Process
OCR A-Level Physics A H556
Practical Skills in the Written Papers
The Practical Endorsement
Topic overviewAnalogue and digital measuring instrumentsImproving accuracy with repeat timing, fiducial markers and plumb linesTiming, calipers and micrometersConstructing and testing circuitsSignal generators and oscilloscopesGenerating and measuring wavesData loggers, modelling software and ionising radiation
Physical Quantities and Units
Making Measurements and Analysing Data
Nature of Quantities
Motion
Forces in Action
Work, Energy and Power
Materials
Newton’s Laws of Motion and Momentum
Charge and Current
Energy, Power and Resistance
Electrical Circuits
Waves
Topic overviewProgressive waves and their propertiesThe wave equationReflection, refraction and diffractionWave graphs and intensityThe electromagnetic spectrumPolarisationRefraction and refractive indexCritical angle and total internal reflectionThe principle of superpositionInterference, coherence and path differenceTwo-source interference, Young's double-slit experiment and the diffraction gratingForming stationary wavesStationary waves on strings and in air columnsMeasuring the speed of soundNode spacing, amplitude and phase in stationary wavesHarmonics and the fundamental mode
Quantum Physics
Thermal Physics
Topic overviewThermal equilibrium and absolute temperatureThe kinetic model of solids, liquids and gasesBrownian motion and internal energySpecific heat capacityMeasuring specific heat capacitySpecific latent heatMeasuring specific latent heatMoles, the Avogadro constant and kinetic theoryGas laws, the ideal gas equation and r.m.s. speedMaxwell-Boltzmann distribution, Boltzmann constant and internal energy
Oscillations
Gravitational Fields
Astrophysics and Cosmology
Topic overviewThe solar system and the birth of a starThe death of a low-mass starSupernovae, neutron stars and black holesThe Hertzsprung-Russell diagramEnergy levels and emission spectraAbsorption spectra and spectral linesPhoton energy and the diffraction gratingWien's law and Stefan's lawAstronomical distances, parallax and the cosmological principleDoppler shift and Hubble's lawThe expanding universe and the Big BangEvidence for the Big Bang and dark energy
Capacitors
Topic overviewCapacitance and charging a capacitorCapacitors in seriesCapacitors in parallel and combined circuitsEnergy stored by a capacitorCharging and discharging through a resistorInvestigating capacitor dischargeThe time constantIterative modelling, exponential decay and the constant-ratio property
Electric Fields
Electromagnetism
Nuclear and Particle Physics
Topic overviewAlpha-particle scattering and the nuclear modelProton number, nucleon number and isotopesThe strong nuclear force and nuclear radiusParticles, antiparticles and hadronsLeptons and the quark modelQuark composition and chargesBeta decay in the quark modelRadioactive decay and the three radiationsNuclear decay equationsActivity, decay constant and half-lifeExponential decay and radioactive datingMass-energy equivalenceAnnihilation, mass defect and binding energyBinding energy per nucleon and induced fissionThe fission reactor and nuclear wasteNuclear fusion and balancing nuclear equations
Astrophysics and Cosmology
- 12 subtopics
- 36 things to know
- Papers 1, 2 and 3
What Astrophysics and Cosmology covers
How stars form, live and die, what their light reveals about them, and the evidence that the universe is expanding from a hot dense beginning.
Where it is assessed
Papers 1, 2 and 3
Newtonian world, astrophysics and particles, drawn on across the papers.
Check the OCR specification ↗The 12 subtopics
Each one has its own page.
- The solar system and the birth of a starRecall questions on solar systems, planets, planetary satellites, comets, galaxies and the universe, and how a star forms from an interstellar cloud through gravitational collapse, fusion and the balance of radiation and gas pressure.Open →
- The death of a low-mass starRecall questions on how a low-mass star becomes a red giant, planetary nebulae, white dwarfs, electron degeneracy pressure and the Chandrasekhar limit.Open →
- Supernovae, neutron stars and black holesRecall questions on red supergiants and fusion in massive stars, the iron core and supernovae, and the formation and properties of neutron stars and black holes.Open →
- The Hertzsprung-Russell diagramRecall questions on the axes of the Hertzsprung-Russell diagram, the positions of main sequence stars, red giants, red supergiants and white dwarfs, and how a low-mass star moves across the diagram as it evolves.Open →
- Energy levels and emission spectraRecall questions on discrete energy levels, why they are negative, and how an emission line spectrum arises.Open →
- Absorption spectra and spectral linesRecall questions on how emission lines are produced, continuous, emission and absorption line spectra, why each element has its own line pattern, and identifying the elements in a star.Open →
- Photon energy and the diffraction gratingRecall questions on photon energy in terms of wavelength and frequency, and using a transmission diffraction grating: grating spacing, d sin θ = nλ and calculating wavelength.Open →
- Wien's law and Stefan's lawRecall questions on Wien's displacement law, luminosity, Stefan's law and its calculations, and using Wien's law and Stefan's law together to estimate the radius of a star.Open →
- Astronomical distances, parallax and the cosmological principleRecall questions on the astronomical unit, light-year and parsec, stellar parallax and distance calculations, and what homogeneous and isotropic mean in the cosmological principle.Open →
- Doppler shift and Hubble's lawRecall questions on the Doppler effect for electromagnetic radiation, recession velocity from redshift, Hubble's law and the Hubble constant, with calculations.Open →
- The expanding universe and the Big BangRecall questions on redshift as evidence of expansion, units of the Hubble constant, the Big Bang theory, and the stages of the early universe including nucleosynthesis, recombination and the release of the CMB.Open →
- Evidence for the Big Bang and dark energyRecall questions on the cosmic microwave background as evidence for the Big Bang, estimating the age of the universe from the Hubble constant, dark energy, dark matter and ordinary matter.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
What happens in a low-mass star when its core hydrogen is exhausted, why does it expand into a red giant, and what fusion can then occur in its core?
