GCSE Perfect / Physics

GCSE Physics  ›  P.8.3 Red-shift

Red-shift

Free AQA GCSE Physics practice questions on Red-shift. Sample questions below with detailed mark schemes — sign up to practise the full set with spaced repetition.

Start free All Physics topics

Evaluate — 5 marks

Astronomers observe light from a distant galaxy and detect that the wavelength of a specific hydrogen spectral line has shifted from 656 nm (its rest wavelength) to 750 nm. The astronomers use this observation to determine information about the galaxy's motion relative to Earth.

  1. Calculate the wavelength shift for the hydrogen spectral line observed from the distant galaxy. [1 mark]
  2. State what the observation of a red-shift tells us about the motion of the distant galaxy relative to Earth. [1 mark]
  3. Evaluate whether the magnitude of the red-shift observed in this galaxy provides reliable evidence for the expansion of the universe. In your answer, consider what other factors might affect the observed wavelength of light from distant galaxies. [3 marks]
Show mark scheme

Evaluate — 4 marks

Astronomers observe light from a distant galaxy. The hydrogen-alpha spectral line, which has a rest wavelength of 656 nm in the laboratory, is observed at 680 nm in the light from this galaxy. The astronomers use this observation to determine that the galaxy is moving away from Earth.

  1. Calculate the wavelength shift (Δλ) for the hydrogen-alpha spectral line. [1 mark]
  2. The observed red-shift provides evidence that the universe is expanding. Evaluate whether this observation alone is sufficient to conclude that the galaxy is receding from Earth. In your answer, consider what other information or observations would strengthen this conclusion. [3 marks]
Show mark scheme

Suggest — 3 marks

Astronomers observe light from a distant galaxy using a ground-based telescope. The hydrogen alpha spectral line, which normally has a wavelength of 656 nm in the laboratory, is observed at a wavelength of 680 nm. The galaxy is moving away from Earth.

  1. Suggest why the observed wavelength of the hydrogen alpha line is longer than its laboratory wavelength. [1 mark]
  2. Suggest two reasons why the wavelength shift observed from this galaxy might not accurately represent the universe's expansion. [2 marks]
Show mark scheme

Want more questions on Red-shift?

Sign up free for spaced repetition practice tailored to your weak spots.

Create free account
WhatsApp X Reddit
← Previous topic
P.8.2 Orbital motion, natural and artificial satellites

Related topics in Physics