HSC PHYSICS NOTES Collins Module 3

Travelled in straight linesShadowsCould pass through thin metal foils

Some characteristics fitted the wave model:

They left the cathode at right angles to the surfaceObviously deflected by magnetic fieldsSmall paddlewheels turned when placed in path of raysTravelled slower than light

Some fitted the particle model

When Thompson was able to observe deflection via electric field, he confirmed the charged particle theory

1.1 explain why the apparent inconsistent behaviour of cathode rays caused debate as to whether they were charged particles or electromagnetic waves

At very low pressure, air conducts electricityIf a significantly high potential difference is placed over a cathode ray tube, electricity flows as a stream of charged particles

1.2 explain that cathode ray tubes allowed the manipulation of a stream of charged particles

Moving charged particles in a magnetic field experience a force1.3 identify that moving charged particles in a magnetic field experience a force

Charged plates produce an electric field1.4 identify that charged plates produce an electric field

Right hand palm rule gives directionFormula gives magnitude ( is angle to magnetic field)

1.5 describe quantitatively the force acting on a charge moving through a magnetic field

Field lines go towards negativeBulge near edges

1.6 discuss qualitatively the electric field strength due to a point charge, positive and negative charges, and oppositely charged parallel plates

1.7 describe quantitatively the electric field due to oppositely charged parallel plates

By applying a magnetic and electric field to electrons, and equating the equations once balanced, q/m could be calculated

Cathode rays pass through slots in cylinders making a near parallel beamElectric field deflects beam downwards, magnetic field deflects beam upwardsWhen balanced, two equations can be equated

1.8 outline Thomson's experiment to measure the charge/mass ratio of an electron

1. Increased understandings of cathode rays led to the development of televisionSaturday, 23 October 20109:47 AM

9.4 From Ideas to Implementation Page 23

1.9 outline the role of:- electrodes in the electron gun- the deflection plates or coils- the fluorescent screenIn the cathode ray tube of conventional TV displays and oscilloscopes

Electrodes control 'brightness' of beam, focus the beam and accelerate electrons along the tube

The deflection plates deflect the beam of electrons separately up, down, left, rightThe screen emits light when electrons strike it

Coloured 'streamers' appear and both the anode and cathode are surrounded by a luminous glow

As pressure is reduced further, positive glow extends up tube for about half its lengthIf pressure is reduced further, positive column breaks into a series of striationsAt Very low pressures, a green glow appears in the glass at the end of the discharge tube opposite the cathode

1.10 perform an investigation and gather first-hand information to observe the occurrence of different striation patterns for different pressures in discharge tubes

1.11 perform an investigation to demonstrate and identify properties of cathode rays using discharge tubes:


discharge tubes: containing a Maltese cross containing electric plates with a fluorescent display screen containing a glass wheel analyse the information gathered to determine the sign of the charge on cathode rays

Deflected towards the positive plate in the electric plates experiment, therefore, negatively charged

1.12 solve problem and analyse information using: and


Set up an induction coil connected to a ring with a spark gap, and a second ringWhen voltage applied, spark appeared in both ringsIf UV light shone onto gap, more sparking occurred at detecting loopGlass shielded spark and no spark produced at receiving coil

2.1 describe Hertzs observation of the effect of a radio wave on a receiver and the photoelectric effect he produced but failed to investigate

First calculated frequency from LC circuit (inductor L and capacitor C)Used interference patterns to figure out wavelength: set up metal plate for radio waves to deflect off such that some went from source to receiver and some bounced off plate. Using interference pattern, calculated wavelength

Velocity very close to predicted value by Maxwell

2.2 outline qualitatively Hertzs experiments in measuring the speed of radio waves and how they relate to light waves

Black body - perfect emitter or absorber of energyPlanck proposed energy released from black body in quanta i.e. frequency is proportional to energy. Set amount of energy goes into the black body, and the same amount comes out, in discrete packets, proportional to the amount of energy

2.3 identify Plancks hypothesis that radiation emitted and absorbed by the walls of a black body cavity is quantised

Einstein proposed all electromagnetic radiation occurred in discrete quanta, which he called photons (particle theory of light)

Proposed that EM interacted with matterEssentially, extended on Planck's mathematical relationship

2.4 identify Einsteins contribution to quantum theory and its relation to black body radiation

Photoelectric effect is the emission of electrons from substances, in particular metals, when they are bombarded with light

2.5 explain the particle model of light in terms of photons with particular energy and frequency

The greater the energy of the photoelectrons, the greater voltage needed to stop them

