# Explain why sound waves are described as longitudinal waves and how they are able to travel through air.

> Eduqas GCSE Physics — 5.1 Waves in air, fluids and solids · Explain · 4 marks

## Mark scheme (4 marks)

1. In a longitudinal wave, the particles vibrate/oscillate parallel to the direction of energy transfer (or direction of wave travel)
2. The vibrating source causes air particles to be pushed together, forming compressions, and pulled apart, forming rarefactions
3. These compressions and rarefactions travel through the air, transferring energy
4. Sound requires a medium (a material/particles) through which to travel and cannot travel through a vacuum

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-sound-waves-are-described-024a92d5) · Published by Druglandscape Ltd.