AS Level Physics chapter 7: Waves MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

109 exam-style questions on Waves, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

109 questions · 5 topics · 10 per test

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What chapter 7 covers

Ten Waves questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. A source of frequency 400 Hz moves directly towards a stationary observer at 20 m s−1. The speed of sound is 340 m s−1. What is the wavelength of the sound reaching the observer?

  1. A
    0.80 m
  2. B
    0.85 m
  3. C
    0.90 m
  4. D
    1.2 m
Show answer

Answer: A. Ahead of the source each wave is squeezed into (v − vs)/fs = 320 ÷ 400 = 0.80 m. 0.85 m is the wavelength from a stationary source; 0.90 m is behind the moving source.

2. Which statement is correct for a longitudinal wave?

  1. A
    the oscillations are perpendicular to the direction of energy transfer
  2. B
    the oscillations are parallel to the direction of energy transfer
  3. C
    it cannot travel through a gas
  4. D
    it can be polarised
Show answer

Answer: B. In a longitudinal wave (sound) particles oscillate along the direction of travel, forming compressions and rarefactions. Only transverse waves can be polarised.

3. In a sound wave of frequency 425 Hz, the distance from the centre of a compression to the centre of the nearest rarefaction is 0.40 m. What is the speed of the sound?

  1. A
    85 m s−1
  2. B
    170 m s−1
  3. C
    340 m s−1
  4. D
    680 m s−1
Show answer

Answer: C. Compression to nearest rarefaction is half a wavelength, so λ = 0.80 m and v = 425 × 0.80 = 340 m s−1. Taking 0.40 m as λ gives 170 m s−1.

4. Which can be made to carry either a transverse wave or a longitudinal wave?

  1. A
    light in a vacuum
  2. B
    sound in air
  3. C
    radio waves
  4. D
    a stretched slinky spring
Show answer

Answer: D. A slinky can be shaken sideways (transverse) or pushed along its length (longitudinal). Sound in air is only longitudinal; light and radio waves are only transverse.

5. A wave has a period of 4.0 ms. What is its frequency?

  1. A
    4.0 Hz
  2. B
    25 Hz
  3. C
    250 Hz
  4. D
    4000 Hz
Show answer

Answer: C. f = 1/T = 1 ÷ 4.0 × 10−3 = 250 Hz.

6. In a longitudinal wave, what is the distance between the centres of two adjacent compressions?

  1. A
    one wavelength
  2. B
    half a wavelength
  3. C
    the amplitude
  4. D
    two wavelengths
Show answer

Answer: A. Adjacent compressions are one complete cycle apart, which is one wavelength. A compression and the next rarefaction are half a wavelength apart.

7. A siren emitting a constant frequency accelerates directly towards a stationary observer, always moving slower than sound. How does the frequency heard by the observer change with time?

  1. A
    it is constant and higher than the source frequency
  2. B
    it decreases steadily
  3. C
    it increases steadily
  4. D
    it is equal to the source frequency
Show answer

Answer: C. The observed frequency fsv/(v − vs) rises as vs rises, so as the siren speeds up the pitch heard keeps rising.

8. For a transverse wave, a displacement–distance graph shows exactly two complete wavelengths over 1.6 m. A displacement–time graph for one point shows exactly 5 complete cycles in 0.10 s. What is the wave speed?

  1. A
    4.0 m s−1
  2. B
    16 m s−1
  3. C
    40 m s−1
  4. D
    80 m s−1
Show answer

Answer: C. λ = 1.6 ÷ 2 = 0.80 m and f = 5 ÷ 0.10 = 50 Hz, so v = 50 × 0.80 = 40 m s−1. Using 1.6 m as λ gives 80 m s−1.

9. Which statement applies to all electromagnetic waves?

  1. A
    they are transverse and travel at 3.00 × 108 m s−1 in free space
  2. B
    they are longitudinal waves
  3. C
    they need a medium to travel through
  4. D
    they all have the same frequency
Show answer

Answer: A. All electromagnetic waves are transverse and travel at the same speed c in a vacuum. They differ in frequency and wavelength.

10. Why can sound not travel through a vacuum, although light can?

  1. A
    sound is a transverse wave
  2. B
    light is a longitudinal wave
  3. C
    sound is a mechanical wave and needs particles of a medium to oscillate
  4. D
    sound travels faster than light
Show answer

Answer: C. Sound is passed on by particles of a medium pushing on their neighbours. Light is an electromagnetic wave and needs no medium.

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Ways to practise this chapter

Waves: questions students ask

How many Waves MCQs are there?

109, each with the answer and a short explanation, across 5 topics: Progressive waves, Transverse and longitudinal waves, Doppler effect for sound waves, Electromagnetic spectrum, Polarisation. Every chapter test draws ten of them, so you can take it many times.

Is the AS Level Physics chapter 7 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

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