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PRE-LEAVING CERTIFICATE EXAMINATION, 2010

MARKING SCHEME

PHYSICS

HIGHER AND ORDINARY LEVEL

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In considering this marking scheme the following points should be noted:

1. In many instances only key words are given, words that must appear in the correct context in the candidate’s answer in order to merit the assigned marks.

2. Words, expressions or statements separated by a solidus, /, are alternatives which are equally acceptable.

3. Answers that are separated by a double solidus, //, are answers which are mutually exclusive. A partial answer from one side of the // may not be taken in conjunction with a partial answer from the other side.

4. The descriptions, methods and defi nitions in the scheme are not exhaustive and alternative valid answers are acceptable.

5. The detail required in any answer is determined by the context and manner in which the question is asked and by the number of marks assigned to the answer in the examination paper. Therefore, in any instance, it may vary from year to year.

6. For lack of units, or incorrect units, one mark is deducted, as indicated.

7. Each time an arithmetical slip occurs in a calculation one mark is deducted.

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HIGHER LEVEL SECTION A (120 marks)

1. A 2.0 kg object moving with a velocity of 8.0 ms–1 collides with a 4.0 kg object moving with a velocity of 5.0 ms–1 along the same line. If the two objects join together on impact, calculate their common velocity when they are initially

(i) in the same direction m1u1 + m2u2 = m1v + m2v … using v1 = v2 = v (3)

2(8) + 4(5) = 6v v = 36/6 or 6 ms–1 (3) (ii) in opposite directions.

2(8) + (– 4)(5) = 6v1 ... using v1 = common velocity (3) v1 = –0.67ms–1 (3)

(–1 for omission of or incorrect unit) (12) Describe the apparatus which might have been used to do this experiment in the laboratory. (9) air track / smooth runway (3)

two riders / two trolleys (3)cork-pin or velcro for coalescing // means to measure v (3)What would be used to ensure the two objects join together on impact? (6)Cork-pin / velcro / magnets etc. (3 + 3)What readings needed to be taken in order to calculate the velocity? (6)Distance (3)Time (3)Why does this experiment need to be carried out within a closed system? (7)

No external forces (3)Obey principle of conservation of momentum. (4)

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0.2

0.2

0.4

0.6

0.8

1.0

0.4 0.6

sin r

sin i

0.8 1.0

2. A student passed a ray of light through a rectangular glass block from air. He measured the angles of incidence for fi ve rays of light entering the glass block and the corresponding angles of refraction. The following results were obtained:

i/degrees 30° 40° 50° 60° 70°r/degrees 20° 25°30` 32° 35° 39°

Draw a suitable graph and explain how this verifi es Snell’s law. (15) Sin and sin r correct values (– 1 for each incorrect value) (3) Labelled axes (3) At least 4 points plotted correctly. (3) Straight line drawn with good distribution of points. (3) Conclusion: e.g. sin i proportional to sin r / straight line through the origin. (3) From the graph determine the refractive index of the glass. (9)

Correct method for slope e.g. (m=) y2 – y1 / x2 – x1 (3) Substitute coordinates of two points on the graph. (3) n = 1.47 (accept range: 1.44 – 1.50) (3) Which value of r would be the least accurate result? Explain. (6) 20° / 25°30' (3) (Small value gives rise to) larger percentage error (3)

Describe another experiment to determine the refractive index of the glass block. (Include the formula used.) (10)

Apparatus: 2 pins, plane mirror, glass block. (3) Method: Position of no parallax (between object pin and image of 2nd pin) (3) Results: Measure real depth and apparent depth. (2) Refractive index = Real depth ÷ Apparent depth. (2)

sin i 0.50 0.64 0.77 0.87 0.94sin r 0.34 0.43 0.53 0.57 0.63

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3. In a experiment to investigate the variation of the fundamental frequency of a string with its length, the following results were obtained:

l/cm 20 30 40 50 60 70 80 90 100f/Hz 675 455 335 273 230 193 173 150 134

How would the student have known that the string was vibrating at its fundamental frequency? (6)

Paper rider on string / nodes / node / antinode (3) falls off / at bridges / at slit or bridge / at centre (3) (correct diagram merits 2 3)

Draw a suitable graph to illustrate the relationship between the fundamental frequency and the length of the stretched string. State this relationship. (15)

1/l calculated (3) Label axes (3) At least 6 points plotted correctly (3) Straight line drawn with good distribution of points (3) Relationship: f α 1/l (No graph paper – lose 3 m)

Determine from the graph the ratio of the tension to the mass per unit length. (12) Use y2 – y1 / x2 – x1 with 2 points from graph (3) Slope = 138.6 (3) (Use f = 1/2l T/μ to) fi nd T : μ = (2 Slope)2 (3) (Ratio =) 7.7 104 Nm/Kg (3)

Explain how the temperature would affect this value. (7) As temperature is increased, length increases (expands) / mass per unit length decreases (4) Ratio of T:μ increases (with temperature) (3)

1/l (m–1) 5 3.3 2.5 2.0 1.7 1.4 1.25 1.1 1.0f (Hz) 675 455 335 273 230 193 173 150 134

