Numbers
Edexcel A-Level Physics 9PH0
Working as a Physicist
Topic overviewSI base units, derived units and homogeneityUnit prefixes, conversion and order-of-magnitude estimatesResolution, random errors and systematic errorsUncertainty and how uncertainties combineImproving measurements, graphs and evaluating resultsPeer review, publication and scientific integrityRisk, benefit and the role of science in society
Mechanics
Topic overviewThe equations of uniformly accelerated motionDisplacement-time and velocity-time graphsScalars and vectorsResolving vectors and finding resultantsProjectile motionFree-body diagrams and Newton's first and second lawsNewton's third law, mass and weightTerminal velocity and measuring g by free fallLinear momentum and its conservationElastic and inelastic collisions in one dimensionThe moment of a forceCentre of gravity, equilibrium and the principle of momentsWork done by a forceKinetic and gravitational potential energyConservation of energy and dissipationPower, and the equation P = FvEfficiency and wasted energy
Electric Circuits
Topic overviewCurrent, charge and potential differenceResistance, Ohm's law and ohmic behaviourElectrical power and energyKirchhoff's laws: the current and potential difference rulesCombining resistances in series and parallelCircuit calculations, meters and component failureI-V characteristics of conductors, lamps and diodesThermistors, light dependent resistors and resistance changeResistivity and determining it experimentallyCharge carriers, drift velocity and I = nqvAThe potential divider equation and the loading effectSensing circuits with thermistors and light dependent resistorsElectromotive force, internal resistance and lost voltsMeasuring e.m.f. and internal resistance, and cells in combination
Materials
Topic overviewDensity and how it is measuredUpthrust and Archimedes' principleFloating, sinking and upthrust calculationsViscosity, laminar flow and Stokes' lawTerminal velocity of a sphere falling through a liquidMeasuring viscosity by the falling-ball methodHooke's law, stress and strainThe Young modulus and calculations with itDetermining the Young modulus of a wireForce-extension graphs, elastic and plastic deformationStress-strain graphs, ductile and brittle materialsElastic strain energy
Waves and Particle Nature of Light
Topic overviewDescribing a progressive waveThe wave equation and its useLongitudinal and transverse wavesDisplacement-distance and displacement-time graphsMeasuring the speed of sound with an oscilloscopeWavefronts, superposition and phaseCoherence, path difference and phase differenceInterference in practiceStationary waves, nodes and antinodesHarmonics on a stretched stringInvestigating a vibrating string, and air columnsIntensity, the inverse square law and refractive indexRefraction, wave speed and the critical angleTotal internal reflection and measuring refractive indexLenses, ray diagrams and the images they formLens power and the thin lens equationLens calculations and magnificationReflection, transmission and the pulse-echo principlePulse-echo calculations, resolution and ultrasoundPolarisation and diffractionSingle-slit patterns and the diffraction grating equationGrating spectra and measuring wavelengthElectron diffraction and the de Broglie equationde Broglie calculations and wave-particle dualityPhotons and photon energyModels of light and the electronvoltLine spectra and atomic energy levelsThe photoelectric effect and Einstein's equationEvidence for the photon model and photoelectric calculations
Further Mechanics
Topic overviewImpulse and force-time graphsConservation of momentum in two dimensionsInvestigating momentum and analysing collisions on videoElastic and inelastic collisionsKinetic energy, momentum and collision calculationsThe radian, angular displacement and angular velocityAngular velocity, period and frequency of rotationCentripetal accelerationCentripetal force and what provides itVertical loops and centripetal force calculations
Electric and Magnetic Fields
Topic overviewElectric fields and electric field strengthField strength calculations and field diagramsCoulomb's law and the field of a point chargeInverse-square behaviour and combining fieldsElectric potential and field strength as a potential gradientUniform fields between parallel plates, and the potential near a point chargeEquipotentials, field diagrams and work doneCapacitance and the energy stored in a capacitorCapacitor charge and energy calculationsCharging and discharging graphs and the time constantThe exponential decay equations and logarithmic graphsInvestigating capacitor discharge and time-constant calculationsMagnetic flux density, flux and flux linkageForces on currents and moving chargesThe conditions for inducing an e.m.f.Faraday's law and Lenz's lawFlux linkage graphs and induced e.m.f. calculationsAlternating current, peak and r.m.s. valuesOscilloscope traces and alternating current calculations
Nuclear and Particle Physics
Topic overviewNuclide notation, isotopes and the alpha scattering experimentConclusions from alpha scattering and the changing model of the atomThermionic emission and linear acceleratorsThe cyclotron and the radius of a charged particle's pathParticle tracks, conservation laws and why high energies are neededMass-energy equivalence, pair production and annihilationParticle energy units and relativistic lifetimesBaryons, mesons, leptons and quark compositionThe six quarks, antiparticles and fundamental particlesConservation of charge, baryon number and lepton numberQuark changes in beta decay and testing particle equations
