green LED I/mA Red LED I/mA

1.1 0 0

1.2 0 0

1.3 0 0

1.4 0 0.01

1.5 0 0.05

1.6 0 0.33

1.7 0.02 3.89

1.8 0.20

1.9 1.46

2.0 5.12

Complete the circuit diagram below to show a circuit that she could have used to obtain these results.

(3)

For both LEDs, the current varies in a similar way. Describe in words this variation.

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...............................................................................................................................................(3)

Discuss whether the LEDs obey Ohm’s law.

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...............................................................................................................................................(2)

Calculate the resistance of the green LED when it has 1.9 V across it.

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Resistance = ..........................................(2)

Calculate the power dissipated by the red LED when it has 1.7 V across it.

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Power = ................................................(2)

(Total 12 marks)

121. Rainbows are caused when sunlight is dispersed by raindrops. The different colours follow separate paths.

The diagram shows some of the rays of light passing through a raindrop.

S u n l i g h t

V i o l e t

R e dR a i n d r o p

A

B

Name the process which occurs at A.

...............................................................................................................................................(1)

The ray at B is actually only partially reflected at the surface of the water. Continue the ray to show the path of the red light which is not reflected.

(1)

Explain the condition that would be required to prevent the red light from emerging at B.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Light changes its direction at A because of a change of speed on entering the water.

Red light has a frequency of 4.2 × 1014 Hz. Calculate its wavelength in a raindrop.

Speed of light in water = 2.2 × 108 m s–1.

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Wavelength = .......................................(2)

(Total 6 marks)

122. An advertisement for sunglasses claims:

ELIMINATE GLARE WITH POLARISING SUNGLASSES

Glare is created when bright sunlight reflects off horizontal surfaces, suchas roads. Polarising sunglasses are special sunglasses that eliminate99.9% of this type of glare by only letting in light at a certain angle or ina certain direction.

Use diagrams to explain the difference between polarised and unpolarised light.

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...............................................................................................................................................(2)

In physics terms what does the advertisement mean by ‘light at a certain angle or in a certain direction’?

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...............................................................................................................................................(1)

What is the evidence in this advertisement that ‘glare’ consists of polarised light?

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Normally sunglasses are worn so as to eliminate glare. Explain what would happen if the sunglasses were turned through 90°.

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(Total 6 marks)

123. State the word equation that is used to define charge.

...............................................................................................................................................

...............................................................................................................................................(1)

Define potential difference.

...............................................................................................................................................

...............................................................................................................................................(1)

A 9.0 V battery of negligible internal resistance is connected to a light bulb.

Calculate the energy transferred in the light bulb when 20 C of charge flows through it.

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Energy = .....................................................(2)

(Total 4 marks)

124. A polythene rod was negatively charged by rubbing it with a cloth. The rod was then stroked several times across the metal cap of a meter used for measuring charge.

C h a r g e dp o l y t h e n e r o d

M e t e r

The initial reading on the meter was zero.

After 3.8 s the final reading was –6.4 × 10–8 C.

Calculate the number of electrons that were transferred to the metal cap.

...............................................................................................................................................

...............................................................................................................................................

Number of electrons = …………………………(3)

Calculate the average rate in C s–1 at which charge was transferred to the metal cap.

...............................................................................................................................................

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Rate = …………………………………… C s–1

(2)

State the base unit for the rate of flow of charge.

...............................................................................................................................................(1)

(Total 6 marks)

125. A light-emitting diode (LED) is a diode that emits light when it conducts. Its circuit symbol is

A student connects the circuit shown below.

L E D

S l i d i n g c o n t a c t

+ 5 . 0 V

A

0 VB

1 k

V

She notices that the reading on the high resistance voltmeter remains at 0 V as she slides the contact between terminals A and B.

Explain this observation as fully as you can.

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...............................................................................................................................................(2)

The student then disconnects the LED and reconnects the circuit as shown below. She intends to vary the intensity of the light emitted by the LED by sliding the contact between terminals A and B.

S l i d i n g c o n t a c t

+ 5 . 0 V

A

0 VB

1 k

V

L E D

The student cannot detect any light emitted by the LED. Briefly explain why the LED is so dim.

...............................................................................................................................................

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...............................................................................................................................................(2)

Draw the circuit that the student should have connected using this apparatus in order to vary the brightness of the LED and measure the potential difference across it.

(3)(Total 7 marks)

126. A solar cell is a device that generates a potential difference when certain wavelengths of the electromagnetic spectrum are incident on it.

The circuit symbol for a solar cell is

The solar cell is used in a circuit with a variable resistor, an ammeter and a voltmeter. Readings of current I in the circuit and the terminal potential difference V across the solar cell are used to plot a graph of I against V. Draw a suitable circuit diagram.

(2)

The graph shows a set of results obtained in this way. The intensity of the light incident on the cell remained constant while the readings were obtained.

0 . 8

0 . 6

0 . 4

I / A

V / V

0 . 2

00 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5 0 . 6

X

Calculate the power output of the cell at the point marked X on the graph.

...............................................................................................................................................

...............................................................................................................................................

Power = .........................................................(2)

Describe the variation of the power output of the cell as the current increases from zero to its maximum value.

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...............................................................................................................................................(3)

State the e.m.f. of the cell.

...............................................................................................................................................(1)

Calculate the internal resistance of the cell when it is operating under the conditions represented by point X.

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Internal resistance = ......................................(2)

(Total 10 marks)

127. Tick whether the following statements are true or false. In each case explain your reasoning.

Statement 1

When a battery is connected across a thick wire in series with a thin wire of the same material, the electrons move faster through the thick wire.

T r u e F a l s e

Explanation

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...............................................................................................................................................(3)

Statement 2

When a battery is connected across a high resistance in parallel with a low resistance, more power is dissipated in the low resistance.

T r u e F a l s e

Explanation

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(Total 6 marks)

128. Describe, with the aid of a diagram, an experiment to demonstrate stationary waves using microwaves.

...............................................................................................................................................

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...............................................................................................................................................(4)

Using the idea of wave superposition, explain what is observed in your experiment.

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...............................................................................................................................................(2)

Describe how you could use the experiment to measure the wavelength of microwaves.

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(Total 8 marks)

129. A monochromatic light source is placed 120 mm above the cathode of a photocell.

W i r e a n o d e1 2 0 m m

P h o t o c e l l

M e t a l c a t h o d e

M o n o c h r o m a t i c l i g h t s o u r c e

A potential difference is applied between the cathode and the anode of the photocell and the sensitive ammeter detects the current.

V

p A

The table below shows the currents which are obtained with this apparatus for two different intensities and two different wavelengths of light, using two different cathode materials. Work function energies are given.

Wavelengthof incident

radiation /nm

Cathodematerial

Workfunction /eV

Photocurrent /Awhen intensity

of incidentradiation is

1 W m–2 5 W m–2

320 Aluminium 4.1 0 0

640 Aluminium 4.1 0 0

320 Lithium 2.3 0.2 × 10–12 1.0 × 10–12

640 Lithium 2.3 0 0

Show that the incident photons of λ = 320 nm and λ = 640 nm have energies of approximately 4 eV and 2 eV respectively.

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...............................................................................................................................................(4)

Account for the photocurrent readings shown in the table.

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...............................................................................................................................................(3)

Calculate the stopping potential for the photoelectrons released by lithium when irradiated by light of wavelength 320 nm.

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Stopping potential = ........................................(2)

(Total 9 marks)

130. Diagram (i) represents part of a stretched spring. Diagram (ii) represents the same section of the spring at one instant of time when a sinusoidal longitudinal wave is travelling along it.

W a v e s p e e d 2 . 0 0 m s– 1

D i s t a n c e / m

( )i

( )i i

0 . 0 0 0 . 2 0 0 . 4 0 0 . 6 0 0 . 8 0 1 . 0 0 1 . 4 01 . 2 0

Use the diagram (ii) to determine the wavelength of the longitudinal wave.

...............................................................................................................................................

Wavelength = ........................................(1)

The wave speed is 2.00 m s–1. Calculate the frequency of this wave.

...............................................................................................................................................

Frequency = ...........................................(1)

Describe qualitatively the motion of an individual coil of this spring as the longitudinal wave travels along the spring.

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...............................................................................................................................................(3)

(Total 5 marks)

131. In the film ‘Contact’, astronomers listen for signals from space as part of the Search for Extra-Terrestrial Intelligence (SETI).

The discovery of a signal is followed by this dialogue between two astronomers.

Astronomer 1: “What’s the frequency?”

Astronomer 2: “4.4623 gigahertz – that’s hydrogen times π.”

By ‘hydrogen’, she was referring to the ‘21 cm’ line in the spectrum of atomic hydrogen, a wavelength used by radio astronomers because it is not absorbed by the Earth’s atmosphere.

(1 gigahertz = 1 × 109 Hz)

Explain how hydrogen atoms emit radiation.

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...............................................................................................................................................(2)

Why do hydrogen atoms emit radiation at specific frequencies?

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...............................................................................................................................................(3)

Show that the statement by astronomer 2, “4.4623 gigahertz – that’s hydrogen times π” is consistent with a hydrogen wavelength of about 21 cm.

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(Total 8 marks)

132. A student models a stage lighting system using a circuit-drawing computer package and a spreadsheet. He starts with a power supply of e.m.f. 120 V, and internal resistance 15 Ω. He assumes that each lamp has fixed resistance 60 Ω. He is interested in the effect of turning on the lamps one at a time, so that the number of lamps switched on increases from one to six. His circuit and part of his spreadsheet are shown below.

V

A

X

A B C D E

1 Number oflamps

switched on

Netresistanceof lamps/Ω

Totalcurrent

fromsupply/A

p.d. acrosslamps/V

Power toall

lamps/W

2

3 1 60 1.6 96 154

4 2 30 2.7 80 213

5 3 20 3.4 69 235

6 4 15 4.0 60 240

7 5 12 4.4 53

8 6 10 4.8 48 230

The student has assumed that the voltmeter would have no effect on any of the values he has calculated. Explain why this is an appropriate assumption.

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...............................................................................................................................................

...............................................................................................................................................(1)

When 6 lamps are on (row 8), how much current flows through lamp X?

...............................................................................................................................................

...............................................................................................................................................

Current through X = ...............................................(1)

Calculate the value missing from cell E7.

...............................................................................................................................................

...............................................................................................................................................

Value = ..................................................................(1)

The lamp marked X is the first to be switched on. Explain how lamp X would appear as successive lamps are switched on.

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...............................................................................................................................................(3)

What would be a suitable formula for calculating cell C6?

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...............................................................................................................................................(2)

Comment on how the internal resistance of the power supply affects the way in which the values in column E vary.

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...............................................................................................................................................(2)

(Total 10 marks)

133. A student records the note from one string of a piano onto a computer software package. The waveform of the note is shown in figure 1. The frequency spectrum of the note is shown in figure 2. This shows the relative amplitudes of the lowest ‘fundamental’ frequency and four further frequencies (overtones) that produce the note.

0 . 8 2 0 0 . 8 2 5 0 . 8 3 0 0 . 8 3 5 0 . 8 4 0

F i g u r e 1

T i m e / s

0 1 0 0 0 2 0 0 00 . 0

0 . 1

0 . 2

0 . 3

0 . 4

0 . 5

0 . 6

0 . 7

0 . 8

0 . 9

1 . 0

F i g u r e 2

R e l a t i v ea m p l i t u d e

F r e q u e n c y / H z

By reading from the frequency spectrum (figure 2) state

(i) the fundamental frequency of the note

.....................................................................................................................................(1)

(ii) the frequencies of the first three overtones

.....................................................................................................................................(2)

Comment on any pattern you see in these frequencies.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

From the waveform trace (figure 1) make the best measurement you can of the period. Show how you reach your answer.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Period = ..................................................................(2)

Use this value for the period to calculate the frequency.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Frequency = ........................................................(2)

(Total 9 marks)

134. The diagrams below illustrate the formation of a rainbow. Figure 1 shows the general arrangement and Figure 2 shows the path of a ray through a raindrop.

Figure 1

S u n ’ s r a y s

R a i n d r o p

R a i n b o w

O b s e r v e r

Figure 2

O X

Where the ray enters the raindrop in Figure 2, mark the angle of incidence i and the angle of refraction, r. The centre of the raindrop is labelled O.

