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
Astrophysics
- 14 subtopics
- 60 things to know
- Paper 3, section B
- Paper 3 Section B, one optional topic of five
What Astrophysics covers
Astrophysics is one of the five optional topics, sat on Paper 3. It covers the telescopes used to gather light, the magnitude and spectral schemes used to classify stars, and the red shift evidence for an expanding universe.
Where it is assessed
Paper 3, section B
One optional topic, chosen from five.
Check the AQA specification ↗The 14 subtopics
Each one has its own page.
- Astronomical telescope consisting of two converging lensesThe ray diagram in normal adjustment, and calculating angular magnification from the two focal lengths.Open →
- Reflecting telescopesThe Cassegrain arrangement, spherical and chromatic aberration, and why large telescopes use mirrors.Open →
- Single dish radio telescopes, I-R, U-V and X-ray telescopesComparing telescopes across the spectrum on resolution, collecting power and where they must be sited.Open →
- Advantages of large diameter telescopesCollecting power, the Rayleigh criterion, minimum angular resolution and quantum efficiency.Open →
- Classification by luminosityApparent magnitude as a logarithmic scale, and the intensity ratio between magnitudes.Open →
- Absolute magnitude, MAbsolute magnitude at 10 parsecs, and the distance modulus equation.Open →
- Classification by temperature, black-body radiationStefan's law and Wien's displacement law, and using them to find a star's radius.Open →
- Principles of the use of stellar spectral classesThe classes O through M, their temperatures and colours, and the absorption lines that identify each.Open →
- The Hertzsprung-Russell (HR) diagramThe axes and their unusual scales, the main sequence, and where giants and dwarfs sit.Open →
- Supernovae, neutron stars and black holesType 1a supernovae as standard candles, gamma ray bursts, and the Schwarzschild radius.Open →
- Doppler effectThe frequency and wavelength shift formulae, red and blue shift, and binary star spectra.Open →
- Hubble's lawThe relationship between recession velocity and distance, the Big Bang, and the microwave background.Open →
- QuasarsWhat quasars are, what their large red shifts imply, and calculating their distance and power output.Open →
- Detection of exoplanetsThe radial velocity and transit methods, and reading a light curve.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
Where do rays converge in a telescope in normal adjustment, and how do they arrive?
Process
How do rays leave the eyepiece, where must the intermediate image sit, and what kind of image does the objective form?
Key term
Why does the eyepiece lens have a short focal length?
Process
How does light reach the eyepiece in a Cassegrain telescope?
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What defect does spherical aberration cause, and why is the primary mirror parabolic?
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Why does chromatic aberration affect refractors but not reflectors?
Key term
What problem affects large lenses that are supported only at their edges?
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How does collecting power depend on aperture, and why must radio dishes be so large?
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How are two telescopes' collecting powers compared, which wavebands give the finest resolution, and why must radio dishes be large?
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Why are infrared telescopes sited high up, and what alternatives exist?
Key term
Where are ultraviolet telescopes typically located?
Key term
Why can X-rays not be focused by conventional reflection at normal incidence?
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What does the Rayleigh criterion state, and in what units is angular resolution given?
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What is a radian, and how do wavelength and diameter affect a telescope's performance?
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What is quantum efficiency, and how do a CCD and the human eye compare?
Process
In terms of wavelength sensitivity, how do CCDs differ from the human eye?
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How does a magnitude difference relate to an intensity ratio, and why is brightness subjective?
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Why can apparent magnitude be negative, and what ratio matches five magnitudes?
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What is the distance modulus equation, at what standard distance is absolute magnitude defined, and what three quantities does the equation relate?
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What is needed to find a star's absolute magnitude, and how is distance calculated?
Key term
What is (m − M) called, which two magnitudes give a star's distance, and what is needed to predict its apparent brightness?
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State the conversion factor between parsecs and light years
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What do T and σ mean in Stefan's law, and what does Wien's displacement law state?
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How is a star's luminosity calculated, and how are two stars compared using Stefan's law?
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How is Stefan's law rearranged for radius, and what two conditions on the source does the inverse-square law need?
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What is the value of the constant in Wien's displacement law?
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What colour, temperature and lines characterise class O and B stars?
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What lines and temperature characterise class A stars, and what colour is class F?