1

100

200

300

400

500

600

700

2 3

f (Hz)

(m –1)

4 5

1l

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4. The electrical resistance per metre of nichrome wire was measured at different diameters. The results are as follows:

Diameter/mm 0.815 0.458 0.28 0.188 0.158 0.118Resistance/Ωm–1 2.04 6.44 17.32 38.2 54.52 99

Name the apparatus used to measure the diameter of wire. Why is advisable to measure the diameter of any wire more than once? (6)

Mircometer (3) Determine average diameter / Wire may be non-uniform (3)

Assuming that each piece of wire is of circular cross-section, calculate the cross-sectional area A of each wire. (9)

1st value calculated (5.21 10–7 m2) (3) Next 3 values (1.64 10–7, 6.1 10–8, 2.7 10–8 m2) (3) Last 2 values (1.9 10–8, 1.1 10–8 m2) (3)

Draw a suitable graph to illustrate the relationship between R and A. (15) 1/A calculated (3) Label axes (3) At least 5 points plotted correctly (3) Straight line drawn with good distribution of points (3) Relationship: R α 1/A (3) Use your graph to estimate the resistivity of the alloy nichrome. (10) Use y2 – y1 / x2 – x1, with 2 points from graph. (3) Slope = 1.02 10–6 (3) As l = 1 m, Slope RA/l → Resistivity = 1.02 10–6 Ωm (4)

R (Ω) 2.04 6.44 17.32 38.2 54.52 991/A ( 106 m2) 1.9 6.1 16.4 37 52.6 90.6

20

20

40

60

80

100

40 60

R (Ω)

( 10 6m2)

80 100

1A

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SECTION B (280 marks)

5. Answer any eight of the following parts (a), (b), (c) etc.

(a) When would an object moving at constant speed have an acceleration? (7) (Following a) Circular path (7)

(b) If the potential energy of a body is 980J at a height of 2 m, what is the weight of the body? (7)

Weight = mg = PE/h = 490J (7) P.E. = Weight only (3)

(c) The critical angle for water is 48.6°. Find its refractive index. (7) sin c = 1/n / n = 1/sin c (4) n = 1.33 (3)

(d) A diffraction grating has 500 lines per mm. What is the distance in metres between adjacent lines? (7)

500 lines = 1 mm = 0.001 m (3) (d = ) 0.000002 m / 2 10–6 m (7)

(e) Give a use of capacitors. (7) Stores energy / separate d.c. from a.c. / smooth output from rectifi er (7)

(f) State Lenz’ law. (7) Direction of (induced) current / voltage / emf (3) Opposes change causing it (4)

(g) Who discovered radioactivity in 1890? (7) Becquerel (7)

(h) What initiates the fi ssion of a uranium nucleus? (7) Neutron (7)

(i) Name 2 factors on which the back emf of a motor depends? (7) Magnetic fl ux density and length of conductor / magnetic fl ux (4) Speed of motor (3)

(j) Distinguish between baryons and leptons. (7) Baryons: mass ≥ Mproton / 3 quarks (3 antiquarks) / Does feel strong force (4) Lepton: me < mass < Mp / quark and antiquark / Does not feel strong force (3) or State the principle of moving coil meters. (7) Current-carrying conductor in a magnetic fi eld (4) Experiences a force (3)

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6. Distinguish between a scalar quantity and a vector quantity. (6) Scalar: Magnitude only (3) Vector: Magnitude and direction. (3)

Describe an experiment to fi nd the resultant of two vectors. (18) 3 (Newton) balances / 3 weights (6) Joined by string / joined over pulleys (3) Adjust until system is at rest (3) Read each force / balance (3) Vector sum of two forces = third force (stated or implied). (3)

Defi ne acceleration (6) Rate of change // (v – u) / t (3) of velocity // explain notation. (3)

A body is travelling with a velocity u in a certain direction. It then accelerates uniformly

in the same direction for a time t. Derive an expression for its displacements after time t in terms of u and a. (11)

Average velocity = (u + v) / 2 s = 1/2 (u + v) t (3) (As v = u + at) s = 1/2 (u + u + at) t (3) s = 1/2 (2ut + at2) (3) s = ut + 1/2 at2 (2)

A car accelerates uniformly from rest to a speed of 15ms–1 in a time of 4 seconds. It then moves at a constant speed for the next 6 seconds.

Calculate: (i) the total distance travelled by the car. (ii) the average speed of the car over the whole journey. (15) (i) For 1st 4 seconds: a = (v – u) / t = (15 – 0) / 4 = 3.75 ms–2 (3) s = ut + 1/2 at2 = 0 + 1/2 (3.75) (4)2 = 30 m (3) For fi nal 6 seconds s = v t = 15(6) = 90 m (3) Total distance = 30 + 90 = 120 m (3) (ii) Average speed = s/t = 120/10 = 12 ms–1 (3)

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7. Explain the term resonance. Give an example of resonance. (9) Transfer of energy between bodies / response to stimulus (vibrations) (3) Correct reference to natural frequency (3) Eg: Singer breaking glass / Buildings in earthquake, etc. (3)

