# A student claps their hands once whilst standing a large distance from a tall cliff face. They hear an echo a short time later. Explain how the student could use this situation to determine the speed of sound in air, and state why the distance used in the calculation must be twice the distance between the student and the cliff.

> Pearson Edexcel International GCSE Physics (4PH1) — 3.3 Light and sound · Explain · 4 marks

## Mark scheme (4 marks)

1. Measure the distance between the student and the cliff face
2. Measure the time between the clap and the echo being heard
3. Use speed = distance / time to calculate the speed of sound
4. The sound must travel to the cliff and back, so the total distance travelled by the sound is twice the distance between the student and the cliff

## Key terms

- [echo](https://www.gradenine.co.uk/glossary/echo)
- [speed of sound](https://www.gradenine.co.uk/glossary/speed-of-sound)

## Related

- [Revision notes for Pearson Edexcel International GCSE Physics (4PH1)](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-student-claps-their-hands-once-76f247d1) · Published by Druglandscape Ltd.