Space | Edexcel A-Level Physics (9PH0)
Space
- 72 questions
- 7 subtopics
- Paper 2: Advanced Physics II
- Paper 2 and Paper 3
Paper 2 content on measuring the universe: luminosity and the inverse square law, parallax and standard candles, the Hertzsprung-Russell diagram and stellar life cycles, and the Doppler effect, Hubble's law and what dark matter does to the predicted fate of the universe..
It covers luminosity, intensity and the inverse square law, trigonometric parallax and standard candles, the Hertzsprung-Russell diagram, the life cycle of stars, the Doppler effect and redshift, hubble's law and the age of the universe and dark matter and the fate of the universe.
Sample questions from Space
Answer each one closed book first, then open the answer.
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Luminosity, intensity and the inverse square law
State the equation relating the intensity received from a star to its luminosity and distance:
Show the answer
The equation is I = L/(4πd²), where d is the distance from the source. -
Luminosity, intensity and the inverse square law
A star of luminosity 3.9 × 10²⁶ W is 1.5 × 10¹¹ m away. What intensity is received?
Show the answer
I = 3.9 × 10²⁶/(4π × (1.5 × 10¹¹)²) = 1.4 × 10³ W m⁻². -
Trigonometric parallax and standard candles
A star has a parallax angle of 0.25 arcseconds. How far away is it in parsecs and in metres?
Show the answer
The distance is 1/0.25 = 4.0 pc, which is 4.0 × 3.09 × 10¹⁶ = 1.2 × 10¹⁷ m. -
Trigonometric parallax and standard candles
Why are standard candles needed when parallax already exists?
Show the answer
Parallax angles become unmeasurably small beyond a few thousand parsecs, so standard candles are the only way to reach other galaxies. -
The Hertzsprung-Russell diagram
In what units is luminosity usually shown on a Hertzsprung-Russell diagram?
Show the answer
It is usually given as a multiple of the Sun's luminosity. -
The Hertzsprung-Russell diagram
How can a star be cool and yet extremely luminous?
Show the answer
Its surface area is enormous, and since L = σAT⁴ a very large A can outweigh a low temperature. -
The life cycle of stars
Where would a protostar lie relative to the main sequence, and which way does it move?
Show the answer
It lies to the right of the main sequence, being cool but luminous because of its size, and it moves leftwards as it contracts and heats up. -
The life cycle of stars
What is the eventual fate of a white dwarf?
Show the answer
With no fusion left to sustain it, it simply cools and fades over an immense time, drifting down and to the right on the diagram.
The 7 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Luminosity, intensity and the inverse square law | Recall questions on the difference between luminosity and received intensity, the equation linking them, why 4πd² appears, and the assumptions the equation makes. | 8 |
| Trigonometric parallax and standard candles | Recall questions on the parallax method and its range limit, the astronomical unit and the parsec, what a standard candle is, and why intervening dust distorts a distance. | 14 |
| The Hertzsprung-Russell diagram | Recall questions on what the two axes show and why they are unusual, where the main sequence, red giants and white dwarfs lie, and what fixes a star's position along the main sequence. | 11 |
| The life cycle of stars | Recall questions on the energy source of a main-sequence star, what keeps it stable, how a Sun-like star moves off the sequence, and why the most massive stars are the shortest lived. | 11 |
| The Doppler effect and redshift | Recall questions on the Doppler effect, the definition of redshift and the equations for it, when z ≈ v/c holds, and what a blueshift would mean. | 11 |
| Hubble's law and the age of the universe | Recall questions on the statement of Hubble's law and its constant, why universal recession does not put us at the centre, and estimating the age of the universe from 1/H₀. | 9 |
| Dark matter and the fate of the universe | Recall questions on what dark matter is and the evidence for it, the critical density, how mean density decides the fate, and what distant supernovae revealed. | 8 |
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
Edexcel A-Level Physics Active Recall Guide
Every topic, not just this one. 1,616 questions with their answers.