Thermodynamics
Topic overviewSpecific heat capacity and specific latent heatMeasuring specific heat capacity and calibrating a thermistorMeasuring specific latent heatInternal energy, temperature and absolute zeroMean kinetic energy and the absolute temperature scaleThe kinetic theory equation and its derivationThe ideal gas equation and molecular kinetic energyBoyle's law and investigating a fixed mass of gasBlack body radiation and Wien's lawThe Stefan-Boltzmann law and stellar calculations
Space
Nuclear Radiation
Topic overviewMass deficit, binding energy and the atomic mass unitBinding energy per nucleon, fission and fusionBackground radiation and the three types of nuclear radiationIonising power, penetration and changes in the nucleusNuclear equations and investigating gamma absorptionActivity, the decay constant and half-lifeDecay graphs and half-life calculations
Gravitational Fields
Oscillations
Topic overviewThe conditions for simple harmonic motionDisplacement, velocity and acceleration in simple harmonic motionThe mass-spring oscillator and the simple pendulumDisplacement, velocity and acceleration graphsReading period, amplitude and speed from oscillation graphsEnergy in an undamped oscillationDamping and where the energy goesFree and forced oscillations and resonanceResonance in practice and determining an unknown mass
Waves and Particle Nature of Light
- 29 subtopics
- 46 things to know
- Papers 2 and 3
What Waves and Particle Nature of Light covers
The largest topic on Paper 2 and the one that carries the course from classical waves to quantum behaviour: wave properties and the wave equation, superposition, stationary waves, refraction and total internal reflection, lenses, polarisation and diffraction, and then de Broglie, photons, line spectra and the photoelectric effect.
Where it is assessed
Papers 2 and 3
Advanced Physics II, then the general and practical principles paper.
Check the Pearson Edexcel specification ↗The 29 subtopics
Each one has its own page.
- Describing a progressive waveRecall questions on amplitude, wavelength, frequency and period, why amplitude is not the peak-to-peak value, and how energy carried depends on amplitude.Open →
- The wave equation and its useRecall questions on v = fλ and where it comes from, and on what happens to speed, frequency and wavelength when a wave crosses into a new medium.Open →
- Longitudinal and transverse wavesRecall questions on the difference between the two, examples of each, compressions and rarefactions, and why sound cannot travel through a vacuum.Open →
- Displacement-distance and displacement-time graphsRecall questions on what each axis shows, telling the two graphs apart, how a longitudinal wave is drawn, and identifying nodes and antinodes.Open →
- Measuring the speed of sound with an oscilloscopeRecall questions on the signal generator and microphone arrangement, why a two-beam oscilloscope is used, the y-gain and time base, and the main uncertainties.Open →
- Wavefronts, superposition and phaseRecall questions on what a wavefront is, how wavefronts relate to wavelength, the principle of superposition, and what it means for oscillations to be in phase.Open →
- Coherence, path difference and phase differenceRecall questions on coherence and why it is needed, why two filament lamps will not interfere, and the relationship between path and phase difference.Open →
- Interference in practiceRecall questions on the path and phase conditions for constructive and destructive interference, the two-loudspeaker experiment, and whether interference destroys energy.Open →
- Stationary waves, nodes and antinodesRecall questions on how a stationary wave forms, node and antinode spacing, the phases either side of a node, and the three ways it differs from a progressive wave.Open →
- Harmonics on a stretched stringRecall questions on why only certain frequencies fit, the wavelength and frequency of the nth harmonic, and how tension, length and mass per unit length change the first harmonic.Open →
- Investigating a vibrating string, and air columnsRecall questions on the graphs that confirm the frequency dependences, measuring mass per unit length, locating resonance precisely, and stationary waves in a closed tube.Open →
- Intensity, the inverse square law and refractive indexRecall questions on the definition and unit of intensity, why it falls as an inverse square, how it depends on amplitude, and the definition of refractive index.Open →
- Refraction, wave speed and the critical angleRecall questions on the refraction relationship, which way a ray bends and why, the speed and wavelength in the medium, and the definition of the critical angle.Open →
- Total internal reflection and measuring refractive indexRecall questions on the two conditions for total internal reflection, sin C = 1/n, and the glass-block experiment with optical pins.Open →
- Lenses, ray diagrams and the images they formRecall questions on focal length and the principal axis, the three construction rays, real against virtual images, and the image formed at each object position.Open →
- Lens power and the thin lens equationRecall questions on power in dioptres, the sign of a diverging lens, why the powers of thin lenses in contact add, and the real-is-positive convention.Open →
- Lens calculations and magnificationRecall questions on solving the thin lens equation for converging and diverging lenses, the two expressions for magnification, and what covering half a lens does.Open →
- Reflection, transmission and the pulse-echo principleRecall questions on what happens at a boundary, why coupling gel is used, and the relationship a pulse-echo system uses to find a distance.Open →
