Lesson 10.3.1

10.3.1 Doppler effect and redshift Quiz: Pearson Edexcel Physics, Unit 10

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson 10.3.1, Doppler effect and redshift: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 10: Space, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. What happens to observed wavelength when a wave source moves away from an observer?

    • It remains constant
    • It increases
    • It becomes zero
    • It decreases

  2. For a source receding at a speed much less than c, which expression gives the redshift z?

    • z = c v
    • z = v^2 / c
    • z = v / c
    • z = c / v

  3. What does the cosmological redshift of distant galaxies provide evidence for?

    • Rotating universe
    • Expanding universe
    • Shrinking universe
    • Static universe

  4. According to Hubble's law, what is galaxy recession speed directly proportional to?

    • Distance from Earth
    • Galaxy radius
    • Galactic mass
    • Absolute luminosity

  5. What happens to the observed frequency of light when a source moves towards an observer?

    • It increases
    • It decreases
    • It drops to zero
    • It stays constant

  6. A spectral line with rest wavelength 656 nm is observed at 660 nm. What is the approximate recession speed? Use c = 3.0 x 10^8 m s^-1.

    • 4.0 x 10^5 m s^-1
    • 6.6 x 10^6 m s^-1
    • 1.8 x 10^6 m s^-1
    • 1.8 x 10^8 m s^-1

  7. A galaxy has Hubble constant H0 = 70 km s^-1 Mpc^-1. What is its recession speed at 100 Mpc?

    • 70 km s^-1
    • 14000 km s^-1
    • 7000 km s^-1
    • 700 km s^-1

  8. A galaxy recedes at 2100 km s^-1 with H0 = 70 km s^-1 Mpc^-1. What is its distance?

    • 3 Mpc
    • 300 Mpc
    • 30 Mpc
    • 0.03 Mpc

  9. A line of frequency 5.0 x 10^14 Hz is observed at 4.9 x 10^14 Hz. What is the approximate recession speed? Use c = 3.0 x 10^8 m s^-1.

    • 1.5 x 10^8 m s^-1
    • 6.0 x 10^6 m s^-1
    • 2.0 x 10^7 m s^-1
    • 6.0 x 10^5 m s^-1

  10. A galaxy has redshift z = 0.2. What is its approximate recession speed? Use c = 3.0 x 10^8 m s^-1.

    • 6.0 x 10^8 m s^-1
    • 1.5 x 10^7 m s^-1
    • 3.0 x 10^8 m s^-1
    • 6.0 x 10^7 m s^-1

  11. Why is the non-relativistic Doppler formula v = z c limited to speeds v << c?

    • Light speed varies
    • Redshift becomes zero
    • Relativistic effects apply
    • Hubble constant changes

  12. A galaxy's spectral line is shifted by 1.0% from its rest wavelength. With H0 = 70 km s^-1 Mpc^-1, roughly how far away is it?

    • about 430 Mpc
    • about 0.43 Mpc
    • about 43 Mpc
    • about 4.3 Mpc

  13. Galaxy B is twice as far as Galaxy A. What is Galaxy B's recession speed?

    • Twice A's speed
    • Four times A's speed
    • Same as A's speed
    • Half A's speed

  14. A spectral line emitted at 486 nm is observed at 500 nm. What is the redshift z?

    • 0.029
    • 2.9
    • 0.34
    • 0.0097

  15. Why does light from a receding star shift to longer wavelengths?

    • Photons lose mass
    • Light speed decreases
    • Wavelengths are stretched
    • Wavelengths are compressed

  16. For a receding source, how does observed frequency compare to emitted frequency?

    • It is identical
    • It is zero
    • It is lower
    • It is higher

  17. A galaxy's light shows a Doppler shift of z = 0.05. What is its approximate recession speed?

    • 5.0 x 10^5 m s^-1
    • 1.5 x 10^7 m s^-1
    • 1.5 x 10^6 m s^-1
    • 6.0 x 10^7 m s^-1

  18. A galaxy's spectral line with rest wavelength 500 nm is observed at 520 nm. What is its redshift?

    • 0.04
    • 0.02
    • 4.0
    • 0.96

  19. A star approaches Earth at 3.0 x 10^6 m s^-1. What is the approximate fractional change in observed frequency, Δ f / f?

    • 0.10
    • 0.0010
    • 1.0
    • 0.010

  20. What spectral observation indicates that a galaxy is moving towards Earth?

    • Redshifted spectral lines
    • Unshifted spectral lines
    • Blueshifted spectral lines
    • Broadened spectral lines

All Pearson Edexcel Physics quizzes