(2)

Figure 2 is drawn to scale. By taking suitable measurements, show that the refractive index of water is about 1.3.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Calculate the critical angle for water.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Critical angle = .................................................(2)

Using another measurement from Figure 2, explain whether the reflection of the ray at X is partial or total.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

A rainbow consists of a spectrum of colours. What does this suggest about the refractive index of water?

...............................................................................................................................................

...............................................................................................................................................(1)

(Total 10 marks)

135. Explain what is meant by

(i) refraction

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

(ii) diffraction.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

Out at sea, waves follow the direction of the wind. As they near a beach, their speed decreases as the water gradually becomes shallower. The diagram shows water waves out at sea. Complete the diagram to show the wavefronts as they near the beach.

B e a c h

W a v e f r o n t

W i n dd i r e c t i o n

(3)

The diagram below shows waves heading directly towards an enclosed bay. Assume the depth of water in the bay is constant. Complete the diagram to show what happens to the wavefronts in the bay.

W a v ed i r e c t i o n

E n c l o s e d b a y

(2)

In ‘The Last Word’ section of the New Scientist a reader has asked the following question: “Why do waves travel towards the shore no matter which way the wind blows?”Suggest an explanation.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(1)

(Total 8 marks)

136. Resistivity measurements under the sea have been used to find new sources of fresh water.

Two probes are towed along the seabed behind a small boat.

S u r f a c e o f s e aB o a t

S e a b e d

P r o b e s

Taking measurements using these probes, resistivity can be calculated at various depths below the seabed.

What measurements are needed to calculate resistivity?

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

The diagram below displays the resistivities measured in a survey.

0

1 0

2 0

1 . 8 2 . 0 2 . 2 2 . 4 2 . 6D i s t a n c e t o s h o r e / k m

Dep

th b

elow

sea

bed

/ m

2 . 54 . 0

6 . 21 0

R e s i s t i v i t yv a l u e s / mΩ

Line A below has been plotted using some of this data. It shows how resistivity ρ varies with depth below the seabed 2.0 km from the shore.

/ Ω m

2 0

1 5

1 0

5

0

– 50 5 1 0 1 5 2 0 2 5 3 0

D e p t h / m

A

Make measurements from this graph to determine the equation of line A.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

Use the survey results to add another line to show how resistivity varies with depth 2.4 kmfrom the shore.

(3)

The resistivity gradient (the variation of resistivity with depth) is greater in areas where there is fresh water below the seabed. Suggest the best distance from the shore to drill for fresh water.

...............................................................................................................................................(1)

(Total 10 marks)

137. Ultrasound is used to produce pictures of the fetus in the womb. One of these appears below.

What is ultrasound?

...............................................................................................................................................

...............................................................................................................................................(1)

Explain how ultrasound can be used to build up a picture of a fetus within the womb.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

How can reflected ultrasound provide information about a beating heart?

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 6 marks)

138. An advertisement for an active noise cancellation headset for aircraft pilots contains the following information:

Requires 9 V batteryActive noise attenuation over 20 – 800 Hz

Rubberized foam earcups

Explain the physics principles in each statement of this advertisement. You could start by saying why a battery is required and go on to explain how the noise is attenuated.

(Allow one lined page)(6)

A student asks the following question: “If sound is being introduced to cancel out the noise, then where does the energy go?”

What is the explanation?

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 8 marks)

139. Four 10 Ω resistors are connected as shown in the diagram.

1 0 Ω

1 0 Ω

1 0 Ω

1 0 Ω

Calculate the total resistance of the combination.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

Total resistance = .................................(3)

Comment on your answer and suggest why such a combination of resistors might be used.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................(2)

(Total 5 marks)

140. Use the axes to draw the current-voltage characteristic of a diode.

I

V

(3)

Use the axes to draw the current-voltage characteristic of a filament lamp.

I

V

(3)(Total 6 marks)

141. A cell of negligible internal resistance is connected in series with a microammeter of negligible resistance and two resistors of value 15 kΩ and 25 kΩ. The current is 150 μA.Draw a circuit diagram of the arrangement.

(1)

Show that the e.m.f. of the cell is 6.0 V.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................(2)

A voltmeter is now connected in parallel with the 25 kΩ resistor. Draw a diagram of the new circuit.

(1)

When the voltmeter is connected the reading on the microammeter increases to 170 μA.Calculate the resistance of the voltmeter.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

Resistance = .........................................(3)

(Total 7 marks)

142. Lord Kelvin discovered that the electrical resistance of iron wire changed when the wire was stretched or compressed. This is the principle on which a resistance strain gauge is based. Such a gauge consists of a length of very fine iron wire cemented between two very thin sheets of paper.

G a u g e l e n g t h = 2 . 4 × 1 0 m– 2

S t r a i n g a u g e

T h i np a p e r

F i n e i r o nw i r e

The cross-sectional area of the wire is 1.1 × 10–7 m2 and the gauge length as shown in the

diagram is 2.4 × 10–2 m. The resistivity of iron is 9.9 × 10–8 Ω m. Calculate the resistance of the strain gauge.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

Resistance of strain gauge = ..................................(4)

When this gauge is stretched its length is increased by 0.1% but its cross-sectional area remains the same. What is the change in the resistance of the gauge?

................................................................................................................................................

................................................................................................................................................

Change in resistance = ...........................................(2)

Explain the effect that stretching the wire will have on the drift velocity of electrons in the wire. Assume that the other physical dimensions of the wire remain unchanged and that there is a constant potential difference across the wire.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................(3)

(Total 9 marks)

143. The diagram shows an experiment with sound waves.

S i g n a lg e n e r a t o r

L o u d s p e a k e r

M i c r o p h o n e

O s c i l l o s c o p e

B e n c h

x

A loudspeaker connected to a signal generator is mounted, pointing downwards, above a horizontal bench. The sound is detected by a microphone connected to an oscilloscope. The height of the trace on the oscilloscope is proportional to the amplitude of the sound waves at the microphone.

When the vertical distance x between the microphone and the bench is varied, the amplitude of the sound waves is found to vary as shown on the graph.

1 6

1 2

8

4

00 4 8 1 2 1 6 2 0

x / c m

A m p l i t u d e / a r b i t r a r y u n i t s

Explain why the amplitude of the sound has a number of maxima and minima.You may be awarded a mark for the clarity of your answer.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................(5)

The frequency of the sound waves is 3.20 kHz. Use this, together with information from the graph, to determine a value for the speed of sound in air.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

Speed of sound = ............................................(4)

The contrast between the maxima and minima becomes less pronounced as the microphone is raised further from the surface of the bench. Suggest an explanation for this.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................(2)

(Total 11 marks)

144. The diagram shows some of the energy levels of a mercury atom.

0 I o n i s a t i o n

– 1 . 6

– 5 . 5

– 1 0 . 4

E n e r g y / e V

Calculate the ionisation energy in joules for an electron in the –10.4 eV level.

................................................................................................................................................

................................................................................................................................................

Ionisation energy = ...................................... J(2)

A proton of kinetic energy 9.2 eV collides with a mercury atom. As a result, an electron in the atom moves from the –10.4 eV level to the –1.6 eV level. What is the kinetic energy in eV of the proton after the collision?

................................................................................................................................................

................................................................................................................................................

Kinetic energy = .............................................(1)

A transition between which two energy levels in the mercury atom will give rise to an emission line of wavelength 320 nm?

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................(3)

(Total 6 marks)

145. The diagram shows apparatus for an experiment on the photoelectric effect.

R a d i a t i o n

C A

V

n A

Monochromatic radiation strikes the cathode C and photoelectrons are emitted towards the anode A. When a potential difference V is applied, a current I is measured on the very sensitive ammeter. Data can also be obtained with the polarity of the supply reversed. Using this apparatus, graph (a) below was obtained. After making a change to the incident radiation, graph (b) was obtained.

( a )

( b )

I

V00

What can be deduced about the incident radiations from

(i) the fact that both curves start from the same point on the negative V axis,

....................................................................................................................................

....................................................................................................................................

(ii) the higher final value of the current I in (a) compared to (b)?

....................................................................................................................................

....................................................................................................................................(2)

The cathode is now replaced by one made from a metal with a higher work function.On the same axes, sketch a graph labelled (c) showing what would be observed if the original radiation were used.

(1)

The work function of the metal of the cathode is 7.2 × 10–19 J. Calculate the maximum speed of the photoelectrons emitted when the incident radiation has a frequency of 7.9 ×

1015 Hz.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

Maximum speed = ..........................................(4)

(Total 7 marks)

146. Ultraviolet radiation from the sun can cause sunburn. However, not all ultraviolet wavelengths cause sunburn to the same extent.

What is meant by wavelength?

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Explain why ultraviolet radiation is more likely to cause sunburn than visible light, which has a longer wavelength.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Scientists put a lot of effort into developing suncreams which absorb the damaging wavelengths of ultraviolet radiation. Suggest what might be happening to the atoms within the suncream when they absorb ultraviolet photons.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 6 marks)

147. In testing railway lines for faults, an ultrasonic probe is placed on a rail.

P r o b eT oo s c i l l o s c o p e

U l t r a s o u n d W a v e f r o n t s

R a i l

Every 1.0 × 10–1 s, the probe emits a short pulse of ultrasound. The speed of ultrasound in steel

is 5100 m s–1. The probe, which also acts as a receiver, is connected to an oscilloscope which displays the trace shown below.

T i m e b a s e 1 . 0 × 1 0

– 5s c m– 1

1 c m

How can you tell that the left peak represents the emitted pulse?

...............................................................................................................................................

...............................................................................................................................................(1)

Calculate the depth of the rail using a measurement from the oscilloscope trace.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

The probe is now moved to another position on the rail where there is a crack one third of the way down from the top.

R a i l C r a c k

Describe how the oscilloscope trace will change.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

The ultrasound diffracts round the crack because the crack behaves like an obstacle.Draw wavefronts on the above diagram to show what this means.

(2)(Total 8 marks)

148. A 40 mm strip of light-sensitive material is used in a camera with automatic focus.

4 0 m m

L i g h t - s e n s i t i v em a t e r i a l

The lens is moved automatically until light is sharply focused onto a very short length of this strip. The graph shows how the resistance R of the total length of the strip varies with light intensity.

4

3

2

1

00 2 4 6 8 1 0

I n t e n s i t y / a r b i t r a r y u n i t s

R / k Ω

Calculate the resistance per mm of the strip when it is in complete darkness.

...............................................................................................................................................

...............................................................................................................................................(2)

Bright light of intensity 10 units is focused on an 8 mm length of the strip.

Show that the resistance of the 8 mm length is 40 Ω .

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

The remainder of the strip is in the dark.

Calculate its resistance.

...............................................................................................................................................

...............................................................................................................................................(1)

A cell of e.m.f. 1.2 V and negligible internal resistance is connected across the ends of the strip. Calculate

(i) the current in the strip,

.....................................................................................................................................

.....................................................................................................................................

(ii) the p.d. across the 8 mm length.

.....................................................................................................................................

.....................................................................................................................................(4)

Explain why this current decreases as the bright light is more sharply focused onto a smaller length of the strip.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 11 marks)

149. A student writes up an experiment on the photoelectric effect.

We scratched the surface of a magnesium strip and set it up in front of a UV light. When we switched on the UV light, the ammeter showed a current but, when we put a sheet of glass in between the light and the magnesium, the current stopped. There was also no current when visible light shone on the magnesium.

The student included this circuit diagram:

A

S e n s i t i v ea m m e t e r

M a g n e s i u ms t r i p

C o p p e r w i r e

U V

However, the experiment would not work with this circuit. State the error in the circuit diagram, giving your reasoning.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

The student gives the following wrong explanation:

This shows that UV light is made up of particles called electrons. Visible light is just transverse waves, since there was no current when this was used.

Finish the first sentence correctly:

This shows that UV ...........................................................................................................

...............................................................................................................................................(1)

The student has not understood the difference between UV and visible light. How are UV and visible light.

(i) different ......................................................................................................................

.....................................................................................................................................

(ii) similar? .......................................................................................................................

.....................................................................................................................................(2)

Low-intensity UV produces a current in this experiment but even bright visible light does not. Explain why this is.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

Suggest why the current stopped when the sheet of glass was used.

...............................................................................................................................................

...............................................................................................................................................(1)

(Total 9 marks)

150. Explain the term total internal reflection.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Below is an illustration of a pedobarograph and an image of a foot. This is a medical instrument used for measuring foot pressure when investigating problems with feet.

