MCQs / Physics / Gravitational Waves

Gravitational Waves MCQs — Physics

60 multiple-choice questions on Gravitational Waves from Physics, each with the correct answer and, where available, a teacher's explanation. Read through them to revise the chapter, then practise the same questions one by one to test yourself.

1. A ring of free particles hit face-on by a gravitational wave would:

  1. move as a whole sideways
  2. stay circular
  3. expand steadily
  4. oscillate between horizontal and vertical ellipses

Answer: D) oscillate between horizontal and vertical ellipses

Explanation: Characteristic GW effect. SLO P-11-D-19 · Knowledge

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2. Which statement is correct?

  1. Gravitational waves heat the Earth's core
  2. Gravitational waves make objects heavier permanently
  3. Gravitational waves are longitudinal sound waves
  4. Gravitational waves stretch and compress objects with mass as they pass

Answer: D) Gravitational waves stretch and compress objects with mass as they pass

Explanation: SLO statement. SLO P-11-D-19 · Knowledge

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3. Interferometers are very sensitive because:

  1. a change in path of a fraction of a wavelength changes the interference
  2. they are very large magnets
  3. lasers are very hot
  4. they use sound waves

Answer: A) a change in path of a fraction of a wavelength changes the interference

Explanation: Light wavelengths are tiny. SLO P-11-D-21 · Understanding

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4. Gravitational waves arriving at two detectors far apart are detected:

  1. at exactly the same time always
  2. only at one detector
  3. at slightly different times, helping locate the source
  4. in reverse order

Answer: C) at slightly different times, helping locate the source

Explanation: Travel at the speed of light between them. SLO P-11-D-20 · Knowledge

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5. A laser interferometer detects gravitational waves by measuring:

  1. radio signals
  2. tiny changes in the lengths of its arms using interference of laser light
  3. changes in temperature
  4. the brightness of stars

Answer: B) tiny changes in the lengths of its arms using interference of laser light

Explanation: Arm lengths change differently. SLO P-11-D-21 · Understanding

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6. The detected gravitational-wave signal typically lasts:

  1. centuries
  2. from a fraction of a second to a few minutes
  3. years
  4. exactly one day

Answer: B) from a fraction of a second to a few minutes

Explanation: The final 'chirp'. SLO P-11-D-20 · Knowledge

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7. Detecting gravitational waves on Earth is very difficult because:

  1. their effect is tiny compared with everyday vibrations
  2. they are invisible
  3. they are blocked by the atmosphere
  4. they travel too fast

Answer: A) their effect is tiny compared with everyday vibrations

Explanation: Noise isolation is essential. SLO P-11-D-20 · Knowledge

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8. Gravitational waves spread outwards from their source:

  1. in all directions
  2. not at all
  3. only towards the Earth
  4. only along a straight beam

Answer: A) in all directions

Explanation: Like ripples from a stone in a pond. SLO P-11-D-18 · Understanding

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9. Gravitational waves travel at:

  1. half the speed of light
  2. the speed of sound
  3. the speed of light
  4. infinite speed

Answer: C) the speed of light

Explanation: Confirmed by observing a neutron-star merger in both GWs and light. SLO P-11-D-18 · Understanding

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10. As two black holes spiral towards each other, the gravitational waves they emit:

  1. increase in frequency and amplitude ('chirp')
  2. decrease in frequency
  3. stop
  4. stay constant

Answer: A) increase in frequency and amplitude ('chirp')

Explanation: Orbit speeds up before merger. SLO P-11-D-18 · Understanding

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11. Gravitational waves are described as waves in:

  1. the intensity of gravity (the curvature of space-time)
  2. air pressure
  3. electric field
  4. water level

Answer: A) the intensity of gravity (the curvature of space-time)

Explanation: As in the SLO description. SLO P-11-D-18 · Understanding

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12. When no gravitational wave passes, LIGO is set so the returning beams interfere:

  1. destructively (dark output)
  2. constructively (bright output)
  3. randomly
  4. not at all

Answer: A) destructively (dark output)

Explanation: A passing wave then lets some light through. SLO P-11-D-21 · Understanding

