# Describe how ultrasound waves are used in echo sounding to measure the depth of water beneath a ship.

> AQA GCSE Physics (8463) — 4.6.1 Waves in air, fluids and solids · Describe · 4 marks

## Mark scheme (4 marks)

1. A pulse of ultrasound is emitted (from the ship / downwards into the water)
2. The ultrasound reflects off the seabed (and returns to the ship / is detected by a receiver)
3. The time between transmission and detection of the reflected pulse is measured
4. The depth is calculated using the wave speed and the measured time (with time halved to account for the two-way journey)

## Key terms

- [ultrasound](https://www.gradenine.co.uk/glossary/ultrasound)
- [echo sounding](https://www.gradenine.co.uk/glossary/echo-sounding)

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-ultrasound-waves-are-used-406151cd) · Published by Druglandscape Ltd.