Astrophysics | AQA A-Level Physics (7408)
Astrophysics
- 333 questions
- 14 subtopics
- Paper 3 Section B: one option of five
- Paper 3
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.
Sample questions from Astrophysics
Answer each one closed book first, then open the answer.
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Astronomical telescope consisting of two converging lenses
Where must the intermediate image be positioned relative to the eyepiece for the telescope to be in normal adjustment?
Show the answer
At the focal point of the eyepiece lens. -
Reflecting telescopes
State one optical advantage that reflecting telescopes have over refracting telescopes.
Show the answer
Reflecting telescopes are free from chromatic aberration. -
Advantages of large diameter telescopes
Why does using shorter wavelengths of light improve a telescope's angular resolution?
Show the answer
Shorter wavelengths decrease the minimum resolvable angle θ, allowing finer details to be distinguished. -
Classification by luminosity
Why is brightness described as a subjective scale of measurement?
Show the answer
Because brightness is based on human perception of light intensity rather than an objective physical measurement. -
Classification by temperature, black-body radiation
What determines the position of the peak on a black-body radiation curve?
Show the answer
The peak occurs at a characteristic wavelength that depends on the temperature of the black body. -
Principles of the use of stellar spectral classes
What is the intrinsic colour of spectral class M stars?
Show the answer
Red -
Supernovae, neutron stars and black holes
How does the energy released in a gamma ray burst compare to the Sun's total lifetime energy output?
Show the answer
The energy released can exceed the total energy output of the Sun over its entire lifetime, released in just seconds to minutes. -
Doppler effect
Calculate the orbital velocity when speed of light = 3.00 × 10⁸ m s⁻¹, wavelength shift = 0.06 nm, rest wavelength = 472 nm.
Show the answer
Orbital velocity = 3.00 × 10⁸ × 0.06 ÷ 472 = 38100 m s⁻¹.
The 14 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Astronomical telescope consisting of two converging lenses | The ray diagram in normal adjustment, and calculating angular magnification from the two focal lengths. | 23 |
| Reflecting telescopes | The Cassegrain arrangement, spherical and chromatic aberration, and why large telescopes use mirrors. | 24 |
| Single dish radio telescopes, I-R, U-V and X-ray telescopes | Comparing telescopes across the spectrum on resolution, collecting power and where they must be sited. | 32 |
| Advantages of large diameter telescopes | Collecting power, the Rayleigh criterion, minimum angular resolution and quantum efficiency. | 22 |
| Classification by luminosity | Apparent magnitude as a logarithmic scale, and the intensity ratio between magnitudes. | 10 |
| Absolute magnitude, M | Absolute magnitude at 10 parsecs, and the distance modulus equation. | 23 |
| Classification by temperature, black-body radiation | Stefan's law and Wien's displacement law, and using them to find a star's radius. | 23 |
| Principles of the use of stellar spectral classes | The classes O through M, their temperatures and colours, and the absorption lines that identify each. | 33 |
| The Hertzsprung-Russell (HR) diagram | The axes and their unusual scales, the main sequence, and where giants and dwarfs sit. | 27 |
| Supernovae, neutron stars and black holes | Type 1a supernovae as standard candles, gamma ray bursts, and the Schwarzschild radius. | 25 |
| Doppler effect | The frequency and wavelength shift formulae, red and blue shift, and binary star spectra. | 26 |
| Hubble's law | The relationship between recession velocity and distance, the Big Bang, and the microwave background. | 22 |
| Quasars | What quasars are, what their large red shifts imply, and calculating their distance and power output. | 25 |
| Detection of exoplanets | The radial velocity and transit methods, and reading a light curve. | 18 |
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
AQA A-Level Physics Active Recall Guide
Every topic, not just this one. 3,682 questions with their answers.