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13. Gravitational waves are detected using:

  1. laser interferometers such as LIGO
  2. thermometers
  3. Geiger counters
  4. ordinary telescopes

Answer: A) laser interferometers such as LIGO

Explanation: Very sensitive interference of laser beams. SLO P-11-D-21 · Understanding

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14. A gravitational wave of strain 10^-21 would change a 1 m rod's length by:

  1. 10^21 m
  2. 1 m
  3. 10^-3 m
  4. 10^-21 m

Answer: D) 10^-21 m

Explanation: Delta L = hL. SLO P-11-D-20 · Knowledge

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15. Gravitational waves were predicted by:

  1. Isaac Newton
  2. James Clerk Maxwell
  3. Galileo
  4. Albert Einstein

Answer: D) Albert Einstein

Explanation: General relativity (1916). SLO P-11-D-18 · Understanding

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16. The effect of a gravitational wave on a body is described as:

  1. heating
  2. rotation
  3. magnetisation
  4. tidal stretching and squeezing

Answer: D) tidal stretching and squeezing

Explanation: Periodic tidal distortion. SLO P-11-D-19 · Knowledge

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17. The amplitude of a gravitational wave decreases with distance r from its source as:

  1. 1r
  2. r
  3. it doesn't decrease
  4. 1r^2

Answer: A) 1r

Explanation: Amplitude ∝ 1/r (intensity ∝ 1/r^2). SLO P-11-D-20 · Knowledge

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18. Gravitational waves are:

  1. sound waves in space
  2. ripples in space-time produced by accelerating masses
  3. water waves caused by the Moon
  4. electromagnetic waves

Answer: B) ripples in space-time produced by accelerating masses

Explanation: Predicted by Einstein's general relativity. SLO P-11-D-18 · Understanding

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19. The stretching caused by a gravitational wave repeats with:

  1. the mass of the body
  2. the frequency of the wave
  3. no frequency
  4. the speed of light

Answer: B) the frequency of the wave

Explanation: Periodic distortion. SLO P-11-D-19 · Knowledge

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20. Unlike electromagnetic waves, gravitational waves:

  1. travel slower than sound
  2. pass through matter almost unaffected
  3. need a medium
  4. are easily absorbed by dust

Answer: B) pass through matter almost unaffected

Explanation: They interact very weakly. SLO P-11-D-18 · Understanding

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21. We don't notice gravitational waves in daily life because:

  1. the distortions they cause are extremely small
  2. they only affect black holes
  3. they travel too slowly
  4. they never reach the Earth

Answer: A) the distortions they cause are extremely small

Explanation: Minute amplitude. SLO P-11-D-19 · Knowledge

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22. Gravitational waves pass through the Earth:

  1. and are reflected back
  2. and are completely absorbed
  3. only at the poles
  4. almost unaffected

Answer: D) almost unaffected

Explanation: Very weak interaction with matter. SLO P-11-D-20 · Knowledge

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23. LIGO stands for:

  1. Large Inertial Gravity Oscillator
  2. Laser Imaging Galaxy Orbit
  3. Laser Interferometer Gravitational-Wave Observatory
  4. Light Intensity Gravity Observer

Answer: C) Laser Interferometer Gravitational-Wave Observatory

Explanation: US detectors in Hanford and Livingston. SLO P-11-D-21 · Understanding

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24. Which statement is correct?

  1. Gravitational waves are stopped by the ocean
  2. Gravitational waves cannot reach the Earth
  3. Gravitational waves from far-off events pass through the Earth with very small amplitude
  4. Gravitational waves are produced by the Earth's rotation and are large

Answer: C) Gravitational waves from far-off events pass through the Earth with very small amplitude

Explanation: SLO statement. SLO P-11-D-20 · Knowledge

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25. More than one detector is used so that:

  1. detectors are cheaper
  2. more electricity is used
  3. real signals can be confirmed and sources located
  4. the wave is amplified

Answer: C) real signals can be confirmed and sources located

Explanation: Coincidence and triangulation. SLO P-11-D-21 · Understanding

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