Astrophysics and Cosmology | OCR A-Level Physics A (H556)
Astrophysics and Cosmology
- 129 questions
- 12 subtopics
- Module 5: Newtonian world and astrophysics
- Paper 1 and Paper 3
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..
It covers 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.
Sample questions from Astrophysics and Cosmology
Answer each one closed book first, then open the answer.
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The solar system and the birth of a star
Why does the collapse of a star-forming cloud accelerate over time?
Show the answer
As the cloud collapses, its density increases, which strengthens gravitational attraction and accelerates the collapse further. -
The death of a low-mass star
Explain how electron degeneracy pressure arises.
Show the answer
Electron degeneracy pressure arises from the Pauli exclusion principle: electrons cannot occupy the same quantum state, creating an outward pressure independent of temperature. -
The Hertzsprung-Russell diagram
In which direction does luminosity increase on an HR diagram?
Show the answer
Luminosity increases upward along the vertical axis. -
Energy levels and emission spectra
Describe the relationship between photon energy and wavelength.
Show the answer
Photon energy is inversely proportional to wavelength; shorter wavelengths correspond to higher energy photons. -
Photon energy and the diffraction grating
How can a transmission diffraction grating be used to determine the wavelength of light?
Show the answer
By measuring the angles at which maxima occur, the wavelength can be calculated using the diffraction grating equation. -
Wien's law and Stefan's law
Calculate the luminosity when stellar radius = 2.1 × 10⁹ m, Stefan constant = 5.67 × 10⁻⁸ W m⁻² K⁻⁴, surface temperature = 12900 K.
Show the answer
Luminosity = 4π × (2.1 × 10⁹)² × 5.67 × 10⁻⁸ × 12900⁴ = 8.70 × 10²⁸ W. -
Doppler shift and Hubble's law
State the Doppler equation for electromagnetic radiation and define each term.
Show the answer
Δf/f = Δλ/λ ≈ v/c, where Δf is the change in frequency, f is the original frequency, Δλ is the change in wavelength, λ is the original wavelength, v is the relative velocity of the source, and c is the speed of light. -
The expanding universe and the Big Bang
Approximately when did recombination occur after the Big Bang?
Show the answer
Approximately 380,000 years after the Big Bang.
The 12 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| The solar system and the birth of a star | Recall 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. | 16 |
| The death of a low-mass star | Recall questions on how a low-mass star becomes a red giant, planetary nebulae, white dwarfs, electron degeneracy pressure and the Chandrasekhar limit. | 9 |
| Supernovae, neutron stars and black holes | Recall 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. | 13 |
| The Hertzsprung-Russell diagram | Recall 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. | 8 |
| Energy levels and emission spectra | Recall questions on discrete energy levels, why they are negative, and how an emission line spectrum arises. | 8 |
| Absorption spectra and spectral lines | Recall 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. | 8 |
| Photon energy and the diffraction grating | Recall 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. | 9 |
| Wien's law and Stefan's law | Recall 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. | 10 |
| Astronomical distances, parallax and the cosmological principle | Recall questions on the astronomical unit, light-year and parsec, stellar parallax and distance calculations, and what homogeneous and isotropic mean in the cosmological principle. | 11 |
| Doppler shift and Hubble's law | Recall questions on the Doppler effect for electromagnetic radiation, recession velocity from redshift, Hubble's law and the Hubble constant, with calculations. | 10 |
| The expanding universe and the Big Bang | Recall 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. | 11 |
| Evidence for the Big Bang and dark energy | Recall 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. | 16 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR A-Level Physics A Active Recall Guide
Every topic, not just this one. 1,862 questions with their answers.