Explain how a sound wave is produced by a vibrating loudspeaker and how that sound energy is transferred through the air to reach a listener standing some distance away.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
A loudspeaker cone vibrates, pushing and pulling on the surrounding air molecules. This causes the molecules to move back and forth, creating alternating regions of compression (molecules closer together, higher pressure) and rarefaction (molecules further apart, lower pressure). The disturbance propagates through the air as a longitudinal wave, with the vibration of the particles parallel to the direction of wave travel. Energy is transferred from particle to particle; the air molecules themselves do not travel from the loudspeaker to the listener.
Examiner tips
- Use the word ‘vibrates’ for the cone and ‘compressions/rarefactions’ for the wave pattern.
- Show that the wave is longitudinal and that energy moves through particle‑to‑particle transfer.
- Mention that the molecules do not travel long distances – only the disturbance does.
Common mistakes
- Confusing transverse with longitudinal wave description.
- Saying the air molecules travel from the speaker to the listener instead of the energy transfer.
- Omitting the compression/rarefaction detail.
Mark scheme (4 marks)
- The vibrating loudspeaker cone causes the surrounding air molecules to vibrate / moves air molecules back and forth
- This creates alternating regions of compression (where molecules are closer together / higher pressure) and rarefaction (where molecules are further apart / lower pressure)
- The wave travels through the air as a longitudinal wave, with the direction of particle vibration parallel to the direction of wave travel / energy transfer
- Energy is transferred from particle to particle / the disturbance passes through the medium, but the air molecules themselves do not travel from loudspeaker to listener
Related
- All Eduqas GCSE Physics revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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