2. The reconceptualization of the model of light led to an understanding of the photoelectric effect and black body radiationSunday, 13 March 201110:33 AM


The greater the energy of the photoelectrons, the greater voltage needed to stop them (known as stopping voltage)

As frequency is proportional to energy, higher frequency means more kinetic energyWork function of a metal is how much energy is required for electrons to reach the surface and be emitted from the metal (i.e. there is a threshold frequency)

Higher intensity means more current

2.6 identify the relationships between photon energy, frequency, speed of light and wavelength: and

Set up an induction coil so that it generates sparksTune in a radio receiverObserve radio interference on FM and AM (more on AM)

2.7 perform an investigation to demonstrate the production and reception of radio waves

2.8 identify data sources, gather, process and analyse information and use available evidence to assess Einsteins contribution to quantum theory and its relation to black body radiation

Cathode coted with photosensitive materialPhotoelectrons accelerated to the anode by potential differencePhotocurrent proportional to amount of light that falls on them (e.g. radiation detectors, light meters, electric 'eyes')

2.9 identify data sources, gather, process and present information to summarise the use of the photoelectric effect in photocells

2.10 solve problems and analyse information using: and

Planck worked for Nazi partyPlanck saw no moral imperative to oppose the Nazi regime until all Jewish teachers were sacked from German Universities

Planck spoke out against anti-Semitism directed towards EinsteinPlanck - anti-Nazi views, refused to work on war researchEinstein was a pacifistWhen Hitler came to power, he toured Europe making speeches about the NazisMoved to US, advocated re-armament of democratic government to oppose the Nazi tyrannyWarned Roosevelt of potential for German atomic bomb - led to Manhattan ProjectAdvocated for a world government to eliminate the threat of atomic war

2.11 process information to discuss Einsteins and Plancks differing views about whether science research is removed from social and political forces


Conductance in metals is due to electron 'cloud' of shared electrons between atoms able to move freely

3.1 identify that some electrons in solids are shared between atoms and move freely

3.2 describe the difference between conductors, insulators and semiconductors in terms of band structures and relative electrical resistance

Conductor has lowest resistance, semiconductor has medium and insulator has high.Conductors resistance decreases with temperature decrease, semiconductors decrease with temp. increase

Absence of electrons in a nearly full band is a 'positive hole' Current is the flow of charge - i.e. electrons and positive holes

3.3 identify absences of electrons in a nearly full band as holes, and recognise that both electrons and holes help to carry current

Conductors - large amount of free electronsSemi-conductor - someInsulator - almost none

3.4 compare qualitatively the relative number of free electrons that can drift from atom to atom in conductors, semiconductors and insulators

Silicon is more abundant (and hence cheaper)Silicon retains semi-conducting properties at higher temperatureSilicon forms insulating layer when heated to high temperatures (used in integrated circuits)Germanium was originally used due to the lack of refinement processes of silicon.

3.5 identify that the use of germanium in early transistors is related to lack of ability to produce other materials of suitable purity

Adding a small amount of a group three element into silicon (a group four element) will increase the amount of positive holes as the fourth bond of silicon is incomplete (p-type)

Adding a small amount of a group five element into silicon will increase the amount of negative electrons (n-type)

3.6 describe how doping a semiconductor can change its electrical properties

In a p-type material positive holes are the majority carriers and electrons are minority carriersIn an n-type material electrons are the majority carriers and positive holes are minority carriers

3.7 identify differences in p and n-type semiconductors in terms of the relative number of negative charge carriers and positive holes

Thermionic devices are bigger which limited the minimum size of any electronic device (miniaturisation is essential to progress of electronics)

3.8 describe differences between solid state and thermionic devices and discuss why solid state devices replaced thermionic devices

3. Limitations of past technologies and increased research into the structure of the atom resulted in the invention of transistorsSunday, 13 March 201110:34 AM


(miniaturisation is essential to progress of electronics)Thermionic devices consume more electrical energy and produce more heat (i.e. much more inefficient)

Thermionic devices are much more fragileCannot operate as fast as SSDsRequire a 'warm-up' time to become operational whilst the heating filament warms

Students in chairs - standing up means conduction band, sitting means valance bandRemove a student - positive hole is created, students (electrons) shift down, whereas hole moves up the row

3.9 perform an investigation to model the behaviour of semiconductors, including the creation of a hole or positive charge on the atom that has lost the electron and the movement of electrons and holes in opposite directions when an electric field is applied across the semiconductor

