MCQs / Physics / Gravitational Waves

Gravitational Waves MCQs — Physics (page 2)

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.

26. Gravitational waves reach the Earth:

  1. only once a century
  2. never
  3. only during eclipses
  4. constantly but mostly too weak to detect

Answer: D) constantly but mostly too weak to detect

Explanation: Detectors pick out the strongest. SLO P-11-D-20 · Knowledge

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27. The first detected gravitational waves came from:

  1. a supernova in our galaxy
  2. the merger of two black holes
  3. the Big Bang directly
  4. the Sun

Answer: B) the merger of two black holes

Explanation: Event GW150914. SLO P-11-D-18 · Understanding

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28. A planned space-based gravitational-wave interferometer is:

  1. GPS
  2. LIGO-Mars
  3. Hubble
  4. LISA

Answer: D) LISA

Explanation: Laser Interferometer Space Antenna. SLO P-11-D-21 · Understanding

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29. By the time they reach the Earth, gravitational waves have:

  1. very large amplitude
  2. become light waves
  3. very minute amplitude
  4. zero speed

Answer: C) very minute amplitude

Explanation: They weaken with distance. SLO P-11-D-20 · Knowledge

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30. Gravitational waves are transverse because the stretching and squeezing occur:

  1. in no direction
  2. perpendicular to the direction of travel
  3. along the direction of travel
  4. only at the source

Answer: B) perpendicular to the direction of travel

Explanation: Like EM waves. SLO P-11-D-19 · Knowledge

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31. If a gravitational wave stretches a 4 km detector arm by 10^-18 m, the strain is about:

  1. 10^-18
  2. 2.5 10^-22
  3. 4 10^3
  4. 4 10^-15

Answer: B) 2.5 10^-22

Explanation: Strain = Delta LL = 10^-184000. SLO P-11-D-19 · Knowledge

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32. The 2017 Nobel Prize in Physics was awarded for:

  1. the Higgs boson
  2. discovery of the electron
  3. invention of the laser
  4. the detection of gravitational waves

Answer: D) the detection of gravitational waves

Explanation: Weiss, Barish and Thorne. SLO P-11-D-18 · Understanding

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33. Gravitational waves were first directly detected in:

  1. 1990
  2. 1960
  3. 1916
  4. 2015

Answer: D) 2015

Explanation: By LIGO; announced in 2016. SLO P-11-D-18 · Understanding

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34. The mirrors in LIGO hang as pendulums in a vacuum to:

  1. isolate them from vibrations and air disturbances
  2. reflect sound
  3. keep them warm
  4. make them heavier

Answer: A) isolate them from vibrations and air disturbances

Explanation: Noise reduction. SLO P-11-D-21 · Understanding

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35. Gravitational waves open a new 'window' on the universe because:

  1. they reveal events that emit little or no light, like black hole mergers
  2. they replace telescopes entirely
  3. they are slower than light
  4. they are visible to the eye

Answer: A) they reveal events that emit little or no light, like black hole mergers

Explanation: Gravitational-wave astronomy. SLO P-11-D-18 · Understanding

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36. The first detected black hole merger (GW150914) was about:

  1. 1.3 billion light-years away
  2. 8 light-minutes away
  3. 4 light-years away
  4. 100 km away

Answer: A) 1.3 billion light-years away

Explanation: Very distant event. SLO P-11-D-20 · Knowledge

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37. Which carries energy away from an orbiting binary system, making the orbit shrink?

  1. sound waves
  2. gravitational waves
  3. solar wind
  4. magnetic fields

Answer: B) gravitational waves

Explanation: Observed in the Hulse–Taylor binary pulsar. SLO P-11-D-18 · Understanding

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38. Interferometers were used to first detect gravitational waves in:

  1. 1905
  2. 1969
  3. 2000
  4. 2015

Answer: D) 2015

Explanation: LIGO, September 2015. SLO P-11-D-21 · Understanding

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39. Gravitational waves from distant mergers make the Earth's diameter change by about:

  1. 1 centimetre
  2. 1 kilometre
  3. much less than the size of an atomic nucleus
  4. 1 metre

Answer: C) much less than the size of an atomic nucleus

Explanation: Strain sim 10^-21. SLO P-11-D-20 · Knowledge

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40. Gravitational waves are produced when masses:

  1. are cooled
  2. accelerate
  3. move at constant velocity in a straight line
  4. are at rest

Answer: B) accelerate

Explanation: Analogous to accelerating charges making EM waves. SLO P-11-D-18 · Understanding

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41. Gravitational waves distort:

  1. space-time itself, so distances between objects change
  2. only electric fields
  3. only the colour of light
  4. only sound waves

Answer: A) space-time itself, so distances between objects change

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

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42. The 2017 neutron star merger (GW170817) was also observed with:

  1. seismometers only
  2. thermometers
  3. telescopes detecting light (gamma rays, visible, etc.)
  4. sound microphones

Answer: C) telescopes detecting light (gamma rays, visible, etc.)

Explanation: Multi-messenger astronomy. SLO P-11-D-20 · Knowledge

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43. Interferometers make use of the property of light called:

  1. photoelectric effect
  2. dispersion
  3. interference
  4. polarization

Answer: C) interference

Explanation: Superposition of coherent beams. SLO P-11-D-21 · Understanding

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44. A strong source of gravitational waves is:

  1. the Sun at rest
  2. a pair of black holes or neutron stars orbiting each other closely
  3. a light bulb
  4. a car accelerating

Answer: B) a pair of black holes or neutron stars orbiting each other closely

Explanation: Massive, rapidly accelerating binary systems. SLO P-11-D-18 · Understanding

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45. A gravitational wave changes the distance between two mirrors by:

  1. a constant amount
  2. zero always
  3. several metres
  4. a tiny periodic amount

Answer: D) a tiny periodic amount

Explanation: Detected by interferometers. SLO P-11-D-19 · Knowledge

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46. In LIGO, the laser beam is split and sent along:

  1. a circular ring
  2. three parallel arms
  3. two perpendicular arms
  4. one straight arm

Answer: C) two perpendicular arms

Explanation: Michelson interferometer arrangement. SLO P-11-D-21 · Understanding

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47. A passing gravitational wave changes the interference pattern because:

  1. one arm is stretched while the other is squeezed, changing the path difference
  2. the mirrors heat up
  3. the arms rotate
  4. the laser changes colour

Answer: A) one arm is stretched while the other is squeezed, changing the path difference

Explanation: Path difference changes. SLO P-11-D-21 · Understanding

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48. A single star moving at constant velocity:

  1. emits gravitational waves only at night
  2. emits sound waves
  3. emits strong gravitational waves
  4. does not emit gravitational waves

Answer: D) does not emit gravitational waves

Explanation: Acceleration (of a changing mass distribution) is needed. SLO P-11-D-18 · Understanding

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49. Stretching by gravitational waves affects:

  1. only light
  2. only metals
  3. only living things
  4. all objects, including the detector and the Earth

Answer: D) all objects, including the detector and the Earth

Explanation: Space-time itself is distorted. SLO P-11-D-19 · Knowledge

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50. Other gravitational-wave interferometers include:

  1. the LHC
  2. Hubble and Chandra
  3. Virgo (Italy) and KAGRA (Japan)
  4. ISS

Answer: C) Virgo (Italy) and KAGRA (Japan)

Explanation: Global network. SLO P-11-D-21 · Understanding

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