A tuning fork is set vibrating over a resonance tube which can be varied from 0 cm to 110 cm in length. At what lengths would you expect to fi nd resonance if the tuning fork has a frequency of 425Hz and the speed of sound is 340ms–1. (12)

1st position: λ = 1/4 l1 (3) l1 = c/4f = 340/4(425) = 0.2 m (3) 2nd position: (λ = 3/4l2) l2 = 3c/4f = 0.6 m (3) 3rd position: λ = 5/4l3 l3 = 5c/4f = 1.0 m (3)

In the laboratory, the vibrating tuning fork is held slightly above the resonance tube. How is this error in the measurement of length overcome? (6)

Measure diameter of (resonance) tube (3) Length = l + 0.3 d (3)

A police car siren emits a continuous note of frequency 1 kHz as it passes a stationary observer at the traffi c lights. If the police car travels at 30ms–1 towards the observer, the frequency of the note appears to be higher.

Explain with the aid of a diagram, why the frequency of the note appears higher to the observer. Name this phenomen. (14)

Non-concentric circles (– 1 if not labelled as waves) (3) Source and direction of motion (stated/implied) (3) Position of observer indicated (3) Shorter wavelength / higher frequency on approaching observer (3) Name: Dopper effect. (2)

If the velocity of sound is 336ms–1 on this particular day, what is the frequency heard by the observer when the car is: (i) approaching the observer (ii) moving away from the observer? Give another application of this phenomen. (15) (i) Approaching fcf

c u′ =

− (3)

( )( )1000 3361098 Hz

336 30= =

− (3)

(ii) Moving away fcfc u

′ =+

(3)

( )( )1000 336918 Hz

336 30= =

+ (3) (If (i) and (ii) mixed up, award 6 m) Application: Speed traps / speed of stars (red shift) / landing aircraft / ultrasound (blood movement or heartbeat of foetus) ... any one for (3)

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8. Explain the term radioactive decay. (6) Break-up of a nucleus (3) with the release of radiation. (3) Radon-222 is an α-emitter. Write an equation to show the decay of radan-222. (6)

222 218 486 84 2 Rn Po He→ + (... 3 m for each product)

Why is Radon considered to be a health hazard? (5) (As an alpha emitter) dangerous if breathed into lungs / strongly ionising radiation (3) Can cause lung cancer (over a long exposure period). (2) In an experiment to determine the half-life of a short-lived radioactive isotope a measure

of the activity, A, for a sample of the isotope was obtained at various times t. The following results were recorded.

t/s 0 20 40 60 80 100 120 140 160A/Bq 60 45 35 26 20 17 13 10 7

Draw a suitable graph on graph paper to illustrate the change in activity with time and, from the graph determine the half-life of the isotope. (21)

Label axes (3) At least 6 points plotted correctly (3) Curve drawn (3) Good distribution of points (3) Calculation of T1 = 50 s (3) Calculation of T2 = 110 – 50 = 60 s (3) Average T½

= 55 s (3) (Accept value of T½

± 5 s)

20

10

20

30

40

50

60

40 60T1 T2

A / Bq

t / s80 100 120 140 160

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Describe the apparatus which might have been used in this experiment. What reading should be recorded before the radioactive isotope is released? (12) Radioactive source (3) Geiger-Muller tube / detector (3) Counter and stopclock (3) Reading before: background count. (3)

Give two safety precautions which should be observed when handling radioactive materials. Never eat, drink or smoke in the vicinity. (6)

Handle radioactive sources with gloves or tongs. Minimise the time spent using sources of radiation. Make sure sources are properly shielded from you. Keep as far away from the sources as possible. ... any 2 for 2 3 m

9. Defi ne (i) resistance (ii) capacitance. (12) (i) Voltage // R = V/I (3) per unit current / notation (3) (ii) Ratio of charge / C = Q/V (3) to potential / notation. (3) Two resistors are connected in parallel in a circuit. Show that the effective resistance of the

circuit is: 1 2

1 2

R RR R+

(9)

1 2

2 1

1 2

1 2

2 1

1 1 1

1P

P

P

R R RR R

R R RR RR

R R

= +

+=

=+

Outline an experiment to show that a capacitor stores energy. (12) Apparatus: capacitor, cell, bulb / wire (for shorting c) (3) Connect cell to capacitor / charge capacitor (3) Connect bulb across capacitor // short terminals of capacitor (3) Bulb light // spark. (3) Fig. 1 shows a capacitor connected in series to a power supply and a lamp. (i) Explain why the bulb does not light. (6) Current fl ows until capacitor is fully charged (3) Blocks any further current / acts as an insulator. (3) (ii) Suggest a change to the circuit that would light the bulb. Explain your choice. (8) Switch from D.C. → A.C. (4) Capacitor continuously charges and discharges. (4) (iii) What is the charge on the plates when the energy stored is 0.52 mJ? (9) (3) (3) (3)

(3)

(3)

(3)

/E CV Q C21

212 2

= =

2 . . 2 . . 4.89 10Q E C 0 52 10 4 7 102 3 6 9# # #= = =- - -^ ^h h

. 10 7.0 10Q C4 89 9 5# #= =- -

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10. Answer either part (a) or part (b).

