A loudspeaker produces a sound wave that travels through air. Describe the nature of a sound wave, including how energy is transferred and what happens to the air particles as the wave passes through them.

Eduqas A-Level Physics — 2.4 The nature of waves · Describe · 5 marks · View as Markdown

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

Model answer (5 marks)

Sound is a longitudinal wave.

The air particles vibrate parallel to the direction of wave travel, and energy is transferred in that same direction.

As the wave passes, the particles are pushed together, creating compressions.

They are then pulled apart, creating rarefactions.

The particles oscillate about their equilibrium positions and are not permanently displaced; they do not travel with the wave.

Examiner tips

  • Use the term "longitudinal wave" first. Show the particle motion is parallel to wave direction. Mention compressions and rarefactions. State that energy moves with the wave but particles do not.
  • common_mistakes
  • :
  • Calling the wave transverse instead of longitudinal. Forgetting to mention that particles oscillate, not move with the wave. Mixing up the direction of particle motion with the direction of energy transfer.

Mark scheme (5 marks)

  1. Sound is a longitudinal wave
  2. The air particles vibrate parallel to the direction of wave travel / energy transfer
  3. The wave produces compressions (regions where particles are pushed closer together)
  4. The wave produces rarefactions (regions where particles are spread further apart)
  5. Energy is transferred in the direction of wave travel but the air particles are not permanently displaced / do not travel with the wave

Related

More The nature of waves questions

▶ Try answering this question with AI marking (free) →