Lesson 3.9

3.9 Astrophysics: telescopes, classification of stars, cosmology Quiz: AQA Physics, Unit 9

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.9, Astrophysics: telescopes, classification of stars, cosmology: 20 multiple choice questions for the AQA Physics (7408), Unit 9: Astrophysics (A-level option), written with Revision Ninja.

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The 20 questions

  1. Which expression gives the minimum angular resolution of a telescope of aperture D observing light of wavelength lambda?

    • theta approximately lambda squared / D
    • theta approximately lambda x D
    • theta approximately D / lambda
    • theta approximately lambda / D

  2. How does the light-collecting power of a telescope depend on its objective diameter?

    • It is proportional to the cube of the diameter
    • It is inversely proportional to the diameter
    • It is proportional to the square of the diameter
    • It is proportional to the diameter

  3. What is the angular magnification of an astronomical telescope in normal adjustment?

    • M = fo x fe, the product of the two focal lengths
    • M = fo + fe, the sum of the two focal lengths
    • M = fo / fe, the objective focal length divided by the eyepiece focal length
    • M = fe / fo, the eyepiece focal length divided by the objective focal length

  4. What is the arrangement of a Cassegrain reflecting telescope?

    • a parabolic concave primary mirror and a convex secondary mirror
    • two concave lenses placed on the same axis
    • a flat primary mirror and a convex lens eyepiece
    • a parabolic convex primary mirror and a concave secondary mirror

  5. Which aberration is a key disadvantage of refracting telescopes that reflecting telescopes largely avoid?

    • diffraction caused by the support struts of the mirror
    • chromatic aberration, caused by different wavelengths focusing at different points
    • coma caused by the secondary mirror
    • seeing caused only by the atmosphere above the telescope

  6. A star's apparent magnitudes differ by 1. What is the ratio of their brightnesses?

    • about 10
    • about 1.58
    • about 100
    • about 2.51

  7. Which equation relates apparent magnitude m, absolute magnitude M and distance d in parsecs?

    • m + M = 5 log10(d)
    • m - M = 5 log10(d / 10)
    • m - M = log10(d) / 5
    • m - M = 5 log10(10 / d)

  8. A star has apparent magnitude 6 at a distance of 100 parsecs. What is its absolute magnitude?

    • 6
    • -1
    • 11
    • 1

  9. A star has a peak wavelength of 500 nm in its black-body spectrum. Using Wien's displacement law with constant 2.9 x 10^-3 m K, what is its surface temperature?

    • 5800 K
    • 5.8 x 10^6 K
    • 580 K
    • 2900 K

  10. Two stars have the same surface temperature, but one has twice the radius of the other. What is the ratio of their power outputs?

    • 4 : 1
    • 1 : 1
    • 2 : 1
    • 8 : 1

  11. A galaxy has a recession speed of 7000 km/s. Using Hubble's constant H0 = 70 km/s per Mpc, what is its distance?

    • 490 Mpc
    • 100 Mpc
    • 7000 Mpc
    • 10 Mpc

  12. A galaxy has redshift z = 0.01 for a recession speed much less than c. What is its recession speed?

    • 30 km/s
    • 30 000 km/s
    • 3000 km/s
    • 300 km/s

  13. What is the approximate Schwarzschild radius of a black hole with the mass of the Sun?

    • about 3 m
    • about 30 km
    • about 3 km
    • about 300 m

  14. What defines a black hole?

    • its density is the same as water
    • its temperature is higher than that of a neutron star
    • it emits strong gamma rays from its surface
    • the escape velocity at its surface exceeds the speed of light

  15. Why are Type 1a supernovae used as standard candles?

    • they are always the brightest objects in the sky
    • they pulse at a fixed frequency that gives their distance
    • they have a consistent peak absolute magnitude, so their apparent brightness gives their distance
    • they emit identical spectra, so their distance follows from their colour

  16. Using Hubble's constant H0 = 70 km/s per Mpc, what is the approximate age of the Universe if H0 is assumed constant?

    • about 140 billion years
    • about 4.6 billion years
    • about 1.4 billion years
    • about 14 billion years

  17. A spectral line at 500 nm shifts by 0.02 nm due to the Doppler effect. What is the speed of the source?

    • 1.2 km/s
    • 0.12 km/s
    • 12 km/s
    • 120 km/s

  18. What is the minimum angular resolution of a 2.5 m diameter telescope observing light of wavelength 500 nm?

    • 5.0 x 10^-7 rad
    • 8.0 x 10^-8 rad
    • 2.0 x 10^-7 rad
    • 2.0 x 10^-5 rad

  19. Why is a CCD often preferred to the eye as a detector in astronomy?

    • it has a higher quantum efficiency and can integrate light over long exposures
    • it cannot detect faint objects but is more convenient to use
    • it detects only infrared light
    • it has a lower quantum efficiency but a sharper image

  20. A star dims by 1% during a transit by a planet. What can be deduced about the planet?

    • its radius is about one tenth of the star's radius
    • its mass is one percent of the star's mass
    • its radius is one hundredth of the star's radius
    • its radius equals the star's radius

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