(a) Under the guidance of Rutherford, in 1932 Cockcroft and Walton carried out their famous experiment.

(i) Write a nuclear equation for this experiment (9)

7 1 4 43 1 2 2 Li H He He Energy+ → + +

(3) (3) (3) (ii) Explain the signifi cance of this experiment. (5) First artifi cial (2) Splitting of nucleus (3) What is meant by conservation of momentum in nuclear reactions? (6) (Initial) momentum of nucleus = 0 / Initial momentum of nucleus (3) (Final) momentum of products = 0 / Equals fi nal momentum of products (3) Thorium-228 emits an α-particle with a velocity of 4 107ms–1

Write an equation for the reaction. (9)

228 224 490 88 2 Th Ra + He→ (3 m for each part)

Calculate the recoil velocity of the resulting nucleus. (15)

(6)

(3) (3) (3)

(No penalty if minus sign included) Calculate the energy released in the following nuclear reaction.

2 6 4 41 3 2 2 H Li He He Energy+ → + + (12)

Mass of deuteron = 2.014102 a.m.u. Mass of lithium nucleus = 6.015125 a.m.u. Mass of alpha particle = 4.002604 a.m.u. Speed of light = 3 108 ms–1

1 a.m.u. = 1.66 10–27 kg. Mass of reactants = 8.029227 u. (3) Mass of products = 8.005208 u. (3) Decrease in mass = 0.024019 u. / 3.987154 10–29 kg (3) Energy (E = mc2) = 3.6 10–12 J (No extra marks for E = 22.4 MeV) (3) or

(b) What is the function of an induction coil? State the principle on which it is based. Give one application of the induction coil. (12)

Function: Used to get a high voltage (3) from a low voltage d.c. source (such as a battery) (3) Principle: Mutual induction (3) Application: Spark plugs in a car / electric fences / operate a gas discharge tube. (3) Name the Irish physicist who invented the induction coil. (3) (Nicholas) Callan A transformer and an induction coil can both be used to change the size of a voltage.

What is the basic difference in the operation of these two devices? (6) Transformer: AC input / AC output / current fl ows through secondary (3) Induction coil: DC input / (adjusted for) DC output / sparks across gap in secondary. (3)

:PCLM M U M V M V 0Apply Th Th Ra Ra= + =a a

VMM V

RaRa

= a a

2244 4 107#

=^ h

. ms7 14 105 1#= -

Page 13 of 23

Give two factors that affect the effi ciency of a transformer. (6) (I2R) heat losses in coils / eddy currents (in core) / poor fl ux linkage / poor core design /

hysteresis losses / coil resistance. any two 3 + 3 Consider a transformer with a primary coil of 4600 turns and a secondary coil of

240 turns. The input voltage is 230V. Calculate: (i) the output voltage (ii) the output power for a current of 2.4 A (iii) the effi ciency if the input powers is 29.9 W (12)

(i) or P SP P

SS S P

V NV N VV N N⎛ ⎞= =⎜ ⎟⎝ ⎠ (3)

( )240 23012

4600SV V= = (3)

(ii) ( )12 2.4 28.8P VI W= = = (3)

(iii) 28.8 100 96.3%29.9 1

Efficiency = × = (3)

(– 1 for omission or incorrect units) The AC generator is similar to a motor in reverse. Explain this statement. (6) Motor is supplied with current, generates a couple that causes rotation (3) Generator is supplied with rotation, generates a current (3) Draw a labelled diagram of the ac generator (alternator). (11) (Rectangular) coil of wire (3) Poles of a (permanent) magnet (3) (2) slip rings (3) Carbon brushes . (2)

11. (i) Distinguish between heat and temperature. (7) Heat is a form of energy (3) Temperature is a measure of hotness (and coldness). (4)

(ii) Give the equation that defi nes temperature on the Celsius scale. (7) t = T – 273 // 273 k = 0° C (7)

(iii) What is needed to establish a temperature scale? (7) Thermometric property (3) 2 fi xed points and a scale. (4)

(iv) Defi ne specifi c heat capacity. (7) Energy required to raise (the temperature) / (4) of 1kg (of a substance) by 1K / notation (3)

(v) Why are storage heaters surrounded by bricks of high specifi c heat capacity? (7) (Bricks) slowly release / give out (4) their heat. (3)

(vi) Name the three methods of heat transfer. (7) Conduction, Convection, Radiation. all three for 7 m (any two for 4 m)

(vii) Explain how a heat pump works. (7) Pumps energy from a cooler region (4) to a warmer region. (3) (viii) Give a practical application of a heat pump. (7) Refrigerator / Air-conditioning systems . (7)

cm

E33

i=

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12. (a) Defi ne pressure. (6)

Force / FP A= (3) Per unit area / Explain notation. (3) Deep-sea divers can sometimes develop a condition called “the bends” if they rise

back too quickly to the surface of water. Explain briefl y how this condition can arise. (6) (pressure in water) causes too much nitrogen to become dissolved in the blood (3) (on returning to surface), this nitrogen could form bubbles (= bends). (3) The height of mercury in a mercury barometer was 78 cm on a certain day. Given that the density of mercury is 1.36 104 kg m–3 and g = 9.8 m s–2, what was

the atmospheric pressure on that day? (7) P = ρhg = (1.36 × 104)(9.8)(0.78) (4) = 1.04 × 105 Pa (or Nm) (3)

