AQA GCSE Physics (8463), Higher tier · Space physics
Practise Red-shift. 14 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Astronomers study the light from distant galaxies. What is meant by red-shift?
An increase in the observed wavelength of the light from a galaxy.
Describe what the Big Bang theory suggests about the beginning of the universe.
The universe began from a very small region that was extremely hot and dense.
State whether the wavelength of light from a red-shifted galaxy is longer or shorter than it would be from a stationary source.
Longer.
Scientists think that there is still much about the universe that is not understood. Give one example of something about the universe that is not yet understood.
Dark mass (dark matter) or dark energy.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Astronomers study the light from distant galaxies.
(a) What is meant by red-shift?[1]
(b) What does the red-shift of the light from a galaxy show about the motion of the galaxy?[1]
(c) How does the red-shift of very distant galaxies compare with the red-shift of nearer galaxies? Tick (✓) one box.[1]
Very distant galaxies show a bigger red-shift.
Very distant galaxies show a smaller red-shift.
All galaxies show the same red-shift.
(d) Name the theory about the origin of the universe that is supported by red-shift.[1]
Show the answer and mark scheme
(a)Answer: An increase in the observed wavelength of the light from a galaxy.
an observed increase in the wavelength of light from (distant) galaxies
(b)Answer: It is moving away from us.
the galaxy is moving away from us / from the Earth
(c)Answer: Very distant galaxies show a bigger red-shift.
(d)Answer: The Big Bang theory
the Big Bang theory
Question 2Medium6 marks
Most scientists accept the Big Bang theory of the origin of the universe.
(a) Describe what the Big Bang theory suggests about the beginning of the universe.[2]
(b) Observations show that the further away a galaxy is, the faster it is moving away from us. Explain how this supports the idea that the universe is expanding.[2]
(c) Nobody observed the beginning of the universe. Suggest why scientists accept the Big Bang theory.[2]
Show the answer and mark scheme
(a)Answer: The universe began from a very small region that was extremely hot and dense.
the universe began from a very small region
that was extremely hot and dense
(b)Answer: Galaxies in every direction are receding, faster the further they are, which is what happens if space itself is expanding.
(almost) all distant galaxies are moving away from us
the more distant galaxies moving faster is what is expected if space itself is expanding (everything is moving apart from everything else)
(c)Answer: It explains the evidence, such as red-shift, which has been confirmed by many independent observations.
the theory explains the observations (e.g. the red-shift of distant galaxies)
the observations have been checked / repeated by many scientists, and predictions made by the theory have been confirmed
Question 3Hard6 marks
Explain how observations of the light from distant galaxies provide evidence for the Big Bang theory. Your answer should include what is still not understood about the universe.[6]
Show the answer and mark scheme
Answer: Level-of-response answer: red-shift → galaxies receding, faster when further away → space is expanding → the universe was once very small, hot and dense (Big Bang); dark mass and dark energy are not yet understood.
light from most distant galaxies is red-shifted: the observed wavelengths are increased
red-shift shows that the galaxies are moving away from us
the further away a galaxy is, the greater its red-shift, so the faster it is moving away
this shows that space itself (the universe) is expanding
if the universe is expanding, it must have been smaller in the past
tracing the expansion back suggests the universe began from a very small region that was extremely hot and dense: the Big Bang
since 1998, observations of supernovae suggest that distant galaxies are moving away ever faster (the expansion is accelerating)
there is still much that is not understood, e.g. dark mass (dark matter) and dark energy
Marked with levels of response: the full level descriptors are in the app.
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