L i g h t

C a m e r a

O b s e r v e d i m a g eo f f o o t

M i r r o r

F o o t

P l a s t i cf i l m

G l a s sp l a t e

Calculate the critical angle for total internal reflection to occur at the glass-air interface. The refractive index of the glass is 1.5.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Light rays are totally internally reflected within the glass plate except at the points where the feet press the plastic film against the glass.

Complete the path of the ray in the diagram below.

F o o t

P l a s t i c

G l a s s

A i r

L i g h t r a y

A i r g a p

n o t t os c a l e

(2)

Where the pressure from the foot forces the plastic in contact with the glass the light passes through the plastic and is then scattered from the foot.

Complete the path of ray A on the diagram below. The refractive index of the plastic used is approximately the same as glass.

A i r g a p

S c a t t e r e d r a y sf r o m f o o t

F o o t

P l a s t i c

G l a s s

A i r

L i g h tr a y

n o t t os c a l e

A

(3)

With reference to your ray diagrams above, explain why there are bright and dark patches on the image produced by the camera.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 11 marks)

151. Explain what is meant by the term polarisation when referring to light.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Sugar is produced from plants such as sugar cane. The stems are crushed and the juice extracted. The concentration of sugar in the juice is used to value the crop.

The concentration can be determined using polarised light.

Explain how to measure the angle of rotation of polarised light when it passes through a sugar solution.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(4)

A student has carried out this experiment and obtains three results. He has plotted them on the graph below. He takes three more results and tabulates them.

Angle of rotation/degrees Concentration of solution/kg per litre

17 0.25

33 0.50

50 0.75

Add these results to the graph.(3)

0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0

6 0

5 0

4 0

3 0

2 0

1 0

0

A n g l e / d e g r e e

C o n c e n t r a t i o n o f s o l u t i o n / k g p e r l i t r e

Use your graph to determine the concentration of an unknown sample which gives a rotation of 38°.

Concentration: .................................................................................................... kg per litre(1)

(Total 10 marks)

152. A firework is stuck into the ground 400 m from an observer.

The observer sees the flash of the firework, then feels a vibration through the ground and finally hears the bang. Explain these observations.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(Total 2 marks)

153. A student is provided with two filament lamps A and B. Each is rated 12 V 60 W, but lamp A has a carbon filament and lamp B a tungsten filament.

Calculate the resistance of each filament lamp under normal operating conditions.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Resistance = ..............................................(3)

The graph shows the relationship between the current I and the potential difference V for the two filament lamps.

6

5

4

3

2

1

00 2 4 6 8 1 0 1 2 V / V

I / A

L a m p B

L a m p A

Describe how the resistances of lamp A and lamp B vary with current.

Lamp A: ...............................................................................................................................

...............................................................................................................................................

Lamp B: ................................................................................................................................

...............................................................................................................................................(2)

The diagram shows the two filament lamps connected in series across a battery of e.m.f 12 V and negligible internal resistance. Both filaments glow dimly, but the hlank filament of lamp A is the brighter.

L a m p A L a m p B

1 2 V

Why does each filament glow only dimly?

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(1)

Suggest why the filament of lamp A is the brighter.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 8 marks)

154. A 500 W electric toaster operates from the 230 V mains. Calculate the current in the heating element of the toaster.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Current = ........................................................(3)

The heating element of the toaster is made of much thinner wire than the wire in its supply cable. In which of these two wires do the electrons have the greater drift velocity?

...............................................................................................................................................(1)

Explain your answer. You may be awarded a mark for the clarity of your answer.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(4)

(Total 8 marks)

155. The diagram shows a type of resistor commonly used in electronic circuits.

It consists of a thin film of carbon wrapped around a cylindrical insulator. The diagram below (not to scale) shows a typical film of carbon, resistivity ρ , before it is wrapped round the insulator.

C a r b o n f i l m

II

t

l

w

Show that the resistance R of the carbon film is given by

wt

lR

ρ=

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

This film has length l = 8.0 mm, width w = 3.0 mm and thickness t = 0.0010 mm

(i.e. t = 1.0 × 10–6 m). If the resistivity of carbon is 6.0 × 10–5Ω m, calculate the resistance of the carbon film.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Resistance = ..................................................(3)

Show that the resistance of a square piece of carbon film of uniform thickness is independent of the length of the sides of the square.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 7 marks)

156. Define the term e.m.f. of a cell.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

A student wants to use a graphical method to determine the internal resistance r of a cell of

known e.m.f. ε .

Complete the diagram below showing how the cell should be connected in a circuit to allow the student to do this.

rε

(2)

Sketch the graph the student should plot and state how she could determine r from the graph.

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 6 marks)

157. Each of the diagrams below shows a series of wavefronts, one wavelength apart, approaching a gap between two barriers in a ripple tank.

What is a wavefront?

...............................................................................................................................................

...............................................................................................................................................(1)

Add further wavefronts to each diagram to show what happens as the waves pass through each gap.

(3)

The station BBC Radio 4 broadcasts both on the Long Wave band at 198 kHz and on VHF at approximately 94 MHz. In mountainous parts of the country, reception is better on Long Wave than on VHF. Suggest why.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 6 marks)

158. An electric eel has the ability to generate an e.m.f. and hence drive current through the surrounding water. Its body can be modelled as a battery containing a large number of cells. Such a battery has 20 parallel rows, each with 6000 cells connected in series. Each cell has an e.m.f of 40 × 10–3 V and an internal resistance of 0.70 Ω .

6 0 0 0 c e l l s+ –

H e a d T a i l

2 0

r o w s

When the eel is in the water, current can pass from its head to the tip of its tail through the water, stunning any other fish near it.

Calculate the total e.m.f. of one row of 6000 cells in series.

...............................................................................................................................................

...............................................................................................................................................

e.m.f. = ..........................................(2)

Calculate the total internal resistance of this row of cells.

...............................................................................................................................................

...............................................................................................................................................

Internal resistance = ..........................(1)

Calculate the current which passes through the seawater if the eel is able to activate just one of its rows of 6000 cells. (Assume the resistance of seawater is zero.)

...............................................................................................................................................

...............................................................................................................................................

Current = .....................................(2)

In fact, all 20 rows of cells drive current at the same time. Calculate the total current which passes through the seawater.

...............................................................................................................................................

...............................................................................................................................................

Current = ...................................(1)

If you could connect a voltmeter across the eel from head to tall when it is delivering the total current, its reading, would not equal the total e.m.f. Explain why.

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...............................................................................................................................................

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...............................................................................................................................................(2)

State the voltmeter reading while the eel is delivering current through the seawater.

Voltmeter reading = ....................................(1)

(Total 9 marks)

159. A student has heard that the bright colours that he has noticed in soap bubbles are caused by superposition. To investigate this he sets up an experiment in a darkened laboratory. He bends a piece of wire into a rectangular shape, and mixes up a beaker of soapy water. He puts a sodium lamp (emitting bright yellow light) at one end of the bench. Then he dips the rectangle of wire into the soapy water so that a soap film forms, and puts the wire rectangle with its soap film into a clamp so that it stands vertically in front of the lamp – see Figure 1.

W i r e r e c t a n g l eS o a pf i l m

L a m p

F i g u r e 1 F i g u r e 2

A i r A i rS o a pf i l m

X

Y

Figure 2 represents two possible paths for light to pass through the film from the lamp to the student. One path (labelled X) shows light passing straight through the film. The light following path Y is reflected twice, once at each side of the film, during its passage from the lamp to the student.

The thickness of the film in Figure 2 is 1.11 × 10–7 m. How much further does light following path Y travel compared with light following, path X?

...............................................................................................................................................

...............................................................................................................................................

Path difference = .............................(1)

The wavelength of the yellow sodium light in the soap film is 4.44 × 10–7 m. Explain why the part of the film shown in Figure 2 appears dark to the student.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

In fact the thickness of the film increases from the top of the film to the bottom.Suggest a reason for this.

...............................................................................................................................................

...............................................................................................................................................(1)

At another place the thickness of the film is 2.22 × 10–7 m. Explain whether this part of the film appears bright or dark.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

As the student looks at the whole film, from top to bottom, he sees alternate bright and dark horizontal stripes. Explain this effect.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

As the student watches, the whole pattern of bright and dark stripes gradually moves downwards. Explain this effect.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Add to Figure 2 another possible path for light travelling from the lamp to the student.(1)

(Total 11 marks)

160. Travellers in hot places often think that they see water in the distance, when there is nothing but land there. This effect is called a mirage. The air near the ground is very hot, and light reflects off the top of this layer of hot air.

The diagram below shows how you could demonstrate the effect in a laboratory.

G l a s s b l o c kA i r

On the diagram draw appropriate normals and mark

(i) an angle of incidence, labelled I,

(ii) an angle of refraction, labelled R, and

(iii) an angle labelled G which you know is greater than the critical angle.(3)

What does the way light refracts tell you about the velocity of light in glass compared with the velocity in air?

...............................................................................................................................................

...............................................................................................................................................(1)

How does the velocity of light in the layer of hot air near the around compare with the velocity in the cooler air higher up?

...............................................................................................................................................

...............................................................................................................................................(1)

Which property of the air has been changed by the temperature difference, producing this change in velocity?

...............................................................................................................................................

...............................................................................................................................................(1)

(Total 6 marks)

161. The table gives the resistivities of five different materials:

Material Resistivity/ Ω m

Copper 1.8 × 10–8

Iron 1.2 × 10–7

Carbon 1.4 × 10–5

Silicon 2.3 × 103

Glass 1.0 × 1012

A student needs to make a 0.12 Ω resistor. She has some copper wire of diameter 0.80 mm.

(i) Show that the cross-sectional area of the wire is about 5 × 10–7 m2

.....................................................................................................................................

.....................................................................................................................................(2)

(ii) Calculate the length of wire she needs for the 0.12 Ω resistor.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

What would be the advantage of making the resistor from iron wire of the same diameter?

.....................................................................................................................................

.....................................................................................................................................(1)

(Total 6 marks)

162. Many modem cameras have built-in exposure meters. These can detect the intensity of light falling, on to the film and automatically adjust how long the film is exposed to the light. One type of device that can be used is the photocell below.

L i g h tr a y s

A n o d e ( c o l l e c t s e l e c t r o n s )

E l e c t r o n s

S e c t i o n t h r o u g hc u r v e d c a t h o d e( p r o d u c e s e l e c t r o n s )

Photons hitting the cathode cause photoelectrons to be released from the surface of the cathode if it is made from a material with a suitable work function.

Describe how an electron escapes from the surface of the cathode. Include the terms in bold from the passage above.

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

Potassium has a work function of 2.90 × 10–19 J. Calculate the lowest frequency of radiation that will produce photoelectrons from a potassium surface.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

The exposure meter will produce the best results if it responds to light over most of the visible spectrum. This has a range of wavelengths from 4.0 × 10–7 m to 7.0 × 10–7 m.

Explain with the aid of an appropriate calculation whether potassium is a suitable material for use in an exposure meter.

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................(2)

A potassium cathode is exposed to visible light, with a complete range of wavelengths. Show that the maximum kinetic energy of an emitted photoelectron is about 2 × 10–19 J.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................(3)

Give one reason why some photoelectrons will be emitted with less than this kinetic energy.

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................(1)

(Total 12 marks)

163. State the unit of the base quantity current.

...............................................................................................................................................(1)

Determine the base units of potential difference.

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................(3)

(Total 4 marks)

164. An electric room heater consists of three heating elements connected in parallel across a power supply.

P o w e rs u p p l y

X Y

Each element is made from a metal wire of resistivity 5.5 × 10–5 Ω m at room temperature. The

wire has a cross-sectional area 8.0 × 10–7 m2 and length 0.65 m.

The heater is controlled by two switches, X and Y.

Show that the resistance of one heating element at room temperature is approximately 45 Ω .

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

Calculate the total resistance of the heater for the following combinations of switches at the moment the switches are closed.

Switch X Switch Y Resistance of heater / Ω

Open Closed

Closed Open

Closed Closed

(3)

Calculate the maximum power output from the heater immediately it is connected to a 230 V supply.

...............................................................................................................................................

...............................................................................................................................................

Maximum power = .................................................(2)

After being connected to the supply for a few minutes the power output falls to a lower steady value. Explain why this happens.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 10 marks)

165. A thick wire is connected in series with a thin wire of the same material and a battery.

In which wire do the electrons have the greater drift velocity? Explain your answer.