What is a hydrometer and explain how it works. (9) (A hydrometer) measures densities of liquids (3) It consists of a long tube, weighted bulb (at bottom) which fl oats upright (3) When placed in a liquid, it sinks to a value on scale = diversity. (3) (b) Dispersion and total internal refl ection are two phenomena which might occur

when light is passed into a prism. Defi ne the underlined terms. (12) Dispersion: Splitting of light (3) into its (constituent) colours / wavelengths / frequencies. (3) T.i.r: Refl ection of all light back into a dense medium (3) at an interface with a less dense medium (3) (may be answered using a labelled diagram). Prisms are used in binoculars to refl ect light through an angle of 90°. Illustrate how

this occurs. (6)

Use 6 H/m

Calculate the minimum value of the refractive index of the material of the prism for this to occur. (10)

1

sinn

C=

(3) c = 45° (4) n = 1.41 (3) (c) What is the photoelectric effect? (6) Emission of electrons from the surface of a metal. (3) When light of suitable frequency / energy shines on it. (3)

Write down an expression for Einstein’s photoelectric law. (9) hf = Ø + ½ mv2 (each incorrect item ... – 3) 3 × 3

What are X-rays? Who discovered them? (9) What: electromagnetic radiation (3) of short wavelength / high frequency (3) Who: Röntgen (3) Give one reason, why X-rays are considered to be the converse of the photoelectric

effect. (4) For X rays electrons come in and for P.E.E. electrons are emitted / For X rays radiation is produced and for P.E.E. radiation is needed. ... any one for 4 m

Page 15 of 23

(d) State one law of electromagnetic induction. (6) Faraday's law: EMF induced in any closed loop is proportional to (3) the rate at which

the fl ux threading it is changing (3) or

Lenz' law: Direction of induced current (3) opposes change producing it (3) Defi ne magnetic fl ux, Ø. (6) Ø = BA (3) Explain B and A. (3) When a small metal cylinder is dropped through one end of the copper tube as shown in Fig. 2, it falls freely under gravity. If the small cylinder is fi rst magnetised, it then takes much longer to fall through the tube. Explain. (6) Falling magnet induces current / emf in tube (3) Current opposes change i.e slows it down / Lenz' law (3)

A fl at circular coil of radius 0.8 cm and consisting of 40 turns of wire lies in a plane which is perpendicular to a magnetic fi eld of magnetic fl ux density 20 T. Calculate the magnitude of the induced e.m.f. when the fl ux density is steadily reduced to zero in 0.50 s. (10)

2A rπ= (2)

BAE t=

// 20.20 0.016 0.00016π∅ = × × = (3)

20.20 80 0.0160.50

π× × ×=

/ 8 turns 0.013⇒ (3)

0.026 V= // 0.013 0.026 V0.5

= (2)

π

80π

π

Page 16 of 23

ORDINARY LEVEL SECTION A (120 marks)

1. A student carried out an experiment to measure the velocity of an object at various times. The table shows the measurements recorded by the student.

Velocity / ms–1 0.76 1.40 2.08 2.80 3.56 4.24 4.92 5.6

Time / s 0 1.5 3.0 4.5 6.0 7.5 9.0 10.5 (i) Draw a labelled diagram of the apparatus used in the experiment. (9) Trolley (3) Ticker timer and tape / photogate // motion sensor (3) Ramp // connect datalogger to sensor (3) (other posibilities – air track timer, powder track) (ii) Describe how the student measured the velocity. (9) Ticker timer makes 50 dots per second (3) Measure distance for 10 dots (say) (3) Divide by corresponding time (= 0.2s) (3) (iii) Plot a graph, on graph paper, of velocity against time. (12) Label axes (3) First 4 points plotted correctly (3) Last 4 points plotted correctly (3) Straight line of best fi t drawn. (3) (iv) From the graph, fi nd the acceleration of the body. (10) Use the formula y2 – y1 / x2 – x1 (3) Use 2 points from graph (3) Find acceleration = 0.48m/s2 (4) (Ignore incorrect or omission of units)

2. In an experiment to measure the focal length of a concave mirror, an approximate value for the focal length was found fi rst. An object was then placed at various positions, greater than the approximate focal length, in front of the mirror. The following results were obtained:

Object distance u/cm 35 45 55

Image distance r/cm 87 56 46 (i) Why was the object placed at a distance greater than the approximate focal length from the mirror? (4) Real image (4) (ii) Draw a labelled diagram to show how the apparatus might have been arranged in this experiment. Indicate the distances u and v. (12) Object e.g. pin, ray box, crosswires, slit, bulb (fi lament) (3) Concave mirror (3) Screen // pin for no parallax (3) Mark in distances u and v (3) (iii) Using the formula

f u v1 1 1= + or otherwise, fi nd an average value for the focal

length of the mirror. (15) Substitute 1 set of values (3) 1st f value (= 24.96) (3) 2nd f value (= 24.95) (3)