A p-n junction acts as a diode (i.e. charge can only flow in one direction), as application of a charge will move electrons from n type into p-type, and vice versa, increasing 'depletion zone' and resisting charge flow

Semiconductors replaced triodes as a transistor, for example, amplificationDevelopment of transistor allowed for miniaturisation of electronic components, efficiency increased, communication technologies made much more efficient

3.10 gather, process and present secondary information to discuss how shortcomings in available communication technology lead to an increased knowledge of the properties of materials with particular reference to the invention of the transistor

Miniaturisation and mass production of electronics -More e-wasteDigital revolutionLess paper neededInformation easily accessibleInterconnected societyAutomation of processes - job loss/better quality of life

3.11 identify data sources, gather, process, analyse information and use available evidence to assess the impact of the invention of transistors on society with particular reference to their use in microchips and microprocessors

Incident light hits semiconductorElectron/positive hole pair produced via photo-ionisationPotential barrier (p-n type junction) separates these charges, setting up an emfMetal contacts conduct away electronsPass through the load and move back to the p-type silicon doing useful work

3.12 identify data sources, gather, process and present information to summarise the effect of light on semiconductors in solar cells


Short wavelength X-rays produced by hitting metal target with electrons (e.g. in an induction coil)

Penetrate and reflect from atomic planes of metal crystalIn some directions constructive interference would occur, in others, destructivex-rays hit screen and results analysed using formula

4.1 outline the methods used by the Braggs to determine crystal structure

Metals possess a crystal lattice structure4.2 identify that metals possess a crystal lattice structure

Conduction in metals is the free movement of electrons unimpeded by the lattice4.3 describe conduction in metals as a free movement of electrons unimpeded by the lattice

Resistance in metals is proportional to presence of impurities and scattering of electrons by lattice vibration

4.4 identify that resistance in metals is increased by the presence of impurities and scattering of electrons by lattice vibrations

Superconductivity is due to a population of electron pairs unaffected by electrical resistance as described in the BCS theory

4.5 describe the occurrence in superconductors below their critical temperature of a population of electron pairs unaffected by electrical resistance

Below the critical temperature, lattice vibrations decrease to a point where electrons do not collide with the lattice, and pass unimpeded through

Electron pulls down on positively charged lattice, distorting itDistortion attracts another electron, 'pairing' the twoThis is known as a Cooper pair, which pass unimpeded through the latticeCooper pairs result in superconductivity

4.6 discuss the BCS theory

Superconductors minimise energy loss due to resistive heating and to allow the generation of intense magnetic fields

Limitations - require incredibly low temperatures

Brittle'high temperature' superconductors which can work if cooled with liquid nitrogen are:

4.7 discuss the advantages of using superconductors and identify limitations to their use

4. Investigations into the electrical properties of particular metals at different temperatures led to the identification of superconductivity and the exploration of possible applicationsSunday, 13 March 201110:34 AM


BrittleDifficult to manufactureDifficult to form into cablesChemically unstable in some environments

YBa2Cu3O7 - critical temp: 92 KHg - critical temp: 4.2 KNiobium Germanium compounds - critical temp: 23.2 K

4.8 process information to identify some of the metals, metal alloys and compounds that have been identified as exhibiting the property of superconductivity and their critical temperatures

Superconducting ceramic disc with small permanent magnet placed on top4.9 perform an investigation to demonstrate magnetic levitation

A superconductor does not allow a magnetic field to penetrate its interior(field inside induces a current that produces a magnetic field that just balances out the field the would have penetrated the substance)

This is known as the Meissner effect

4.10 analyse information to explain why a magnet is able to hover above a superconducting material that has reached the temperature at which it is superconducting

Levitation: maglev train in Japan: Helium cooled superconducting magnets on the vehicle interact with coils in the guideway in such a way that repulsion between 'like poles' causes the train to lift off the guideway

Train 'chases' changing magnetic field on track ahead, and is repelled from behind

4.11 gather and process information to describe how superconductors and the effects of magnetic fields have been applied to develop a maglev train

Computers - faster information processingGenerators and motors - more efficientTransmission of electricity - DC based, more efficient, less energy loss

4.12 process information to discuss possible applications of superconductivity and the effects of those applications on computers, generators and motors and transmission of electricity through power grids


Force on a charge moving through a magnetic field:

Electric field strength between two parallel plates:

Force on a charge in an electric field:

Relationship between photon energy and frequency:

Relationship between frequency and wavelength of a photon:

FormulasSunday, 13 March 201110:35 AM


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HSC PHYSICS NOTES Collins Module 3