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................(3)

A battery is connected across a large resistor and a small resistor is connected in parallel. The currents through the resistors are different.

Which resistor has the higher dissipation of power? Explain your answer.

...............................................................................................................................................

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...............................................................................................................................................(3)

(Total 6 marks)

166. A student investigates how the current in a resistor varies as the potential difference across the resistor is varied. Draw a suitable circuit diagram for the investigation.

(3)

The graphs show the variation of current with potential difference for a filament lamp and for an ohmic resistor.

0 . 7

0 . 6

0 . 5

0 . 4

0 . 3

0 . 2

0 . 1

00 1 2 3 4 5 6 7 8 9 1 0

C u r r e n t / A

P o t e n t i a l d i f f e r e n c e / V

Label one graph lamp and the other graph resistor.(1)

The lamp and resistor are connected in series as shown. There is a current of 0.50 A.

0 . 5 0 A

Use the graph to find the total potential difference across the combination.

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................

Potential difference = .............................................(2)

What is the resistance of the lamp under these conditions?

...............................................................................................................................................

...............................................................................................................................................

Resistance = .......................................(2)

(Total 8 marks)

167. Radio waves and sound waves are sometimes confused by the general public.Complete the table to give three ways in which they differ.

Radio waves Sound waves

(3)

It is proposed to place a solar power station in orbit around the Earth. The solar power station will convert sunlight to microwave energy. Microwave collectors on Earth will convert the microwaves into electricity.

M i c r o w a v e sM i c r o w a v ec o l l e c t o r

S u r f a c e o f E a r t h

The solar power station orbits the Earth at a constant distance from the surface of 36 000 km.The total area of the collectors is equivalent to a rectangle with dimensions of 120 m by 250 m.

The collectors are used to generate 600 kW of power. Calculate the intensity of the microwaves at the collectors. State any assumption that you make.

...............................................................................................................................................

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Intensity = .......................................................(3)

Calculate the total power which the orbiting station would have to emit if it transmitted microwaves equally in all directions. State any assumption that you make.

...............................................................................................................................................

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...............................................................................................................................................

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Power = ...........................................................(3)

Suggest a more efficient method of transmitting the microwave energy to the collectors on Earth.

...............................................................................................................................................(1)

(Total 10 marks)

168. The following diagram shows the lowest four energy levels of atomic hydrogen.

– 0 . 8 5 e V

– 1 . 5 e V

– 3 . 4 e V

– 1 3 . 6 e V

Calculate the ionisation energy in joules for atomic hydrogen.

...............................................................................................................................................

...............................................................................................................................................

Ionisation energy = ........................................ J(2)

On the diagram above draw

(i) a transition marked with an R which shows a photon released with the longest wavelength,

(ii) a transition marked with an A which shows a photon absorbed with the shortest wavelength.

(2)

Describe how you would produce and observe the emission spectrum of hydrogen in the laboratory.

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................

What would such a spectrum look like?

...............................................................................................................................................

...............................................................................................................................................(3)

The 211 mm line of atomic hydrogen is often used in studying stars or galaxies.To which region of the electromagnetic spectrum does this line belong?

...............................................................................................................................................(1)

A galaxy is observed with the 211 mm line shifted to a wavelength of 203 mm.Calculate the speed of this galaxy.

...............................................................................................................................................

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Speed of galaxy = ..........................................

What else can be deduced about the motion of this galaxy?

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...............................................................................................................................................(4)

(Total 12 marks)

169. The photoelectric effect supports a particle theory of light but not a wave theory of light.

State two features of the photoelectric effect which support the particle theory of light but which do not support the wave theory of light. For each feature explain why it supports particle theory and not wave theory.

Feature 1: ..............................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Explanation: .........................................................................................................................

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...............................................................................................................................................

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Feature 2: .............................................................................................................................

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...............................................................................................................................................

Explanation: .........................................................................................................................

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...............................................................................................................................................(Total 5 marks)

170. Describe with the aid of a diagram how you could produce stationary waves on a string.

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...............................................................................................................................................(3)

Explain how you could use a stationary wave to determine the speed of travelling waves on the string. You may be awarded a mark for the clarity of your answer.

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(Total 7 marks)

171. Sometimes shiny colours maybe seen on the surface of cold meats, with different colours appearing at different parts of the surface. It has been suggested that this is caused because the fat and water on the surface of the meat separate into two layers. The colours are caused by superposition of light reflected from the upper and lower surfaces of the fat layer.

F a t

W a t e r

M e a t

What is meant by superposition?

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

At one point on the surface where light strikes the top of the fat layer at right angles, the path difference between reflecting from the top and bottom surfaces of the fat layer is 8 × 10–7 m.

Calculate the thickness of the fat layer here.

...............................................................................................................................................

...............................................................................................................................................

Thickness = ...............................................................(1)

In fat, green light has wavelengths between about 3.7 ×10–7 m and 4.1 × 10–7 m.

Explain why some green light will undergo constructive superposition at this place on the meat.

...............................................................................................................................................

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...............................................................................................................................................(2)

The whole visible spectrum has wavelengths between about 3.0 × 10–7 m and 5.2 × 10–7 m in fat.

Explain what happens to wavelengths other than green light at this place in the meat.

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...............................................................................................................................................(2)

Explain why shiny colours other than green may be seen at different places on the surface of the meat.

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(Total 9 marks)

172. A student read that a lemon could be used to power a clock. He made an electrical cell using a lemon and placed it in this circuit. The table shows the readings he obtained. The first reading was taken with switch S open. To obtain the others he closed S and varied the resistance R.

A

R

S

V

R e a d i n g

123456

C u r r e n t / n A V o l t a g e / m V

1 1 08 37 45 73 52 0

09 0

1 5 02 1 03 1 03 5 0

The prefix n, as in nA, means “× 10–9”.

What does the prefix m, as in mV, mean?

...............................................................................................................................................(1)

Calculate the value of R for reading 3.

...............................................................................................................................................

...............................................................................................................................................

Resistance = .............................................................(2)

Calculate the power being supplied by the cell to resistance R for reading 4.

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Power = ....................................................................(2)

The student plotted his results on a graph like the one shown. Points for readings 4, 5 and 6 have already been plotted. Complete the graph.

×

×

×

1 0 0

5 0

00 1 0 0 2 0 0 3 0 0 4 0 0 I / n A

V / m V

Predict the current that would flow from the cell if it were short-circuited, that is, if R were reduced to zero.

...............................................................................................................................................

...............................................................................................................................................(1)

State what the experiment suggests for the value of the e.m.f. of the cell.

...............................................................................................................................................(1)

Explain why the voltage across the cell falls as R is reduced.

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...............................................................................................................................................(2)

(Total 12 marks)

173. The photograph sequence shows a ripple spreading out over the surface of the sun, following an event similar to an earthquake somewhere within it. The interval between each successive frame is 10 minutes. A distance scale is marked beside each frame.

Measure the diameter of the dark ring of the ripple in frames 1 and 2 in mm.

Diameter of dark ring in frame 1 = ...................... mm

Diameter of dark ring in frame 2 = ...................... mm(1)

Show that in the time interval between frames 1 and 2, the ripple travels about25 ×106 m.

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................(2)

Hence calculate a speed in m s–1 for the ripple from frame 1 to frame 2.

...............................................................................................................................................

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Speed = ........................................................ m s–1

(3)

How could a physicist check whether the speed of the ripple was constant?

...............................................................................................................................................

...............................................................................................................................................(1)

The diagram shows a cross-section of part of the ripple for the first photograph.

D i s p l a c e m e n t o fS u n ' s s u r f a c e

D i s t a n c e f r o me p i c e n t r e

0

On the diagram above, mark and label the wavelength and amplitude.(2)

The wavelength is 1.4 × 107 m.

Calculate the frequency of the waves.

...............................................................................................................................................

...............................................................................................................................................

Frequency = ..............................................................(2)

(Total 11 marks)

174. There are concerns among fishermen that dwindling fish stocks in the world’s oceans are result a of modern fishing, techniques. Fishing trawlers can detect shoals of fish using ultrasound.

Describe the movement of water molecules when an ultrasound wave passes.

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...............................................................................................................................................(2)

Ultrasound pulses can be transmitted into the sea and the reflected waves can be detected and used to find the position of a shoal of fish.

Explain why pulses of ultrasound are used.

...............................................................................................................................................

...............................................................................................................................................(1)

A shoal of fish is at a depth of 300 m. Calculate the time interval between transmitting the pulse and receiving its echo.

(The speed of ultrasound in water = 1500 m s–1.)

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Time interval = .............................................................(2)

A continuous ultrasound signal can be used to determine the speed of the shoal of fish.

Name the effect used in this method.

...............................................................................................................................................

Briefly explain the physics principles of this effect.

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(Total 8 marks)

175. A physics teacher was driving to work when she heard the following report on the radio.

“Scientists have been researching a method of judging people’sopinions of politicians. They have found that the more stronglyopposed people are to a politician’s views, the more their handssweat. This can be detected using a resistivity meter which has twoprobes resting on the palm of the hand.”

Write down an equation to define resistivity, stating what each symbol represents.

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...............................................................................................................................................(3)

Why should the resistivity meter strictly be called a resistance meter?

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...............................................................................................................................................(2)

The teacher decided to see if this idea would work. She used a multimeter to measure the resistance across her palm as shown in the picture below.

She obtained the following readings with the probes 2 cm apart:

Radio Topic Teacher’s feelingsApproximate

resistance/MΩ

Comedy Very relaxed 3

Music Relaxed 2

Politics Annoyed 1

Do these results support the claims of the reporter? Give your reasoning.

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(Total 8 marks)

176. The table gives four word equations. Complete the table with the quantity defined by each word equation.

Word Equation Quantity Defined

Voltage ÷ Current

Voltage × Current

Charge ÷ Time

Work Done ÷ Charge

(Total 4 marks)

177. A lightning stroke passes between a cloud and a lightning conductor attached to a tall building.

A very large current of 20 000 A passes for 4.0 × 10–4 s.

C l o u d

L i g h t n i n g

G r o u n d

T a l lB u i l d i n g

C o n d u c t o r5 0 m h i g h

Calculate the charge flowing to the ground in this time.

...............................................................................................................................................

...............................................................................................................................................

Charge = ..................................................................(2)

The lightning conductor is 50 m high and has a cross-sectional area of 1.0 × 10–3 m2.

It is made from copper which has a resistivity of 1.7 × 10–8 Ω m.

Calculate the resistance of the lightning conductor.

...............................................................................................................................................

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Resistance = .................................................(3)

Hence calculate the potential difference between the top and bottom of the current-carrying lightning conductor.

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Potential difference = .......................................................(2)

If lightning strikes a tree such that there is the same current through it as there was through the conductor, then a much larger potential difference exists between the top and bottom of the tree. Explain why this is so.

...............................................................................................................................................

...............................................................................................................................................(1)

(Total 8 marks)

178. A student has four identical resistors each of resistance 10 Ω . She connects them to form the different networks shown below.

Calculate the equivalent total resistance of each network.

F i r s t n e t w o r k

S e c o n d n e t w o r k

T h i r d n e t w o r k

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

T o t a l r e s i s t a n c e = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ω

T o t a l r e s i s t a n c e = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ω

T o t a l r e s i s t a n c e = . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ω(3)

She then connects a battery across the second network and adds meters to make the circuit shown below. A current of 50 mA is drawn from the battery.

A

V

1 0 Ω

1 0 Ω

1 0 Ω

1 0 Ω

5 0 m A

2

V 1

Determine the reading on each of the three meters.

Reading on ammeter A:

...............................................................................................................................................

Ammeter reading = .......................................................... mA

Reading on voltmeter V1:

...............................................................................................................................................

Voltmeter reading = ........................................................... V

Reading on voltmeter V2:

...............................................................................................................................................

...............................................................................................................................................

Voltmeter reading = ........................................................... V(5)

(Total 8 marks)

179. Two resistors of resistance 2.0 MΩ and 4.0 Ω are connected in series across a supply voltage of 6.0 V. Together they form a simple potential divider circuit.

State the potential difference across each resistor.

+ 6 . 0 V

0 V

2 . 0 M Ω

4 . 0 Ω

P.d. across the 2.0 MΩ resistor = .........................................................................................

P.d. across the 4.0 Ω resistor = ............................................................................................(2)

A second potential divider circuit uses a resistor and a diode connected in series with the same supply. Calculate the potential difference across each component when the resistance of the resistor and diode are 45 Ω and 5.0 Ω respectively.