Page 17 of 23

3rd f value (= 25.05) (3) Average (= 24.99 (cm)) (3) (iv) Give one difference between a real image and a virtual image. (6) Real image: Can be formed on a screen // formed by the actual intersection of rays (3) Virtual image: Cannot be formed on a screen // formed by the apparent intersection of rays. (3) (v) What is meant by ‘‘no-parallax’’ between the object and the image. (3) No relative movement between object and image (3)

3. In an experiment to measure the specifi c latent heat of fusion of ice, a student wrote the following: ‘‘Prepare the ice. Take the measurements. Add the ice to the water in the copper calorimeter. When all the ice has melted, take more measurements. Calculate the specifi c latent heat of fusion of ice.’’ (i) Draw a labelled diagram of the apparatus. (9) Labelled diagram to show: Thermometer (3) Calorimeter / beaker (3) Water, ice, insulation, stirrer, balance – only one for (3) Note: no labels, deduct 2 (ii) How might the ice be prepared before it was added to the water? (6) Crush / dry (6) partial answer e.g. ensure the ice was 0oC (3) (iii) What measurements should be taken before adding the ice to the water? (9) mass of calorimeter, mass of water, mass of calorimeter + water, mass of ice, temperature of water, temperature of ice. any three (3 3) (iv) How did the student fi nd the mass of ice? (9) Subtracts // weigh (6) fi nal mass from initial mass // detail (3) (v) Give two precautions to ensure an accurate result in this experiment. (7) Insulation, crush, dry, repeat and take average, use lots of ice, transfer ice quickly, use heated water in calorimeter, large temperature change etc. any two for (4 + 3)

4. A student wished to investigate how the resistance of a thermistor varied with temperature. (i) Draw a labelled diagram of the apparatus used. (12) Labelled diagram to show: thermistor in waterbath (3) thermometer // temperature sensor (3) ohmmeter // datalogger (3) heat source (3) No labels, deduct 2 (ii) The thermistor is not heated in water. Why? Name a more suitable liquid and explain why it is used. (9) Why: Water is a poor conductor of heat (3) Another liquid: Paraffi n (3) Why: Temperature rises uniformly. (3) (iii) How did the student measure the resistance of the thermistor? (3) Ohmmeter (3)

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(iv) The following table shows the values recorded for the resistance and the temperature during the experiment:

Temperature / oC 10 20 30 40 50 60

Resistance / e 10 5.1 4 2.7 1.8 1.2

Using the data in the table, draw a graph on graph paper of the resistance against the temperature. (12) Label axes correctly (3) Plot 3 points correctly (3) Plot another 3 points correctly (3) (smooth) curve (3) (if graph paper not used, max. mark 3 3) (if i on y-axis, max. mark 3 3) (v) Use the graph to estimate the temperature of the thermistor when its resistance is 8 Ω. (4) 11 – 13oC / value consistent with graph (4) partial answer: evidence of using graph. (2)

SECTION B (280 marks)

5. Answer any eight of the following parts (a), (b), (c), etc. (a) Give an example of a scalar and an example of a vector. (7) Scalar: mass, distance, time, etc. any one (3) Vector: force, velocity, acceleration, etc. any one (4) (b) The carriage of a hot-air balloon has an area of 2.5m2. It weighs 300N when it rests on the ground. Calculate the pressure exerted by the carriage on the ground. (7) P = F/A // P = 300/2.5 (4) = 120 (N m–2) (3) (c) Defi ne specifi c heat capacity. (7) Amount of heat (energy) needed to change (3) the temperature (of 1kg of a substance) by 1 Kelvin (4) (d) State one difference between light waves and sound waves. (7) light waves are transverse // sound waves are longitudinal (7) light waves can be polarised // sound waves cannot be polarised (7) light waves travel through vacuum // sound waves cannot travel through vacuum (7) light waves travel (much) faster in air // sound waves travel slower in air (7) light waves are electromagnetic // sound waves are not electromagnetic (7) light waves have a shorter wavelength // sound waves have a longer wavelength (7) valid example e.g. lightning is seen before thunder is heard (7) partial answer e.g. sound travels around corners // incorrect converse. (4) (e) What is noise? (7) Irregular vibrations. (7) (f) Give a use of capacitors. (7) store charge / (radio) tuning / fi ltering / smoothing / timing / coupling / store energy / fl ash camera / phone charger, etc. (7) partial answer e.g. storing electric current. (4) (g) What is a transformer used for? (7) Increase / decrease (4) a voltage. (3)

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(h) What is the refractive index for air and glass? (7) air = 1 (4) glass = 1.5 (3) (i) Draw the symbol for a diode. How does it work? (7) Symbol: (4) only allows current to fl ow in one direction. (3) (j) What is nuclear fi ssion? (7) Break up of nucleus / atom (7) Partial answer e.g. release of energy / neutrons. (4)

6. State Newton’s Universal Law of Gravitation. (9) Force between any two point masses // F = (3) proportional to the product of the masses // Gm1m2/r

