# A sound wave travels through air. The sound wave has a wavelength of 0.85 m and a wave speed of 340 m/s. Explain what is meant by the terms 'wavelength', 'frequency', and 'wave speed', and state the relationship between these three quantities.

> WJEC A-Level Physics (Wales) — 2.5 Wave properties · Explain · 5 marks

> Sound waves are longitudinal waves that transfer energy through the air without transferring matter.

## Mark scheme (5 marks)

1. Wavelength is the distance from one point on a wave to the next identical point (e.g. crest to crest or compression to compression)
2. Frequency is the number of complete waves (cycles) passing a point per second
3. Wave speed is the distance travelled by the wave per second (or the speed at which the wave front moves through the medium)
4. Wave speed = frequency × wavelength (v = f × λ)
5. Correct application of the relationship: as frequency increases, wavelength decreases (for a constant wave speed) OR correct identification that frequency and wavelength are inversely proportional at constant speed

## Key terms

- [wavelength](https://www.gradenine.co.uk/glossary/wavelength)
- [frequency](https://www.gradenine.co.uk/glossary/frequency)
- [wave speed](https://www.gradenine.co.uk/glossary/wave-speed)

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](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/a-sound-wave-travels-through-air-2825b33a) · Published by Druglandscape Ltd.