+ 6 . 0 V

0 V

4 5 Ω

5 . 0 Ω

...............................................................................................................................................

P.d. across the 45 Ω resistor = ............................................

...............................................................................................................................................

P.d. across the diode = ........................................................(2)

In this circuit the diode is in forward bias. Use the axes below to sketch a graph of current I against potential difference V for a diode in forward bias.

I / A

0 V / V(1)

(Total 5 marks)

180. The diagram shows the shape of a wave on a stretched rope at one instant of time. The wave is travelling to the right.

0 . 0 0 0 . 2 0 0 . 4 0 0 . 6 0 0 . 8 0 1 . 0 0 1 . 2 0 1 . 4 0

D i s t a n c e / m

D i r e c t i o n o f t r a v e l o f w a v e

C

A

Determine the wavelength of the wave.

Wavelength = .........................................................

Mark on the diagram a point on the rope whose motion is exactly out of phase with the motion at point A. Label this point X.

Mark on the diagram a point on the rope which is at rest at the instant shown. Label thispoint Y.

Draw an arrow on the diagram at point C to show the direction in which the rope at C is moving at the instant shown.

(4)

The wave speed is 3.2 m s–1. After how long will the rope next appear exactly the same as in the diagram above?

...............................................................................................................................................

...............................................................................................................................................

Time = .................................................................(2)

(Total 6 marks)

181. Describe how you would demonstrate experimentally that electromagnetic waves can be polarised, using either light or microwaves. Include a diagram of the apparatus you would use.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(4)

What does the experiment tell you about the nature of electromagnetic waves?

...............................................................................................................................................

...............................................................................................................................................(1)

(Total 5 marks)

182. The graph shows how the maximum kinetic energy T of photoelectrons emitted from the surface of sodium metal varies with the frequency f of the incident electromagnetic radiation.

4 . 0

2 . 0

0 . 0

– 2 . 0

– 4 . 0

2 . 0 4 . 0 6 . 0 8 . 0 1 0 . 0 1 2 . 0

f / 1 0 H z

T / 1 0 J– 1 9

1 4

Use the graph to find a value for the Planck constant.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Planck constant = ........................................................(3)

Use the graph to find the work function φ of sodium metal.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Work function = ........................................................(2)

(Total 5 marks)

183. Sam bought a new set of Christmas tree lights. The box stated, “40 lamps, 6.0 V0.78 W each”.

Calculate the working current of each lamp.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Current = ...............................................................(2)

Calculate the working resistance of each lamp.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Resistance = ...............................................................(2)

Explain how this set of lights can operate normally from a mains supply of 240 V.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Sam thought the lamps at the top of the Christmas tree would light more faintly than the others because the current would have to flow further through the wires to reach them. Explain why all the lamps are lit equally brightly.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(1)

Sam decides to check the lamps before connecting them to the mains. He measures the resistance of each lamp with an ohmmeter. This does not make the lamp light up. He discovers that the measured resistance is not the same as the working resistance.

State whether the measured resistance is higher or lower than the working resistance.

...............................................................................................................................................

Explain this observation.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

(3)(Total 10 marks)

184. A rechargeable battery for an electronic game is marked with the following information:

Output 3.0 V, capacity 1.5 amp hours

Explain why “amp hours” is a unit of charge.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Show that the charge equivalent to 1.5 amp hours is about 5000 C.

...............................................................................................................................................

...............................................................................................................................................(1)

Calculate the energy stored in the battery when it is fully charged, assuming the output voltage remains constant at 3.0 V.

...............................................................................................................................................

...............................................................................................................................................

Energy stored = ...............................................................(2)

To recharge the battery a supply voltage of 3.1 V is used with a current of 0.30 A. The battery takes 6 hours to charge fully.Show that the electrical energy supplied in charging the battery is about 20 000 J.

...............................................................................................................................................

...............................................................................................................................................(2)

Calculate the overall efficiency of the process of charging the battery and then using it to play the game.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Efficiency = ...............................................................(3)

(Total 10 marks)

185. In a railway system the rails are exposed to high stresses which can lead to the development of small cracks. For safety the regular testing and monitoring of rails in service is a vital requirement. Ultrasonics can be used as a method of quick, non-destructive testing without removing the rails.

Give one reason why it is important to have a quick, non-destructive method of testing rails without removing them.

...............................................................................................................................................

...............................................................................................................................................(1)

Ultrasonics involves the use of sound waves with frequencies above 20 kHz, the maximum frequency usually audible to human beings.

Describe sound waves passing through a steel rail in terms of the displacement of the particles in the steel.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

The speed of sound in steel is 5900 m s–1 and the frequency used is 4.0 × 106 Hz.

Show that the wavelength of the ultrasonic waves is about 1.5 × 10–3m.

...............................................................................................................................................

...............................................................................................................................................(2)

What is meant by

frequency? ............................................................................................................................

...............................................................................................................................................

wave1ength? .........................................................................................................................

...............................................................................................................................................(3)

Ultrasonic fault detectors are mounted on a special coach which can carry out testing at high speeds. The velocity-time graph below records the motion of the coach while testing a length of track.

2 0

1 0

00 2 0 4 0 6 0 8 0 1 0 0 1 2 0

T i m e / s

V e l o c i t y / m s – 1

Use the graph to find the length of track tested.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Length = ...............................................................(3)

(Total 12 marks)

186. Extract from “The Last Word”, New Scientist magazine.

Question: While listening to the radio tuned to a frequency of94.6 MHz (1 MHz= 1 × 106 Hz), I realised that I could either make the radio signal loud or reduce it almost to nothing by moving about the room or simply by leaning backwards or forwards. What caused this problem?

Answer: The reason for your problem is that radio signals, of wavelength about 3 metres, are being reflected off the walls, floor and ceiling of the room - and, of course, off you. The signals therefore reach the radio by at least two different paths. This leads to an effect called superposition. By trial and error you can place your body in a position to cause this cancellation effect and then by moving by about 75 cm you can hear the signal clearly.

What is meant by superposition?

...............................................................................................................................................

...............................................................................................................................................(2)

Explain why the body in one particular place can cause a cancellation effect.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

Explain why stepping forwards by 75 cm could be enough to change the effect from cancellation to a loud signal.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

(Total 8 marks)

187. A student wants to provide lighting for a model house which she has made. She needs 3.0 V for her lamps but only has a 9.0 V battery, so uses a linear resistor AB in the circuit below. The linear resistor is made from a high resistance uniform conductor.

V

9 . 0 V

L i n e a rr e s i s t o r

A

B

S l i d i n g c o n t a c t

What is the name of the device AB when it is used in this manner?

...............................................................................................................................................(1)

State the voltmeter reading when the sliding contact is at:

A ................................. B .................................(2)

The student moves the sliding contact until the voltmeter reads 3.0 V.

Add an arrow labelled X to the diagram to show where the sliding contact must be placed.(1)

The student replaces the voltmeter with a 3.0 V lamp but the lamp does not light. Explain why the lamp does not light.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

(Total 7 marks)

188. A food packaging factory is moving soup through a 0.075 m diameter pipe when an obstruction occurs in the pipe. An ultrasound probe, connected to an oscilloscope, is moved along the pipe to find the obstruction (figure 1). The oscilloscope trace is shown below(figure 2).

Figure 1

U l t r a s o u n d p r o b e

d i r e c t i o n o fm o t i o n

S o u p

O b s t r u c t i o n

P i p e

Figure 2

1 . 0 c m

A

B

Oscilloscope time base = 20 × 10–6 s cm–1.

On figure 2, pulse A is the outgoing signal from the probe and pulse B is the reflected signal from the other side of the pipe

Calculate the speed of the ultrasound in the liquid in the pipe.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Speed = .............................................................(2)

State one way in which the oscilloscope trace will change when the ultrasound probe is above the obstruction.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(1)

After the obstruction has been cleared, a “Doppler” ultrasound probe is used to measure the speed of the soup in the pipe. Describe the principle of this method.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

What must be measured to determine the speed of the soup?

...............................................................................................................................................

...............................................................................................................................................(1)

Someone says that this would be easier if the soup contained lumps like vegetables. Comment on this suggestion.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(1)

(Total 8 marks)

189. One of the main features of glass is that it is transparent. However, most glass surfaces reflect some of the incident light so that only some of the light is transmitted. This is a particular problem if the glass is to be used for spectacle lenses which may be worn in low light conditions such as when driving at night. The problem can be reduced by the use of a special coating which reduces the amount of reflected light.

The graph below shows the relationship between the percentage of reflected light and the wavelength for two glass surfaces, one of which has been treated with a special non- reflective coating.

1 0

8

6

4

2

0

P e r c e n t a g e o fr e f l e c t e d l i g h t

4 5 0 5 5 0 6 5 0 7 5 0W a v e l e n g t h / n m

N o nc o a t e d

C o a t e d

State the wavelength range for which the coated glass reflects less than 2% of the incident light.

...............................................................................................................................................(1)

Sketch a graph of the percentage of light transmitted by the coated glass surface against wavelength. Add a suitable scale to the y axis.

P e r c e n t a g e o fr e f l e c t e d l i g h t

4 5 0 5 5 0 6 5 0 7 5 0W a v e l e n g t h / n m

(2)

The smallest amount of light is reflected when the wavelength in the coating is about 360 nm. Calculate the wavelength in air. (The refractive index of the coating is 1.38.)

...............................................................................................................................................

...............................................................................................................................................

Wavelength = .............................................................(1)

Explain why the thickness of the coating should be 90 nm to obtain the minimum amount of reflection.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

Light reflected from the glass surface may be plane polarised. Explain the difference between unpolarised and plane polarised light.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 9 marks)

190. The intensity of the light falling on the photocell shown in the diagram below controls the electric current flowing in a circuit.

L i g h t

A n o d e

C a t h o d e–

+

An electron is sometimes released when a photon hits a metal surface. This is known as the photoelectric effect and can be expressed mathematically by the Einstein equation.

hf = 2max2

1 υφ m+

Show that the energy of a photon of light of frequency 6.0 × 1014 Hz is about 4 × 10–19J.

...............................................................................................................................................

...............................................................................................................................................(1)

A student is investigating the photoelectric effect and selects light of various frequencies to shine on to a metal surface. Using his experimental data, he calculates the maximum kinetic energy of the electrons emitted from the surface. The results are given below.

Frequency/1014 HzMaximum kinetic

energy/l0–19 J

7.0 1.65

6.5 1.29

6.0 0.96

5.5 0.65

5.0 0.30

Plot the points on the grid below. Add the line of best fit.

The Einstein equation can be rearranged to give

f = h

m

h

2max2

1 υφ +

7.0

6.0

5.0

4.0

00.

20.

40.

60.

81.

01.

21.

41.

61.

8

Fre

quen

cy/1

0

Hz

14

–19

Max

imum

kin

etic

ene

rgy/

10

J

(4)

Use the graph you have plotted to find a value for h.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

Hence show that φ is about 3 × 10–19 J.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

The student continues the experiment and shines light with a frequency of 4.5 × 1014 Hz on to the surface but finds that he cannot detect any photoelectrons. Explain why photoelectrons are not being emitted from the surface.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 12 marks)

191. The current in the tether would be provided by a solar cell array on MIR. The graph below shows a set of current-voltage (I–V) curves for a particular solar cell for different light intensities. The cell was kept at 25 °C.

3 . 5

3 . 0

2 . 5

2 . 0

1 . 5

1 . 0

0 . 5

0 . 00 . 0 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5 0 . 6

V o l t a g e / V

C u r r e n t / A – 2

– 2

– 2

– 2

– 2

1 0 0 0 W m

7 5 0 W m

4 5 0 W m

3 0 0 W m

1 0 0 W m

Draw a circuit diagram to show how a range of measurements of V and I could be taken for the solar cell at a given light intensity.

(3)

Show that the maximum power available for an intensity of 1000 W m–2 is about 1.4 W.

...............................................................................................................................................

...............................................................................................................................................(2)

It is suggested that maximum power is proportional to light intensity.Without plotting any further graphs, analyse some of the data to comment on whether this suggestion is reasonable.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

Data showing how the e.m.f., ξ , of this cell depends on temperature t is provided in the table below.

ξ /V t/°C

0.62 12

0.59 25

0.54 50

0.51 63

0.48 75

Plot a graph of ξ against t on the grid below.