2 (3) inversely proportional to the square of the distance between them // explain notation. (3) (i) The acceleration due to gravity at the surface of the earth is given by g = GM/r2. What is meant by the term acceleration due to gravity? (6) acceleration of falling objects (due to earth) // speeding up of following objects // speeding up due to weight // speeding up due to pull of the earth (6) partial answers: defn of acceleration / g/9.8ms–2 / pull of earth / weight. (3) (ii) What do the letters M and r represent in the equation? (6) M = mass of earth (3) r = radius of earth (3) (iii) Why is the acceleration due to gravity on the moon less than the acceleration due to gravity on the earth? (5) Mass of moon is less than mass of earth. (5) (iv) An object of mass 0.5kg is dropped from a height 15 metres above the ground. If the object is initially at rest, calculate: (a) The time which the object will take to reach the ground. (12) s = ut + 1/2at2 (3) 15 = 0 + 1/2(9.8)t2 (3) t2 = 15/4.9 (3) t = 1.7(s) (3) (b) The speed of the object before it hits the ground. (9) v = u + at (3) = 0 + 9.8 (1.7) (3) = 16.66 (ms–1) (3) (c) The kinetic energy of the ball before it hits the ground. (6) KE = 1/2mv2 = 1/2(0.5)(16.66)2 (3) = 69J (3) (v) In reality why is the kinetic energy less than the (initial) potential energy? (3) Energy lost as heat, sound, etc. (3) (Take g = 9.8ms–2)

7. (i) Explain what is meant by the refraction of light and give one example. (9) Bending / changing direction / change of velocity of waves (3) at the boundary / surface / (when waves) travel from one medium to another. (3) Eg: Depth of water appears shallower than it really is / a pen partially immersed in water appears bent, etc. (3) (ii) Describe an experiment to measure the refractive index of a liquid or a solid. (15) Apparatus: (1) Solid – glass block, search pin / (2) Liquid – beaker of water, search pin // (3) Solid – glass block, sheet of paper, search pins / laser. (3)

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Method: (1,2) Draw straight line on a piece of paper and place half of it under glass block / beaker (3) place sheet of paper under glass block and mark its outline. (3) • (1,2) move the search pin until it concides, without parallax, with image of line (3) place 2 pins on one side of block / shine laser on block (3) • (1,2) measure the apparent depth (search pin to top of solid / liquid) and real depth (3) position 2 pins on other side of block in no-parallux with 1st 2 pins. Measure angles i and r. (3) Results: (1,2) Refractive index = real depth / apparent depth (3) Refractive index

sinsin

ri

= (3) (iii) With the aid of a labelled diagram, explain the concept of critical angle. (6) Light goes from more dense less dense medium (3) Angle r = 90o (3) (iv) If the critical angle for glass is 41.8o, calculate a value for its refractive index. (6) n = 1/(sinC) = 1/(sin 41.8o) (3) n = 1.5 (3) (v) What happens when the angle of incidence exceeds the critical angle? Draw a diagram to explain your answer. (10) Total internal refl ection (4) Light goes from more dense less dense medium (3) Light is refl ected back into denser medium. (3) (vi) When light strikes a plane mirror, it becomes refl ected. Give 3 properties of an image formed in a plane mirror. (10) Object distance = image distance Object height = image height Lateral Inversion Virtual image. any three for (4, 3, 3)

8. (i) Name two liquids commonly used in thermometers. (6) Alcohol (3) Mercury. (3) (ii) Give one reason why water is not a suitable liquid in thermometers. (5) Wets the glass Short scale Expands below 4oC etc. any one for (5) (iii) To establish a temperature scale, a thermometric property is needed. What is a thermometric property? Give two examples of a thermometric property. (12) Thermometric property: (physical property that) changes (measurably/continually) (3) with (changing) temperature (3) Examples: resistance / emf / voltage / length / pressure, etc. any two (2 3) (iv) The length of a column of liquid in a uniform glass tube is 2.0cm at the freezing point of water and 27.0cm at the boiling point of water. What will the temperature be when the length of the column is 16.0cm? Give your answer in Kelvins. (12) (l

i – l0/ l100 – l0) 100 = (16 – 2 / 27 – 2) 100 // Label axes of R against T (3)

14/25 100 // Plot points correctly, draw straight line (3) 56oC // Read off value at 16cm = 56oC (3) 329 K (3) (v) There are three types of heat transfer. Name them. (9) Conduction, convection, radiation. (3 3) (vi) What is meant by the U-value of a material? (6) Rate at which heat (3) can be conducted (through a material). (3)

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(vii) If a structure has a low u-value, what does this mean for its insulating ability? (6)

Good insulating ability. (6)

