Process
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
Astrophysics
Reflecting telescopes
- 4 things to know
- Paper 3, section B
Overview
The Cassegrain arrangement, spherical and chromatic aberration, and why large telescopes use mirrors.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
What defect does spherical aberration cause, and why is the primary mirror parabolic?
Numbers
Why does chromatic aberration affect refractors but not reflectors?
Key term
What problem affects large lenses that are supported only at their edges?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What type of surface does the primary mirror in a Cassegrain telescope have, and what effect does this have on incoming parallel rays?
Model answer
It has a concave surface, which converges parallel rays towards a focal point.
- 2
Why is the primary mirror in a reflecting telescope made as large as practically possible?
Model answer
A large primary mirror maximises light-gathering power, allowing fainter objects to be observed.
- 3
Describe the state of light rays entering a Cassegrain telescope from a distant astronomical object.
Model answer
The rays are parallel because the object is effectively at infinity.
- 4
What shape is the secondary mirror in a Cassegrain reflecting telescope, and what effect does this shape have on light rays?
Model answer
The secondary mirror is convex, which diverges the rays striking it.
- 5
Where is the secondary mirror positioned relative to the focal point of the primary mirror in a Cassegrain telescope?
Model answer
It is positioned before (in front of) the focal point of the primary mirror, intercepting the converging rays.
- 6
How does light reach the eyepiece in a Cassegrain telescope after striking the secondary mirror?
Model answer
The convex secondary mirror reflects light back through a hole in the centre of the primary mirror to the eyepiece.
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