(4)

Use the graph to determine a mathematical relationship between ξ and t.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(4)

The graph below shows the contribution of different wavelengths of light arriving from the Sun, to the total intensity at a point just above the Earth’s atmosphere.

0 . 2 5

0 . 2 0

0 . 1 5

0 . 1 0

0 . 0 5

0 . 0 00 . 0 1 . 0 2 . 0 3 . 0

W a v e l e n g t h / mµ

I n t e n s i t y p e r u n i tw a v e l e n g t h/ W c m mµ– 2 – 1

This particular solar cell only produces current from light with a wavelength less than or equal to 1.1 × 10–6 m.

Use the graph to determine the light power from the sun that is available for conversion to electrical power in this satellite solar cell. The area of the solar cell is 4.0 cm2.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(4)

(Total 20 marks)

192. The possibility of nuclear fusion experiments in your living room is getting closer! Lasers could be used to deliver a huge pulse of energy in a very short time to a small volume of deuterium (an isotope of hydrogen) to produce the conditions for fusion for just an instant.

A neodymium laser produces 40 J of coherent light of wavelength 1050 nm for a period of 400 fs (1 fs = 10–15 s).

Explain the meaning of the word coherent.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(1)

Calculate the power delivered by this laser.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Power = ......................................(2)

Calculate the energy level change taking place in atoms of neodymium when emitting light of the above wavelength.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(3)

(Total 6 marks)

193. Classify each of the terms in the left-hand column by placing a tick in the relevant box.

Base unit Derived unit Base quantity Derived quantity

Mass

Charge

Joule

Ampere

Volt

(Total 5 marks)

194. A negative temperature coefficient thermistor is used in the following circuit to make a temperature sensor.

m A

6 . 0 V

Explain how the circuit works.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

The graph shows how the resistance of the thermistor varies with temperature.

2 . 0

1 . 0

0 . 00 2 0 4 0 6 0

R / k Ω

θ / ° C

What will the reading on the milliammeter be when the thermistor is at a temperature of 20 °C?

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Milliammeter reading = ....................................(3)

(Total 5 marks)

195. A copper wire has a cross-sectional area of 0.20 ×10–6 m2. Copper has 1.0 × 1029 free electrons per cubic metre.

Calculate the current through the wire when the drift speed of the electrons is 0.94 mm s–1.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Current = .................................................(3)

The wire is 4.0 m long. Copper has a resistivity of 1.7 × 10–8 Ω m. Calculate the resistance of the wire.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Resistance = ............................................(3)

Calculate the potential difference across the wire.

...............................................................................................................................................

Potential difference = ..............................(1)

A second wire with the same dimensions is made from a material that has a greater resistivity than copper. Explain how, if at all, the current will differ from that in the copper wire when the same p.d. is applied across it.

...............................................................................................................................................

...............................................................................................................................................(2)

The number of free electrons per cubic metre in this wire is the same as that in the copper wire. Compare the drift velocities of the free electrons in the two wires.

...............................................................................................................................................

...............................................................................................................................................(1)

(Total 10 marks)

196. A student wants to determine the e.m.f. ε of a cell and its internal resistance r.

He uses the circuit shown and measures the terminal voltage V across the cell and the current I in the circuit for each setting of the variable resistor.

εr

I

A

V

He plots the following graph of terminal voltage V against current I.

V / V

3 . 0

2 . 0

1 . 0

0 . 00 . 0 1 . 0 2 . 0 I / A

Show how the relationship V = ε – Ir can be used with his graph to determine the e.m.f. ε of the cell. State its value.

...............................................................................................................................................

...............................................................................................................................................

E.m.f. = ..........................................(2)

Show how the graph can be used to determine the internal resistance r of the cell.Calculate its value.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Internal resistance = ..............................(2)

The student repeats the experiment using two of these cells in series. On the graph, draw the line that he obtains.

(3)

Suggest why the student includes the filament lamp in the circuit.

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 9 marks)

197. Listed below are four types of wave:

microwave sound ultraviolet infrared

From this list, choose the wave which matches each description in the table below, and write it in the space provided. (You may choose a type of wave once, more than once or not at all.)

Description Type of wave

A wave capable of causing photoelectric emission of electrons

A wave whose vibrations are parallel to the direction of propagation of the wave

A transverse wave of wavelength 5 × 10–6 m

The wave of highest frequency(Total 4 marks)

198. The diagram is a plan view of an experiment to measure the wavelength of microwaves. The diagram is to scale but one third of full size.

S l i t S l i t

M e t a l p l a t e s

T r a n s m i t t e r

X

B

A

O

S C A L E :O n e t h i r d o ff u l l s i z e

As a microwave detector is moved around the arc from A to B, alternate maxima and minima of intensity are observed. Explain why.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(4)

A maximum is observed at point O, and the next maximum at point X. By means of suitable measurements on the diagram determine the wavelength of the microwaves.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Wavelength = ....................................................(3)

A teacher demonstrating this experiment finds that, even at the maxima, the wave intensity is small. A student suggests making the slits wider to let more energy through. Explain why this might not be a good idea.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

For an interference pattern to be observed between waves from two sources, the sources must be coherent. Explain what is meant by coherent, and what makes the two sources in this experiment coherent.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 11 marks)

199. The diagram shows monochromatic radiation falling on a photocell connected to a circuit.

µ A

VV a r i a b l e d . c .s u p p l y

– 6 V t o + 6 VD i g i t a lv o l t m e t e r

A n o d e

P h o t o c a t h o d e

I n c i d e n tm o n o c h r o m a t i cr a d i a t i o n

The incident radiation has a wavelength of 215 mm. The metal surface of the photocathode has a work function of 2.26eV.

Calculate the energy in eV of a photon of the incident radiation.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Energy = ................................................... eV(4)

What is the maximum kinetic energy in eV of the emitted electrons?

...............................................................................................................................................

Maximum k.e. = ....................................... eV

Write down the value of the stopping potential.

Stopping potential = ...............................(2)

If the wavelength and intensity of the incident radiation is kept constant, a graph of the current I through the photocell against applied p.d. V is as shown.

I / Aµ

V / V

Mark a letter S on the graph to show the stopping potential.

The photocathode is replaced with one whose metal surface has a greater work function. On the graph above, sketch how I would vary with V given that the wavelength and intensity of the incident radiation remain unchanged.

(3)(Total 9 marks)

200. Edward notices that a bulb for a torch is marked “1.25 V, 0.40 A”.

Edward and Sarah set up a circuit using the cell and the bulb from the torch to check the values marked on the bulb.

Complete the circuit diagram below adding any necessary additional components.

(2)

The results confirm the values marked on the bulb. Edward wonders why it needs a 1.5 V cell to operate correctly. Sarah says this is because of internal resistance, but can’t say why.

Explain this apparent inconsistency between bulb voltage and cell e.m.f.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Show that the internal resistance of the cell is about 0.6 Ω .

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

Calculate the resistance of this bulb when connected to the cell as above.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Resistance = ................................................(2)

Sarah and Edward then check their result using, an ohmmeter. The ohmmeter uses a very small current which does not light up the bulb. They obtain a resistance value of 0.7 Ω .

Explain why this value of resistance is much lower than the resistance obtained using the circuit above.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 10 marks)

201. High temperatures in the Sun’s atmosphere cause particles such as electrons and protons to be thrown out far into space. When these particles reach the Earth they can cause spectacular colour effects in the sky known as an aurora.

The particles interact with electrons in atoms in the upper atmosphere. As a result, coloured light is emitted. Green light of wavelength 5.58 × 10–7 m is given out from oxygen atoms and red light of wavelength 6.48 × 10–7 m from nitrogen.

Show that the energy of a photon of green light emitted from oxygen is about 3.6 × 10–19 J.

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...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

The diagrams below show the ground state and one excited state for electrons in oxygen and nitrogen. Transitions between these levels give the red and green light in the aurora. Add an arrow to show the electron transition that occurs when a photon of green light is emitted.

(2)(Total 4 marks)

202. Quantum Balls

BUCKYBALLS - spherical molecules made up of 60 carbon atoms - can behave like waves, blurring the boundary between the everyday world and the realm of quantum mechanics.

Markus Arndt and his colleagues at the University of Vienna sent buckyballs through a diffraction grating. A detector beyond the grating showed a clear interference pattern, where waves superimpose, indicating wavelike behaviour. “The interference pattern can only be explained if, in effect, each molecule goes through at least two of the openings” says Anton Zeilincer, who supervised the research.

Zeilinger predicts similar results with objects as large as viruses. He suggests that people think that quantum physics deals with small particles and classical physics deals with large things but that really the quantum world has no boundary.

Based on New Scientist Magazine, vol. 164, issue 2208.

Explain the words below.

Diffraction

...............................................................................................................................................

...............................................................................................................................................

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Superposition

...............................................................................................................................................

...............................................................................................................................................

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Quantum

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(4)

State one other particle you have met in your course which exhibits similar wavelike behaviour.

...............................................................................................................................................(1)

What does this passage tell us about classical and quantum physics?

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................(2)

(Total 7 marks)

203. The resistors R1 and R2 in circuit (i) are equivalent to a single resistor R in circuit (ii).

P

Q

R RR 21

(i) (ii)

In a real circuit it is usually assumed that there is no potential difference between two points, such as P and Q in diagram (i), which are on the same connecting lead. Explain why this is usually a good approximation.

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................(2)

In what circumstances might the approximation break down?

..............................................................................................................................................

..............................................................................................................................................(1)

A laboratory lead consists of 16 strands of fine copper wire twisted together. Each strand is 30 cm long with a diameter of 0.15 mm. Calculate the potential difference across the lead when it is carrying a current of 2.0 A.

(The resistivity of copper = 1.7 × 10–8 Ω m)

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..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

Potential difference =...................................(4)

(Total 10 marks)

204. A beam of microwaves is directed at two slits in a metal sheet. The diagram below shows two adjacent positions P and R where a microwave detector would register maximum readings.

I n c o m i n g

m i c r o w a v e s

M e t a l s h e e tw i t h t w o s l i t s

4 2 0 m m

4 4 2 m m

P

R

N o t t o s c a l e

Use the diagram to determine the wavelength of the microwaves.

..............................................................................................................................................

..............................................................................................................................................

Wavelength = .......................................

Calculate the frequency of the microwaves.

..............................................................................................................................................

..............................................................................................................................................

Frequency = ........................................(4)

On the diagram mark with a Q a position where another maximum reading would occur. On the diagram mark with a D a position where a minimum reading would occur.

(2)

In a similar experiment, sound waves were directed at the same metal sheet. The speed of

sound is 330ms–1 and the frequency of the sound waves was 1100Hz. Explain why a maximum reading would not be detected at P in this experiment.

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(Total 8 marks)

205. The following is a simplified energy level diagram for atomic hydrogen.

0 e V– 0 . 8 5 0 e V

– 1 . 5 1 e V

– 3 . 4 0 e V

– 1 3 . 6 e V G r o u n d s t a t e

State the ionisation energy of atomic hydrogen.

..............................................................................................................................................

..............................................................................................................................................

Account for the labelling of the energy levels with negative numbers.

..............................................................................................................................................

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..............................................................................................................................................(3)

Calculate the wavelength of the photon emitted when an electron moves from the–1.51 eV energy level to the –3.40 eV energy level.

..............................................................................................................................................

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..............................................................................................................................................

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Wavelength = ........................................(3)

Describe how you would produce a line spectrum of atomic hydrogen in a laboratory.

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..............................................................................................................................................(2)

Sketch what you would expect to see.

(1)(Total 9 marks)

206. The current I flowing through a conductor of cross-sectional area A is given by the formula

I = nAQν

where Q is the charge on a charge carrier. Give the meanings of n and ν .

n ...........................................................................................................................................

ν ...........................................................................................................................................(2)

Show that the equation is homogeneous with respect to units.

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..............................................................................................................................................(3)

With reference to the equation, explain the difference between a metal conductor and a plastic insulator.

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(Total 7 marks)

207. A student is planning an experiment to measure the resistivity of aluminium. She plans to use an ohmmeter to measure the resistance of a rectangular strip of aluminium foil fastened between two bulldog clips.

Ω

w

l

F o i l s t r i p

B u l l d o g c l i p

O h m m e t e r

She also intends to measure the thickness t of the foil and the length 1 and width w of the strip.

Explain how she should calculate the resistivity from her measurements.