9. (i) What is an electric current? Give its unit. (8) fl ow / movement (3) charge / electrons / electricity (3) unit: amp / ampére. (2) (ii) If too much current fl ows in a plug, it could damage the appliance beyond repair and/or cause electrocution. What safety feature is in the plug to prevent this happening? How does it work? (9) Safety feature: fuse (3) How: thin wire inside fuse melts (when too much current fl ows) (3) cuts off current. (3) (iii) A kettle has a power rating of 2.5kW when connected to the ESB mains voltage of 230V. Calculate the current that fl ows in the kettle. (9) I = P / V (3) = 2500/230 (3) = 10.9(A) (3) (iv) An electric current has a heating effect. Name two other effects of the electric current. (12) Chemical effect (6) Magnetic effect. (6) (v) What is meant by resistance? (6) Voltage // R = V / I (3) per unit curent // explain notation. (3) (vi) The circuit diagram in Fig. 1 shows a 50Ω resistor and a bulb connected in series with a 6V battery. At a certain temperature, the resistance of the bulb is 100Ω. Calculate: (i) The total resistance of the circuit. 150Ω (6) (ii) The current fl owing in the circuit. (12) I = V / R = 6/150 (3) = 0.04(A) (3)

10. (i) Name the sub-atomic particles in an atom. (9) Electron, proton, neutron. (3 3) (ii) Explain the terms: (12) (i) Atomic number Number of protons. (3) (ii) Mass number Number of protons and number of neutrons. (3) (iii) Isotopes Same element (3) different mass number / different number of neutrons (3) (iii) Name the three types of radiation that may be emitted by radioactive nuclei. (9) Alpha (3) Beta (3) Gamma. (3)

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(iv) State which type of radiation is the most ionising and which is the most penetrating. (6) Most ionising: Alpha (3) Most penetrating: Gamma. (3) (v) State a material that could be used to stop the most penetrating radiation. (4) Lead. (4) (vi) ‘‘A certain isotope has a half-life of 300 days.’’ Explain the underlined term. (6) Time taken for half (3) a sample to decay (3) (vii) Describe the equipment needed to measure the half-life of an isotope in the laboratory. (10) (Radioactive) Source (3) Detector e.g. GM tube (4) Counter (and stopclock) (3)

11. Read this passage and answer the questions below. ( . . . ) (i) Give two properties of electrons. (7) Negative, small mass, orbits/outside nucleus, no internal structure, lepton. any two for (4 + 3) (ii) How are X-rays produced? (7) Fast-moving electrons (4) hit a target. (3) (iii) Why does the target in an X-ray tube get very hot? (7) Most of electrons' Kinetic energy (99%) (4) is converted to heat (on hitting the target) (3) (iv) What material is used in the target of the X-ray tube. Why? (7) Tungsten/molybdenum (4) High melting point. (3) (v) Give two uses of X-rays. (7) Photograph bones/internal organs, treat cancer, detect fl aws in materials, determine thickness of materials, etc. any two for (4 + 3) (vi) Name a material that can stop X-rays. (7) Lead. (7) (vii) Calculate the energy of an electron accelerated across a tube of potential 50kV.

(7) E (= Q.V) = 50,000 (1.6 10–9) (4) = 8 10–15(J) (3) (viii) What is the fi nal speed of the electron? (7) KE = 1/2 mv2 // 1/2 (9.11 10–31)v2 = 8 10–15 (4) v = 1.32 108(ms–1) (3) e = 1.6 10–19C m = 9.11 10–31kg

12. Answer any two of the following parts (a), (b), (c), (d). (a) Defi ne: (i) work (ii) power. (12) (i) Product of force (3) and distance (3) (ii) Rate of (3) doing work (3)

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A 15kW crane lifts a mass of 1000kg through a vertical height of 5 metres in 10 seconds. Calculate: (i) the workdone (6) W (= F d) = 1000 9.8 5 (3) = 49,000 (J) (3) (ii) the average power developed (take g = 9.8ms–2) (6) P (= W/t) = 49,000/10 (3) = 4900 W (3) Give one reason why the crane would not be 100% effi cient (4) Energy is lost in heat, sound etc. (4) (b) What is meant by resonance? (6) Transfer of energy between 2 bodies (3) Same natural frequency. (3) What is the relationship between the natural frequency of a string and its length? (6) f & 1/l (6) Name two factors, in addition to length, on which the natural frequency depends. (6) Tension (3) Mass per unit length. (3) Give two characteristics of a musical note. (6) Pitch, loudness, quality. any two for (2 3) Why does the same note played in different instruments sound different? (4) Quality / different no. of harmonics. (4) (c) What is meant by electromagnetic induction? (9) Magnetic fi eld (3) (passing through a coil) changes (3) an emf is induced (in the coil). (3) State Faraday’s law of electromagnetic induction. (9) Size of induced emf (3) proportional to the rate of (3) change of fl ux. (3) Explain how you would use the apparatus shown in Fig. 2 to demonstrate Faraday’s law of electromagnetic induction. (10) Move magnet in/out of coil, needle defl ects (3) Leave magnet inside coil, no defl ection (3) Move magnet faster in/out of coil, bigger defl ection. (4) (d) What is a semi-conductor? (6) Conductivity/resistivity lies between (3) a (good) conductor and a (good) insulator. (3) What are the two types of charge carriers in semi-conductors? (6) electrons (3) (positive) holes. (3) What is meant by the term ‘‘doping’’? (6) adding (suitable) impurities (to improve conductivity). (6) Explain the difference between n-type and p-type semi-conductors. (10) n-type: material with spare electrons/conducts mainly by electron fl ow (5) p-type: material with spare holes/conducts mainly by hole fl ow. (5)