- Pulse-echo calculations, resolution and ultrasoundRecall questions on halving the measured time, why an object smaller than the wavelength is invisible, pulse length and resolution, and why the gap between pulses matters.Open →
- Polarisation and diffractionRecall questions on plane polarisation and what it shows about light and sound, polarising filters and glare, and the conditions under which diffraction is most pronounced.Open →
- Single-slit patterns and the diffraction grating equationRecall questions on Huygens' construction, the single-slit pattern and how it changes with wavelength, and the grating equation with its slit spacing.Open →
- Grating spectra and measuring wavelengthRecall questions on why grating maxima are sharper than double-slit fringes, the white-light spectrum and how it differs from a prism's, and the laser experiment.Open →
- Electron diffraction and the de Broglie equationRecall questions on the electron diffraction arrangement, why rings rather than spots are seen, and the de Broglie equation with the Planck constant.Open →
- de Broglie calculations and wave-particle dualityRecall questions on finding a de Broglie wavelength from speed or accelerating voltage, why a cricket ball shows no diffraction, and why an electron is not simply a wave.Open →
- Photons and photon energyRecall questions on what a photon is, E = hf and its wavelength form, which observations the wave model explains, and which need photons.Open →
- Models of light and the electronvoltRecall questions on Newton, Huygens, Young and Einstein, the fundamental conflict between the two models, and the electronvolt and its value in joules.Open →
- Line spectra and atomic energy levelsRecall questions on emission and absorption spectra, why every element has its own lines, transitions and photon frequency, and why energy levels are negative.Open →
- The photoelectric effect and Einstein's equationRecall questions on threshold frequency and work function, Einstein's equation, why the maximum kinetic energy appears in it, and what happens below threshold.Open →
- Evidence for the photon model and photoelectric calculationsRecall questions on the three features the wave model cannot explain, the gold-leaf demonstration, and the kinetic energy against frequency graph.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
What is the wave equation, and how are the frequency and period of a wave related?
Key term
Two sound waves have the same frequency but different amplitudes. What physical difference does this make?
Numbers
Where do the compressions of a sound wave lie on a displacement graph, and how do you tell a displacement-distance graph from a displacement-time one?
Evaluation
How can the uncertainty in the wavelength measurement be reduced in the speed of sound experiment?
Evaluation
What are the main sources of uncertainty in the speed of sound determination, and how is an antinode identified on a displacement graph?
Key term
What are two examples of longitudinal waves?
Key term
What are two examples of transverse waves?
Key term
What is meant by the phase of an oscillation and by coherence, and must coherent sources have equal amplitudes?
Numbers
What is path difference, how is it related to phase difference, and why can two filament lamps not produce interference?
Numbers
What are the interference conditions expressed as phase differences, and what happens if one of two loudspeakers is turned down?
Key term
Does destructive interference destroy energy?
Numbers
What does μ represent, and what are the wavelength and frequency of the nth harmonic on a string of length L?
Process
What happens to the first harmonic frequency of a string if the mass per unit length is quadrupled, if the vibrating length is halved, and if the tension is quadrupled?
Numbers
What are the wavelength and frequency of the second harmonic, and which graph confirms how frequency depends on tension?
Numbers
What is the separation of two adjacent nodes?
Key term
Which length must be measured when investigating a vibrating string, and why?
Numbers
What is meant by the intensity of radiation, what is its equation and unit, and why does it fall off as an inverse square?
Numbers
How is the refractive index of a rectangular glass block measured, and how is it obtained from the readings?
Evaluation
Why is a graph plotted rather than separate values averaged, and why should the optical pins be placed as far apart as possible?
Key term
Does the frequency of light change when it is refracted?
Process
How does the intensity of a wave depend on its amplitude?
Key term
What are the paths of the three standard construction rays used to locate an image formed by a converging lens?
Process
What happens when the object is placed at the principal focus of a converging lens?
Numbers
What is the equation for the power of a lens, its unit, and the sign of a diverging lens's power?
Process
Where is the image formed by a diverging lens, and what happens when an object is placed at the principal focus of a converging lens?
Numbers
What is the real-is-positive sign convention, and where is the image of an object 0.30 m from a converging lens of focal length 0.20 m, and from a diverging lens of focal length −0.20 m?
Numbers
What does a magnification of less than 1 tell you about the image?
Evaluation
What happens if a scanner assumes a wave speed higher than the true speed in tissue, why do scans of shallow structures use higher frequencies, and what is the disadvantage of an extremely short pulse?