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The student decides that for sufficient accuracy the resistance of the strip must be at least 1.0 Ω . To see what dimensions would be suitable, she does some preliminary experiments using strips 20 mm wide cut from foil 0.15 mm thick. She finds that for strips of a convenient length the resistance is far too small.

Calculate the length of strip, 20 mm wide and 0.15 mm thick, which would have a resistance of

1.0 Ω (Resistivity of aluminium = 2.7 × 10–8Ω m)

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

Length =.......................................................(3)

Suggest a way, other than increasing its length, by which she could increase the resistance of her strip. Comment on whether this change would lead to a more precise measurement of the resistivity.

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(Total 7 marks)

208. The diagram below shows a cell, of e.m.f. ε and internal resistance r, driving a current I through an external resistance R.

ε

r

R

I

Using these symbols, write down a formula for

(i) the power dissipated in the external resistance

....................................................................................................................................

(ii) the power dissipated in the internal resistance

....................................................................................................................................

(iii) the rate of conversion of chemical energy in the cell

....................................................................................................................................

Using these formulae, write down an equation expressing conservation of energy in the circuit,

and hence show that I = )( rR +

ε

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..............................................................................................................................................(5)

The equation I = ε / (R + r) shows that the internal resistance of a power supply limits the current which can be drawn from it. Explain this.

..............................................................................................................................................

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..............................................................................................................................................(2)

A 5 kV laboratory supply can be made safe for student use by connecting an internal series resistor. The following resistors are available:

l kΩ 10 kΩ 100 kΩ 1 MΩ

Explain which resistor should be used to make the supply as safe as possible.

..............................................................................................................................................

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..............................................................................................................................................(2)

(Total 9 marks)

209. The graph shows the current-voltage characteristic of a semiconductor diode.

1 0 0

8 0

6 0

4 0

2 0

00 0 . 2 0 . 4 0 . 6 0 . 8

V / V

I / m A

State, with a reason, whether the diode obeys Ohm’s law.

..............................................................................................................................................

..............................................................................................................................................(1)

Show that when the voltage across the diode is 0.74 V its resistance is about 9 Ω .

..............................................................................................................................................

..............................................................................................................................................(2)

When the diode is connected in the following circuit, the voltage across it is 0.74 V.

+ 9 . 0 V

0 V

R

Calculate the value of the resistance R.

..............................................................................................................................................

..............................................................................................................................................

..............................................................................................................................................

R = .............................................(3)

Electronic circuit designers often use a simple model of this type of diode. This “model diode” has the following properties:

(i) For any voltage below +0.7 V it does not conduct at all.

(ii) Once the voltage reaches +0.7 V the diode can pass any size of current with no further increase in voltage.

Add a second graph to the grid above to show the current-voltage characteristic of this model diode.

(2)(Total 8 marks)

210. Define electrical potential difference.

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..............................................................................................................................................(1)

State an appropriate unit for potential difference.

..............................................................................................................................................(1)

Express this unit in terms of base units.

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(Total 4 marks)

211. White Lightning is an electric car which held the world speed record for such a vehicle in 1999.

White Lightning on Bonneville Salt Flats

Some data about White Lightning:

Maximum speed reached = 107ms–1

Mass of vehicle plus driver = 1160kgVoltage provided by battery when delivering power = 420 VPower input to main motor = 300 kWTime to reach maximum speed = 100s

Show that the current in the motor is about 700 A.

...............................................................................................................................................

...............................................................................................................................................(1)

Suggest one problem that a current of this size might give the designer.

...............................................................................................................................................

...............................................................................................................................................(1)

Explain why the e.m.f. of the battery would have to be more than 420 V.

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...............................................................................................................................................(2)

Show that the overall efficiency of the vehicle is about 20% during a run up to full speed.

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...............................................................................................................................................(3)

Suggest two reasons for the energy losses of about 80%.

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...............................................................................................................................................(2)

(Total 9 marks)

212. A musician who is also a physicist makes measurements on the strings of her harp. She chooses three of the nylon strings - the one at each end, and one near the middle. For each one she measures the length, the diameter and the frequency of the fundamental note produced when the string is plucked. She then constructs a spreadsheet to calculate the mass per unit length, the wave speed, and the tension in each string. Measured data is in bold; calculated values are in plain text. See below

A B C D F G H I

1 stringnumber

length/m

diam/mm

frequency/Hz

volume of1 metre

length/m3

mass perunit

length/kg m–1

wavespeed/m s–1

tension

/N

2

3 1 0.08 0.7 2048 0.00000038 0.000437 328 47

4 22 0.52 1.0 256 0.00000079 266 64

5 36 1.20 2.5 64 0.00000491 0.005646 154 133

6

7 mass of a cubic metre of nylon/kg

8 1150.00

Explain why the formula in cell H3 is

=2*B3*D3

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...............................................................................................................................................(2)

Show how the value in cell F5 is calculated using the measurement in cell C5.

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...............................................................................................................................................(2)

The value in cell G4 is not shown. Calculate what it should be.

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Value = ………………………..(2)

Give an appropriate formula for cell I3 in terms of cells G3 and H3. Explain how you arrive at this formula.

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...............................................................................................................................................(2)

A friend says he has read that a harp is constructed so that all the strings are at about the same tension.

Comment on this idea

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(Total 11 marks)

213. The diagram shows a strain gauge. The resistance of this device changes when it is deformed. It is used on bridges to monitor any changes such as flexing at the joints or extension of the supporting cables.

The strain gauge consists of a length of very fine wire, looped as shown, which has been cemented between two sheets of very thin paper. It is firmly glued to the surface that is to be monitored.

Explain why the resistance of the strain gauge changes when it is stretched.

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...............................................................................................................................................(2)

Explain an advantage of using the arrangement of wire shown in the diagram.

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...............................................................................................................................................(1)

Draw a diagram showing a circuit you could use to measure the resistance of the strain gauge.

(2)

The wire used for the gauge is 0.20 m long and has a diameter of 2.0 × 10–4 m. Show that this wire has a resistance of about 3 Ω .

Resistivity = 4.9 × 10–7 Ω m

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(Total 8 marks)

214. Read the following passage and answer the questions which follow.

Diffraction

Light bends when it passes around an edge or through a slit. This effect is called diffraction. The angle through which the light bends is proportional to the wavelength of the light. Red light bends about 50% more than blue light.

The pattern of light and dark created when light passes through two slits shows that light has wave properties. The light waves that go through the slits spread out, overlap and add together to produce the pattern. In fact, the spacing between two adjacent dark bands in the pattern is inversely proportional to the slit separation.

Adapted from the website of the Exploratorium San Francisco

Use diagrams to explain how two waves overlap to produce a dark band.

(2)

Use the information in the passage to calculate an approximate wavelength for red light.Assume that the wavelength of blue light equals 460 nm.

...............................................................................................................................................

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...............................................................................................................................................(2)

Blue light is shone through two slits separated by 0.10mm and adjacent dark bands in the pattern are 8.0 mm apart.

How far apart will the dark bands be if the slit separation is doubled?

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...............................................................................................................................................(1)

The website also states that the diffraction pattern produced when sunlight passes through a feather consists of bands of light with coloured edges. Explain how this pattern occurs.

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(Total 8 marks)

215. Scientists from Leeds University are involved in an experiment at the South Pole to look for cosmic radiation from a supernova observed in 1987. Cosmic radiation consists of high energy particles from space.

Their equipment involves the following:

C o s m i c r a d i a t i o n

T r a n s p a r e n tp l a s t i c b l o c k

L i g h t

P h o t o m u l t i p l i e r

C o m p u t e r

Cosmic radiation causes this plastic block to emit light. If this light enters the photomultiplier, photoelectrons are released and the signal is sent to a computer which records the event.

A photomultiplier which has a photocathode made from antimony–caesium has a threshold wavelength of 700 nm. Explain why a photocathode has a threshold wavelength.

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...............................................................................................................................................(4)

Show that the work function of antimony-caesium is about 3 × 10–19 J.

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...............................................................................................................................................(3)

The scientists’ generator at the South Pole produces a voltage of 600 V and the photomultiplier needs potential differences of 200 V, 400 V and 600 V. Draw a circuit to show how a series of resistors could provide all of these potential differences from one 600 V supply.

(2)

Suggest why cosmic radiation from the supernova was not detected at the same time as the supernova was observed.

...............................................................................................................................................

...............................................................................................................................................(1)

(Total 10 marks)

216. A photographer uses a polarising filter over the camera lens. She notices that the intensity of the light received from the blue sky changes as she rotates the filter.

What does this suggest about light from the sky?

...............................................................................................................................................

...............................................................................................................................................(1)

Explain the change in intensity as the filter is rotated.

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...............................................................................................................................................(2)

The use of a polarising filter makes a blue sky appear darker, but the clouds remain bright.

Suggest why there is little change in the intensity of the light from the clouds.

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...............................................................................................................................................(1)

Astronomers notice the same effect with the radio waves emitted by some galaxies.What does this suggest about these radio waves?

...............................................................................................................................................

...............................................................................................................................................(1)

State why radio waves should behave in the same way as light.

...............................................................................................................................................

...............................................................................................................................................(1)

(Total 6 marks)

217. The current I through a metal wire of cross-sectional area A is given by the formula

I = nAυ e

where e is the electronic charge on the electron. Define the symbols n and υ .

...............................................................................................................................................

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...............................................................................................................................................

...............................................................................................................................................(2)

Two pieces of copper wire, X and Y, are joined end-to-end and connected to a battery by wires which are shown as dotted lines in the diagram. The cross-sectional area of X is double that of Y.

X

Y

In the table below, nx and ny denote the values of n in X and Y, and similarly for the other quantities. Write in the table the value of each ratio, and alongside it explain your answer.

Ratio Value Explanation

X

Y

n

n

X

Y

I

I

X

Y

υυ

(6)(Total 8 marks)

218. An electric shower is connected to the mains supply by a copper cable 20 m long. The two

conductors inside the cable each have a cross-sectional area of 4.0 mm2 . The resistivity of

copper is 1.7 × 10–8 Ω . Show that the resistance of each of the conductors is 0.085 Ω .

...............................................................................................................................................

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...............................................................................................................................................(2)

The operating current of the shower is 37 A. Calculate the total voltage drop caused by the cable supplying the shower.

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Voltage =...........................................(2)

Explain why cable with 6.0 mm2 conductors would have been more suitable for this shower installation.

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...............................................................................................................................................(2)

(Total 6 marks)

219. Ultraviolet light of wavelength 12.2 nm is shone on to a metal surface. The work function of the metal is 6.20 eV.

Calculate the maximum kinetic energy of the emitted photoelectrons.

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

...............................................................................................................................................

Kinetic energy =..................................

Show that the maximum speed of these photoelectrons is approximately 6 ×106 ms–1.

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...............................................................................................................................................(Total 5 marks)

220. Melanie is using a spreadsheet to model the behaviour of the circuit shown below.

E

I

r

R

B a t t e r y

V

A B C D E F

1 Calculations for a Battery Delivering Power

2

3 e.m.f. internalresistance

loadresistor

current p.d. acrossload

power inload

4 E r R I V P

5 (volts) (ohms) (ohms) (amps) (volts) (watts)

6

7 12.0 2.00 0.00 6.00 0.00 0.0

8 12.0 2.00 0.50 4.80 2.40 11.5

9 12.0 2.00 1.00 4.00 4.00 16.0

10 12.0 2.00 1.50 3.43 5.14 17.6

11 12.0 2.00 2.00 3.00 6.00 18.0

12 12.0 2.00 2.50 2.67 6.67 17.8

13 12.0 2.00 3.00 2.40 7.20 17.3

14 12.0 2.00 3.50 2.18 7.64 16.7

15 12.0 2.00 4.00 2.00 8.00 16.0

To calculate a value for cell D7, Melanie entered this formula:

= A7/(B7 + C7)

Explain why this is correct.

................................................................................................................................................

................................................................................................................................................(1)

What would be an appropriate formula for cell E9?

................................................................................................................................................(1)

What would be an appropriate formula for cell F11?

................................................................................................................................................(1)

What is the short-circuit current obtainable from this battery?

................................................................................................................................................(1)

Explain why the p.d. across the load resistor increases as the current falls.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

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................................................................................................................................................(2)

Sketch a graph on the axes below to show how the power in the load would vary for load resistors in the range 0–9 Ω (marking values where appropriate).

P / W

0 R / Ω(3)

Comment on one key feature of the graph.

................................................................................................................................................

