# A student says: 'A wave with a higher frequency must have a longer wavelength.' Explain why this statement is incorrect, and describe how frequency and wavelength are actually related when the wave speed stays the same.

> WJEC GCSE Physics (Wales) — 1.5 Features of waves · Explain · 4 marks

> Sound waves travel at approximately 340 m/s through air. A low-pitched sound has a frequency of 85 Hz, while a high-pitched sound has a frequency of 340 Hz.

## Mark scheme (4 marks)

1. Wave speed equals frequency multiplied by wavelength (wave speed = frequency × wavelength)
2. When wave speed is constant, frequency and wavelength are inversely proportional / as one increases the other decreases
3. The low-pitched sound (85 Hz) has a longer wavelength than the high-pitched sound (340 Hz) / correct comparative statement about the two sounds given
4. Therefore the student's statement is wrong because a higher frequency gives a shorter, not longer, wavelength (at constant wave speed)

## Key terms

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

## Related

- [Revision notes for WJEC GCSE 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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-says-a-wave-with-be3512b1) · Published by Druglandscape Ltd.