Key term
Define a white dwarf, and explain how the electron degeneracy pressure that supports it arises.
Numbers
State the equation that relates the energy of an emitted photon to the energy levels involved in an electron transition, and explain why blue light photons carry more energy than red light photons.
Numbers
State the equation that relates the energy of a photon to its wavelength, and describe the relationship between photon energy and wavelength.
Key term
To estimate a star's radius, how are Wien's law and then Stefan's law used, and what does σ in Stefan's law represent?
Numbers
Define the astronomical unit and the light-year, and state the equation relating parallax angle to distance.
Key term
What stellar remnant forms after a supernova if the core mass is below about three solar masses?
Process
Why does a massive star become a red supergiant after leaving the main sequence?
Key term
In which direction does luminosity increase on an HR diagram?
Process
In the process of emission line production, what is the initial state of the electron?
Key term
How can a transmission diffraction grating be used to determine the wavelength of light?
Numbers
State Stefan's law and explain how luminosity depends on temperature.
Key term
When was the CMB radiation we observe today released?
Key term
In what two types of units can the Hubble constant be expressed?
Key term
What does the Big Bang theory propose about the origin of the universe?
Key term
What expanded as a result of the Big Bang?
Key term
State the equation used to estimate the age of the universe from the Hubble constant.
Key term
What constitutes a solar system?
Key term
Why does fusion cease when an iron core forms in a massive star?
Key term
Why can electrons in isolated gas atoms only exist at certain energies rather than any energy they choose?
Key term
What happens to an electron during the production of an emission spectral line?
Key term
What is a light-year?
Key term
What happens to the observed frequency of electromagnetic radiation when the source moves towards the observer?
Key term
Define a galaxy.
Key term
What is a planetary satellite?
Key term
What happens when fusion stops in the iron core of a massive star?
Key term
What energy transformation occurs as a protostellar cloud collapses, and what effect does this have?
Key term
What energy value is assigned to the ionisation level of an atom, and what does this represent physically?
Key term
Why do different elements produce different spectral line patterns?
Key term
Explain why blue light photons carry more energy than red light photons.
Numbers
What equation would you use to calculate photon energy if you know the frequency of the radiation?
Key term
State the equation relating parallax angle to distance, defining each term.
Key term
What happens to the observed wavelength of electromagnetic radiation when the source moves away from the observer?
Numbers
Calculate the recession velocity when change in wavelength = 19 nm, rest wavelength = 460 nm, speed of light = 3.00 × 10⁸ m s⁻¹.
Key term
What is the cosmic microwave background (CMB) radiation and at what temperature is it observed?
Take Astrophysics and Cosmology further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Luminosity vs Intensity
Luminosity: total power emitted by a star. Intensity: power received per unit area.
Red shift vs Blue shift
Red shift: observed wavelength increased by recession. Blue shift: observed wavelength decreased by approach.
White dwarf vs Neutron star
White dwarf: compact remnant supported by electron degeneracy pressure. Neutron star: compact remnant supported mainly by neutron degeneracy pressure.
Questions from this topic
Each one with the model answer underneath.
- 1
What constitutes a solar system?
Model answer
A solar system consists of a star together with all the planets, moons, asteroids, comets and other objects gravitationally bound to it.
- 2
Define a galaxy.
Model answer
A galaxy is a large system of stars, gas, dust and dark matter held together by gravity, typically containing billions of stars.
- 3
What is meant by the universe?
Model answer
The universe is the totality of all space, time, matter and energy, encompassing all galaxies and the space between them.
- 4
What materials are present in the interstellar cloud from which stars form?
Model answer
The interstellar cloud contains hydrogen and helium gas plus dust.
- 5
What causes an interstellar cloud to begin collapsing during star formation?
Model answer
Gravitational attraction between particles in the cloud causes it to collapse.
- 6
Why does the collapse of a star-forming cloud accelerate over time?
Model answer
As the cloud collapses, its density increases, which strengthens gravitational attraction and accelerates the collapse further.
What is inside Levo
Six ways to work the same material.
Astrophysics and Cosmology revision questions
- What does Astrophysics and Cosmology cover in OCR A-Level Physics A?
- 12 subtopics: the solar system and the birth of a star, the death of a low-mass star, supernovae, neutron stars and black holes, the hertzsprung-russell diagram, energy levels and emission spectra, absorption spectra and spectral lines, photon energy and the diffraction grating, wien's law and stefan's law, astronomical distances, parallax and the cosmological principle, doppler shift and hubble's law, the expanding universe and the big bang and evidence for the big bang and dark energy. Each one has its own page with questions and model answers.
- How is Astrophysics and Cosmology organised?
- By the OCR H556 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Astrophysics and Cosmology, 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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