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
Space
- 7 subtopics
- 12 things to know
- Papers 2 and 3
What Space covers
Paper 2 content on measuring the universe: luminosity and the inverse square law, parallax and standard candles, the Hertzsprung-Russell diagram and stellar life cycles, and the Doppler effect, Hubble's law and what dark matter does to the predicted fate of the universe.
Where it is assessed
Papers 2 and 3
Advanced Physics II, then the general and practical principles paper.
Check the Pearson Edexcel specification ↗The 7 subtopics
Each one has its own page.
- Luminosity, intensity and the inverse square lawRecall questions on the difference between luminosity and received intensity, the equation linking them, why 4πd² appears, and the assumptions the equation makes.Open →
- Trigonometric parallax and standard candlesRecall questions on the parallax method and its range limit, the astronomical unit and the parsec, what a standard candle is, and why intervening dust distorts a distance.Open →
- The Hertzsprung-Russell diagramRecall questions on what the two axes show and why they are unusual, where the main sequence, red giants and white dwarfs lie, and what fixes a star's position along the main sequence.Open →
- The life cycle of starsRecall questions on the energy source of a main-sequence star, what keeps it stable, how a Sun-like star moves off the sequence, and why the most massive stars are the shortest lived.Open →
- The Doppler effect and redshiftRecall questions on the Doppler effect, the definition of redshift and the equations for it, when z ≈ v/c holds, and what a blueshift would mean.Open →
- Hubble's law and the age of the universeRecall questions on the statement of Hubble's law and its constant, why universal recession does not put us at the centre, and estimating the age of the universe from 1/H₀.Open →
- Dark matter and the fate of the universeRecall questions on what dark matter is and the evidence for it, the critical density, how mean density decides the fate, and what distant supernovae revealed.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
Why does the distance appear as 4πd² in the intensity relationship, and what happens to the intensity if the distance is trebled?
Numbers
What is an astronomical unit, and how is a star's distance found from its luminosity and the intensity received?
Key term
Which two types of object are commonly used as standard candles?
Key term
In what units is luminosity shown on a Hertzsprung-Russell diagram, why is that axis logarithmic, and where do red giants lie?
Process
Where do white dwarfs and the Sun sit on the Hertzsprung-Russell diagram, and what fixes a star's position along the main sequence?
Process
What is the energy source of a main-sequence star, what keeps it stable, and where does a Sun-like star end up?
Numbers
Two stars have the same luminosity but different surface temperatures. How do their sizes compare?
Numbers
What is meant by the redshift of a galaxy, and for light does it matter whether the source or the observer is moving?
Numbers
What is the SI unit of the Hubble constant, and what does Hubble's law tell us about the universe?
Key term
What does it mean if a galaxy shows a blueshift instead?
Evaluation
How is the Hubble constant used to estimate the age of the universe, and why do dark matter and its uncertainty obscure that?
Take Space further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Luminosity vs Flux
Luminosity: total power emitted by a star. Flux: power received per unit area.
Red shift vs Blue shift
Red shift: observed wavelength increased by recession. Blue shift: observed wavelength decreased by approach.
Apparent magnitude vs Absolute magnitude
Apparent magnitude: brightness scale observed from Earth. Absolute magnitude: brightness scale at a standard distance.
Questions from this topic
Each one with the model answer underneath.
- 1
What is meant by the luminosity of a star?
Model answer
It is the total radiant power the star emits in all directions, measured in watts.
- 2
What is meant by the radiation intensity received from a star?
Model answer
It is the radiant power arriving per unit area at the detector, measured in W m⁻².
- 3
State the equation relating the intensity received from a star to its luminosity and distance:
Model answer
The equation is I = L/(4πd²), where d is the distance from the source.
- 4
Why does the distance appear as 4πd² in this relationship?
Model answer
The emitted power spreads out uniformly over the surface of a sphere of radius d, and that sphere has area 4πd².
- 5
What happens to the intensity received from a star if its distance from us were three times greater?
Model answer
The intensity would fall to one ninth of its value, because intensity is inversely proportional to the square of the distance.
- 6
A star of luminosity 3.9 × 10²⁶ W is 1.5 × 10¹¹ m away. What intensity is received?
Model answer
I = 3.9 × 10²⁶/(4π × (1.5 × 10¹¹)²) = 1.4 × 10³ W m⁻².
What is inside Levo
Six ways to work the same material.
Space revision questions
- What does Space cover in Edexcel A-Level Physics?
- 7 subtopics: luminosity, intensity and the inverse square law, trigonometric parallax and standard candles, the hertzsprung-russell diagram, the life cycle of stars, the doppler effect and redshift, hubble's law and the age of the universe and dark matter and the fate of the universe. Each one has its own page with questions and model answers.
- How is Space organised?
- By the Edexcel 9PH0 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Space, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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