Numbers
AQA A-Level Physics 7408
Measurements and Their Errors
Particles and Radiation
Topic overviewConstituents of the atomStable and unstable nucleiParticles, antiparticles and photonsParticle interactionsClassification of particlesQuarks and antiquarksApplications of conservation lawsThe photoelectric effectCollisions of electrons with atomsEnergy levels and photon emissionWave-particle duality
Waves
Mechanics and Materials
Electricity
Further Mechanics and Thermal Physics
Fields and Their Consequences
Topic overviewFieldsNewton's lawGravitational field strengthGravitational potentialOrbits of planets and satellitesCoulomb's lawElectric field strengthElectric potentialCapacitanceParallel plate capacitorEnergy stored by a capacitorCapacitor charge and dischargeMagnetic flux densityMoving charges in a magnetic fieldMagnetic flux and flux linkageElectromagnetic inductionAlternating currentsTransformers
Nuclear Physics
AstrophysicsOptional topic
Topic overviewAstronomical telescope consisting of two converging lensesReflecting telescopesSingle dish radio telescopes, I-R, U-V and X-ray telescopesAdvantages of large diameter telescopesClassification by luminosityAbsolute magnitude, MClassification by temperature, black-body radiationPrinciples of the use of stellar spectral classesThe Hertzsprung-Russell (HR) diagramSupernovae, neutron stars and black holesDoppler effectHubble's lawQuasarsDetection of exoplanets
Medical PhysicsOptional topic
Topic overviewPhysics of visionDefects of vision and their correction using lensesEar as a sound detection systemSensitivity and frequency responseDefects of hearingSimple ECG machines and the normal ECG waveformUltrasound imagingFibre optics and endoscopyMagnetic resonance (MR) scannerThe physics of diagnostic X-raysImage detection and enhancementAbsorption of X-raysCT scannerImaging techniquesHalf-lifeGamma cameraUse of high-energy X-raysUse of radioactive implantsImaging comparisons
Engineering PhysicsOptional topic
Turning Points in PhysicsOptional topic
Topic overviewCathode raysThermionic emission of electronsSpecific charge of the electronPrinciple of Millikan's determination of the electronic charge, eNewton's corpuscular theory of lightSignificance of Young's double slits experimentElectromagnetic wavesThe discovery of photoelectricityWave–particle dualityElectron microscopesThe Michelson-Morley experimentEinstein's theory of special relativityTime dilationLength contractionRelativistic mass and energy
ElectronicsOptional topic
Topic overviewMOSFET (metal-oxide semiconducting field-effect transistor)Zener diodePhotodiodeHall effect sensorDifference between analogue and digital signalsLC resonance filtersThe ideal operational amplifierInverting amplifier configurationNon-inverting amplifier configurationSumming amplifier configurationReal operational amplifiersCombinational logicSequential logicAstablesPrinciples of communication systemsTransmission mediaTime-division multiplexingAmplitude (AM) and frequency modulation (FM) techniques
Turning Points in Physics
Time dilation
- 3 things to know
- Paper 3, section B
Overview
The Lorentz factor, proper time, and the muon evidence.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
Why does γ grow as v approaches c, what happens to time dilation then, and why is it negligible at everyday speeds?
Numbers
What is the proper lifetime of a muon?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is proper time?
Model answer
Proper time is the time interval between two events measured by an observer for whom both events occur at the same position in space.
- 2
In the time dilation equation, what does t₀ represent and who measures it?
Model answer
t₀ represents the proper time, measured by an observer for whom the two events occur at the same position in space.
- 3
Define time dilation.
Model answer
Time dilation is the phenomenon where a moving clock runs slower relative to a stationary observer compared to a clock at rest in the observer's frame.
- 4
What fundamental principles give rise to time dilation?
Model answer
Time dilation is a direct consequence of the postulates of special relativity.
- 5
State the time dilation formula and identify each quantity.
Model answer
t = t₀/√(1 − v²/c²), where t is the dilated time, t₀ is the proper time, v is the relative velocity, and c is the speed of light.
- 6
When would you use the time dilation formula t = t₀/√(1 − v²/c²)?
Model answer
When calculating the dilated time observed in one reference frame from the proper time measured in a frame moving at relative velocity v.
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