A microphone connected to an oscilloscope is used to detect a sound wave produced by a tuning fork. The oscilloscope displays a repeating wave pattern. Explain what this tells us about the nature of sound waves, including how energy is transferred and how the particles of the medium behave.

WJEC A-Level Physics (Wales) — 2.4 The nature of waves · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (5 marks)

Sound waves are longitudinal waves.
1. The particles of the medium vibrate parallel to the direction of wave travel.
2. The vibration of the particles carries energy from the tuning fork to the microphone.
3. The particles return to their equilibrium positions after each vibration – the medium itself is not transported.
4. The oscilloscope shows a repeating pattern, indicating the wave is periodic and the vibrations are regular.

Examiner tips

  • Use the term "longitudinal wave" early. Show the link between particle motion and energy transfer. Mention that the medium is not displaced. Highlight the periodic nature shown by the oscilloscope.

Common mistakes

  • Confusing longitudinal with transverse waves. Forgetting that the medium does not move. Describing the wave as non‑periodic or irregular.

Mark scheme (5 marks)

  1. Sound is a longitudinal wave
  2. Particles vibrate parallel to / in the same direction as the direction of energy transfer (wave travel)
  3. The wave transfers energy from the tuning fork to the microphone
  4. The medium (air) is not transferred — particles return to their original/equilibrium positions
  5. The repeating pattern shows the wave is periodic / the vibrations are regular

Key terms in this question

medium

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