Numbers
Why can a pulse-echo system not detect an object smaller than the wavelength, how does reflection at a fixed end differ from reflection at a free end, and what decides how much is reflected?
Key term
What is plane polarisation, and what does it tell you that light can be polarised but sound cannot?
Process
What is unpolarised light, when is diffraction at a gap most pronounced, and how does a single-slit pattern change with blue light?
Numbers
Why can you hear someone talking round the corner of a doorway but not see them?
Numbers
How does the order of the colours in a grating spectrum compare with that produced by a prism?
Process
Why is it wrong to call an electron simply a wave, and how would you shorten the electrons' wavelength in a microscope?
Numbers
Which observations show the wave nature of electrons and which the particle nature, and how does de Broglie wavelength change with speed?
Numbers
What pattern does electron diffraction produce, why is graphite used to diffract electrons, what is the Planck constant, and how does h/p reduce to a length?
Numbers
How is the frequency of the radiation emitted related to an electron transition between two energy levels?
Numbers
Which properties of electromagnetic radiation does the wave model explain, and which can only be explained by photons?
Numbers
Why is the electronvolt convenient in atomic physics, and in what way does the photon model conflict with the wave model?
Process
What happens to the energy of a photon if its wavelength is halved?
Numbers
Why does Einstein's equation refer to the maximum kinetic energy, and what is observed below the threshold frequency however intense the radiation?
Key term
What is the work function of a metal, what does raising the intensity above threshold do, and why does a positively charged electroscope not discharge?
Process
How can the photoelectric effect be demonstrated with a gold-leaf electroscope?
Process
In the gold-leaf electroscope demonstration of the photoelectric effect, why does the leaf not fall if the electroscope is charged positively?
Process
Light of wavelength 4.00 × 10⁻⁷ m falls on sodium, whose work function is 3.68 × 10⁻¹⁹ J. What is the maximum kinetic energy of the photoelectrons?
Take Waves and Particle Nature of Light further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Progressive wave vs Stationary wave
Progressive wave: disturbance transferring energy through space. Stationary wave: fixed pattern formed by opposite superposed waves.
Refraction vs Diffraction
Refraction: direction change caused by wave-speed change. Diffraction: spreading when waves pass an aperture or edge.
Photon vs Photoelectron
Photon: discrete quantum of electromagnetic energy. Photoelectron: electron emitted after absorbing sufficient radiation.
Questions from this topic
Each one with the model answer underneath.
- 1
What is a progressive wave?
Model answer
It is a disturbance that travels through space or a medium, transferring energy from one place to another without any net transfer of matter.
- 2
How is the amplitude of a wave defined?
Model answer
The amplitude is the maximum displacement of a point on the wave from its equilibrium position.
- 3
Why is the amplitude not the same as the peak-to-peak displacement shown on a trace?
Model answer
The peak-to-peak displacement runs from a crest right down to a trough, so it is twice the amplitude.
- 4
What is meant by the wavelength of a wave?
Model answer
The wavelength is the shortest distance between two points on the wave that are oscillating in phase, such as one crest and the next.
- 5
How is the frequency of a wave defined, and what is its unit?
Model answer
Frequency is the number of complete oscillations passing a point each second, measured in hertz (Hz).
- 6
What is meant by the period of a wave?
Model answer
The period is the time taken for one complete oscillation of a point on the wave.
What is inside Levo
Six ways to work the same material.
Waves and Particle Nature of Light revision questions
- What does Waves and Particle Nature of Light cover in Edexcel A-Level Physics?
- 29 subtopics: describing a progressive wave, the wave equation and its use, longitudinal and transverse waves, displacement-distance and displacement-time graphs, measuring the speed of sound with an oscilloscope, wavefronts, superposition and phase, coherence, path difference and phase difference, interference in practice, stationary waves, nodes and antinodes, harmonics on a stretched string, investigating a vibrating string, and air columns, intensity, the inverse square law and refractive index, refraction, wave speed and the critical angle, total internal reflection and measuring refractive index, lenses, ray diagrams and the images they form, lens power and the thin lens equation, lens calculations and magnification, reflection, transmission and the pulse-echo principle, pulse-echo calculations, resolution and ultrasound, polarisation and diffraction, single-slit patterns and the diffraction grating equation, grating spectra and measuring wavelength, electron diffraction and the de broglie equation, de broglie calculations and wave-particle duality, photons and photon energy, models of light and the electronvolt, line spectra and atomic energy levels, the photoelectric effect and einstein's equation and evidence for the photon model and photoelectric calculations. Each one has its own page with questions and model answers.
- How is Waves and Particle Nature of Light organised?
- By the Edexcel 9PH0 specification, subtopic by subtopic, so it matches the order you are taught it in.
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