# Explain how longitudinal waves travel through a medium, referring to compressions and rarefactions. In your answer, also explain why the medium itself does not travel in the direction of the wave.

> AQA A-Level Physics (7408) — 3.3.1 Progressive and Stationary Waves · Explain · 5 marks

## Mark scheme (5 marks)

1. In a longitudinal wave, the oscillations/vibrations of the particles are parallel to (in the same direction as) the direction of travel/energy transfer.
2. Compressions are regions where particles are pushed closer together / regions of higher pressure.
3. Rarefactions are regions where particles are spread further apart / regions of lower pressure.
4. Each particle only oscillates/vibrates about its equilibrium (undisturbed) position / particles do not travel with the wave.
5. The wave (energy) transfers through the medium by each particle passing its disturbance on to the next particle / it is energy that is transferred, not matter.

## Key terms

- [longitudinal wave](https://www.gradenine.co.uk/glossary/longitudinal-wave)
- [compression](https://www.gradenine.co.uk/glossary/compression)
- [rarefaction](https://www.gradenine.co.uk/glossary/rarefaction)

## Related

- [Revision notes for AQA A-Level Physics (7408)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-longitudinal-waves-travel-through-6f030a3e) · Published by Druglandscape Ltd.