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................................................................................................................................................(2)

(Total 11 marks)

221. Babies’ food sometimes carries the following warning: “Do not warm feeds in a microwave oven as this may cause uneven heating and could scald your baby’s mouth”.

An Internet site gives the following explanation:

Coherent microwaves are emitted in all directions from a source within the oven. The waves reflect off the metal walls so that the microwave radiation reaching any particular point arrives from several different directions. The waves interfere and set up standing waves. This produces the pattern of hot and cold zones observed in food heated in a microwave oven.

" H o t z o n e "

" C o l d z o n e "

Explain the meanings of the following words from the passage.

Coherent ................................................................................................................................

................................................................................................................................................(1)

Standing wave ………………………………………………………………………………

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................................................................................................................................................

................................................................................................................................................(2)

On the diagram above, mark a possible position of one antinode, and label it A.(1)

The frequency of the radiation used in a microwave oven is 2.45 × 109 Hz.

Show that the wavelength of the microwave radiation is about 12 cm.

................................................................................................................................................

................................................................................................................................................(1)

The diagram shows two different paths by which microwaves can reach the point X.

2 0 . 0 c m

2 2 . 1 c m

1 4 . 0 c m

1 0 . 0 c m

M i c r o w a v e s o u r c e

N o t t o s c a l e

Find the path difference for waves reaching point X by the paths shown.

................................................................................................................................................

................................................................................................................................................

Path difference = …………………………(1)

Assuming waves do not reach point X along any other path, explain whether you would expect this point to be a microwave node or antinode.

………………………………………………………………………………………………

………………………………………………………………………………………………

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………………………………………………………………………………………………(3)

Some microwave ovens use two separate microwave frequencies to overcome the problem of uneven heating. Explain how this helps.

………………………………………………………………………………………………

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………………………………………………………………………………………………(2)

(Total 11 marks)

222. Astronomers can identify different gases present in the outer parts of stars by analysing the line spectra of the starlight.

Explain the meaning of line spectra.

………………………………………………………………………………………………

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………………………………………………………………………………………………(2)

Explain how line spectra provide evidence for the existence of energy levels in atoms.

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(Total 5 marks)

223. An ocean can be considered to be made up of two layers: a layer of warm water and a layer of cold water. The interface between them is called a thermocline.

Why does the warm surface water float above the cold deep ocean water?

………………………………………………………………………………………………

………………………………………………………………………………………………(1)

W a r ms u r f a c el a y e r

C o l dl a y e r

O c e a n s u r f a c e

T h e r m o c l i n e

S u b m a r i n e

A surface ship uses sonar to detect submarines. Explain why the ultrasound waves travelling through the water partially reflect from the thermocline.

………………………………………………………………………………………………

………………………………………………………………………………………………(1)

Explain why a submarine travelling in the cold water just below the thermocline is very difficult to detect using surface sonar.

………………………………………………………………………………………………

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………………………………………………………………………………………………(2)

Some scientists believe that the passage of a submarine could distort the thermocline and cause the surface of the ocean to bulge as shown. They think that they may be able to detect this bulge using radar from a satellite.

Explain why sonar cannot be used from a satellite.

………………………………………………………………………………………………

………………………………………………………………………………………………(1)

A satellite is in orbit 6.0 × 107 m above the surface of the Earth and uses radar to measure the distance to the ocean surface. Calculate the time between the emission and detection of a radar pulse which strikes the surface of the ocean directly below the satellite.

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………

Time = ………………………..(2)

The satellite’s timing equipment is capable of measuring time to a precision of 1.0 × 10–9 s.

Calculate the minimum change in the height of the ocean which the satellite is capable of detecting.

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………

Minimum change = ………………………..(2)

Suggest a possible problem in detecting submarines in this way.

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………(1)

(Total 10 marks)

224. Farmers can choose the best time to harvest some fruits by measuring how much sugar their juice contains. The concentration of sugar in the juice alters its refractive index which can be measured with a refractometer. Figure 1 shows a beam of light entering a refractometer. The juice is placed on top of the prism.

P r i s m

C a l i b r a t e d s c a l eL i g h t b e a m

J u i c e

Figure 1

The light coming out of the prism hits the scale as shown in figure 1. Explain why part of the scale appears dark.

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………

………………………………………………………………………………………………(2)

A student uses a prism to investigate this effect in the school laboratory. A layer of juice is trapped between the prism and a microscope slide. Figure 2 below shows a ray of light hitting the surface between the prism and the juice at the critical angle.

M i c r o s c o p e s l i d e

P r i s m

J u i c e l a y e r

Figure 2

Mark the following angles on figure 2 opposite:

the critical angle Can incident angle ia refracted angle r

(3)

Explain the term critical angle.

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The student calculates these values of refractive index for different concentrations of sugar solution.

Concentration of sugarsolution/%

Refractive index of sugar solution

0 1.333

15 1.356

30 1.381

45 1.410

60 1.442

Plot a graph of these results on the grid below.

(4)

From the graph, find the refractive index of a sugar solution of concentration 40%.

Refractive index: ...................................................................................................................(1)

(Total 12 marks)

225. (a) Describe how you would determine by experiment approximate values for the e.m.f and internal resistance of a torch battery. Include a circuit diagram.

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(b) (i) A battery has an e.m.f. of 12.0 V and an internal resistance of 3.0Ω .Calculate the p.d. across the battery when it is delivering a current of 3.0 A.

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p.d. = ..............................................(2)

(ii) The same battery is now connected to a filament lamp. The graph shows how the p.d. across the lamp would depend on the current through it.

0 . 5 1 . 0 1 . 5 2 . 0 2 . 5 3 . 0

1 2

1 0

8

6

4

2

0

V / V

I / A

Use your answer to part (i) to help you draw, on the same axes, a line showing how the p.d. across the battery would depend on the current through it.

(1)

What current will the battery drive through the lamp?

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(Total 8 marks)

226. The graph shows how the resistance R of a thermistor depends on temperature θ .

θ

R

In terms of the behaviour of the material of the thermistor, explain qualitatively the variation shown on the graph.

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A student connects the thermistor in series with a 330 Ω resistor and applies a potential difference of 2.0 V. A high resistance voltmeter connected in parallel with the resistor reads 0.80 V.

V

3 3 0 Ω

2 . 0 V

Calculate the resistance of the thermistor.

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Resistance = ........................................(3)

The student now increases the applied p.d. from 2.0 V to 20 V. She expects the voltmeter reading to increase from 0.80 V to 8.0 V but is surprised to find that it is greater. Explain this.

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(Total 8 marks)

227. Under what circumstances could two progressive waves produce a stationary (standing) wave?

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Describe with the aid of a diagram an experiment using microwaves to produce stationary (standing) waves.

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How would you show that a stationary wave had been produced?

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(Total 5 marks)

228. The diagram shows part of a stretched slinky spring and the same section of the spring when a longitudinal wave is travelling along it.

The dotted vertical lines show the positions of two coils which at this moment are undisplaced.

Mark on the lower diagram a compression C and a rarefaction R

Measure the wavelength of the wave

Wavelength ..........................................................................................................................

Mark on the lower diagram a coil with maximum displacement, M.

Measure the amplitude of the wave, i.e. the displacement of coil M.

Amplitude .............................................................................................................................(Total 4 marks)

229. The diagram shows apparatus which can be used to demonstrate the photoelectric effect.

S o u r c e o f m o n o c h r o m a t i ce l e c t r o m a g n e t i c r a d i a t i o n

I n s u l a t o r

N e g a t i v e l y c h a r g e dz i n c p l a t e

T h i n g o l d f o i l

M e t a l r o d

E l e c t r o s c o p e

The deflection of the thin gold foil is a measure of the charge stored on the zinc plate.

When ultraviolet light is directed towards the zinc plate, the thin gold foil gradually returns to the vertical.

When red light is used the thin gold foil stays in the position shown.

How does the particle theory of light explain these observations?

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What would be observed if electromagnetic radiation of greater intensity were used?

Ultraviolet of greater intensity ............................................................................................

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Red light of greater intensity ...............................................................................................

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What would be observed if the zinc plate and electroscope were positively charged? Explain your answer.

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(Total 8 marks)

230. The diagram shows some of the energy levels for atomic hydrogen.

0 e V– 1 . 5 1 e V– 3 . 3 9 e V

– 1 3 . 6 e V

Add arrows to the diagram showing all the single transitions which could ionise the atom.(2)

Why is the level labelled –13.6eV called the ground state?

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Identify the transition which would result in the emission of light of wavelength 660 nm.

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Transition = ....................................(4)

(Total 7 marks)

231. You are asked to set up a circuit to take some measurements and to draw a graph which shows how the current in a 12 V, 24 W electric filament lamp varies with the potential difference across it.

The diagram shows the electrical components you will need. Complete a suitable circuit diagram by drawing the connection wires.

–

+

0 – 1 2 V

A

V

(2)

What measurements would you make using this circuit?

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Sketch and label the graph you would expect to obtain.

(3)(Total 8 marks)

232. A torch has three identical cells, each of e.m.f. 1.5 V, and a lamp which is labelled 3.5 V, 0.3 A.Draw a circuit diagram for the torch.

(2)

Assume that the lamp is lit to normal brightness and that the connections have negligible resistance. Mark on your diagram the voltage across each circuit component and the current flowing in the lamp.

(3)

Calculate the internal resistance of one of these cells.

Resistance = .............................……….(3)

(Total 8 marks)

233. Monochromatic light of constant intensity falls on a photocell. The graph shows how the current in the photocell varies with the potential difference applied across it.

I / Aµ

– 1 0 + 1 p . d . / V

0 . 2

0 . 1

The frequency of the incident light is 6.0 × 1014 Hz. Use the graph to estimate the work function of the metal which forms the cathode of the photocell.

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Work function = ……….........……...............(3)

Add to the axes above the graph obtained when only the intensity of the light is increased. Label this graph A.

Add to the axes above the graph obtained when only the frequency of the light is increased. Label this graph B.

(4)(Total 7 marks)

234. The diagram shows wavefronts spreading out from two identical sources, S1 and S2.

S 1

S 2

Describe how such a pattern could be produced and observed using a ripple tank.

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On the diagram draw the following:

(i) a line labelled A joining points where the waves from S1 and S2 have travelled equal distances,

(ii) a line labelled B joining points where the waves from S1 have travelled one wavelength further than the waves from S2,

(iii) a line labelled C joining points where the waves from S2 have travelled half a wavelength further than the waves from S1.

(4)(Total 9 marks)

235. A muon is a particle which has the same charge as an electron but its mass is 207 times the mass of an electron.

An unusual atom similar to hydrogen has been created, consisting of a muon orbiting a single proton. An energy level diagram for this atom is shown.

0 e V

– 3 1 2 e V

– 7 0 3 e V

– 2 8 1 0 e V G r o u n d s t a t e

State the ionisation energy of this atom.

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Calculate the maximum possible wavelength of a photon which, when absorbed, would be able to ionise this atom.

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Maximum wavelength =............................................

To which part of the electromagnetic spectrum does this photon belong?

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Calculate the de Broglie wavelength of a muon travelling at 11% of the speed of light.

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Wavelength =........................................................(3)

(Total 8 marks)

236. Experiments on the photoelectric effect show that

• the kinetic energy of photoelectrons released depends upon the frequency of the incident light and not on its intensity,

• light below a certain threshold frequency cannot release photoelectrons.

How do these conclusions support a particle theory but not a wave theory of light?

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Calculate the threshold wavelength for a metal surface which has a work function of 6.2 eV.

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Threshold wavelength = ………………………………………….

To which part of the electromagnetic spectrum does this wavelength belong?

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(Total 10 marks)

237. The diagram below shows a loudspeaker which sends a note of constant frequency towards a vertical metal sheet. As the microphone is moved between the loudspeaker and the metal sheet the amplitude of the vertical trace on the oscilloscope continually changes several times between maximum and minimum values. This shows that a stationary wave has been set up in the space between the loudspeaker and the metal sheet.

M e t a ls h e e tL o u d s p e a k e r

M i c r o p h o n e

T o o s c i l l o s c o p e( t i m e b a s e o f f )

S i g n a lg e n e r a t o r

How has the stationary wave been produced?

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State how the stationary wave pattern changes when the frequency of the signal generator is doubled. Explain your answer.

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What measurements would you take, and how would you use them, to calculate the speed of sound in air?

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Suggest why the minima detected near the sheet are much smaller than those detected near the loudspeaker.

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(Total 10 marks)