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What temperature and lines characterise class F stars, and what colour is class G?
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What lines and temperature characterise class K stars, and what class is a star at 4,200 K?
Key term
What is the intrinsic colour of spectral class M stars?
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From which energy level do electrons start when producing Hydrogen Balmer absorption lines?
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What ranges do the axes of an HR diagram cover, and why is −10 at the top?
Process
Where does the main sequence lie on an HR diagram, and what process powers those stars?
Key term
Why are white dwarfs dim, where do they sit on the diagram, and what class is the Sun?
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What is the approximate absolute magnitude of the Sun?
Key term
What is the name given to the ejected outer layers of a Sun-like star after the red giant phase?
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What is in the Schwarzschild radius formula, and how does a type 1a supernova fade?
Process
What does a gamma ray burst emit, how much energy does it release, and why are type 1a supernovae standard candles?
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What produces a type 1a supernova, and what mass limit must be reached?
Key term
What evidence did observations of type 1a supernovae in distant galaxies provide about the Universe?
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What is the approximate peak absolute magnitude of a type 1a supernova?
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What does Δf mean in the Doppler formula, and what is the redshift parameter z?
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What do Δλ, v and c represent in the redshift formulae?
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When are the Doppler formulae valid, and what sign does z take for a source moving towards us?
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Which radiation do the Doppler formulae apply to, how do a binary star's lines shift as it approaches, and how does the shift vary over an orbit?
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How is a quasar's recession speed found from z, what is it for z = 0.06, and what do quasar spectra reveal?
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What does Hubble's law state, and what does v represent in it?
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What do d and H represent, and what does galactic red shift tell us about the universe?
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What does the Big Bang theory propose, what is the microwave background radiation, and how does it support the theory?
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What is the approximate observed ratio of hydrogen to helium by mass in the universe?
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How is the distance to a quasar estimated, and what do its large red shifts imply?
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What are the first steps in estimating a quasar's distance from its spectrum?
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How is a quasar's power output calculated, and what does F represent?
Key term
What does the term 'quasar' stand for?
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Why is directly imaging an exoplanet hard, and what does the radial velocity method measure?
Process
How does the transit method detect a planet, what sets the depth of the brightness dip, and what orbital alignment does it require?
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What does a transit light curve look like, and how is the orbital period found from it?
Process
What happens to the observed brightness as the planet exits the stellar disc?
Take Astrophysics 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.
Apparent magnitude vs Absolute magnitude
Apparent magnitude: brightness scale as observed from Earth. Absolute magnitude: brightness scale at a standard distance.
Red shift vs Blue shift
Red shift: observed wavelength increased by recession. Blue shift: observed wavelength decreased by approach.
Questions from this topic
Each one with the model answer underneath.
- 1
What two types of lenses make up an astronomical refracting telescope in normal adjustment?
Model answer
Two converging lenses: an objective lens and an eyepiece lens.
- 2
How are the objective and eyepiece lenses positioned relative to each other in a telescope in normal adjustment?
Model answer
They are arranged so that the focal point of the objective lens coincides with the focal point of the eyepiece lens.
- 3
Where is the final image formed when an astronomical telescope is in normal adjustment?
Model answer
At infinity.
- 4
Why is viewing through a telescope in normal adjustment comfortable for the eye?
Model answer
Because the final image is at infinity, so the eye is relaxed when viewing.
- 5
Describe the nature of the image formed by the objective lens of an astronomical telescope.
Model answer
A real, inverted, diminished image.
- 6
Where does the objective lens form its image of a distant object?
Model answer
At its focal point.
What is inside Levo
Six ways to work the same material.
Astrophysics revision questions
- What does Astrophysics cover in AQA A-Level Physics?
- 14 subtopics: astronomical telescope consisting of two converging lenses, reflecting telescopes, single dish radio telescopes, i-r, u-v and x-ray telescopes, advantages of large diameter telescopes, classification by luminosity, absolute magnitude, m, classification by temperature, black-body radiation, principles of the use of stellar spectral classes, the hertzsprung-russell (hr) diagram, supernovae, neutron stars and black holes, doppler effect, hubble's law, quasars and detection of exoplanets. Each one has its own page with questions and model answers.
- How is Astrophysics organised?
- By the AQA 7408 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Astrophysics, 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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