GCSEPhysicsAQARevision NotesWavesWaves in Air, Fluids & SolidsEcho Sounding

Echo Sounding (AQA GCSE Physics): Revision Note

Exam code: 8463

Written by: Ashika

Reviewed by: Caroline Carroll

Updated on 2 July 2026

Echo Sounding

Higher Tier Only

Echo sounding uses ultrasound to detect objects underwater
The sound wave is reflected off the ocean bottom
The time it takes for the sound wave to return is used to calculate the depth of the water
The distance the wave travels is twice the depth of the ocean
- This is the distance to the ocean floor plus the distance for the wave to return

Echo Sounding, downloadable IGCSE & GCSE Physics revision notes

Echo sounding is used to determine water depth

Worked Example

The sound wave released from a ship took 0.12 seconds to return. The speed of sound in water is 1500 m/s.

What was the depth of the sea?

Answer:

Step 1: List the known quantities

Wave speed, v = 1500 m/s
Time, t = 0.12 s

Step 2: Write out the wave speed, distance and time formula

Step 3: Rearrange the equation to make distance (x) the subject

x = v × t

Step 4: Put known values into the equation

x = 1500 × 0.12 = 180 m

Step 5: Half the distance to obtain the depth

d = 180 ÷ 2

Depth, d = 90 m

Examiner Tips and Tricks

Don't forget to take into account that the sound wave has travelled twice the distance.

You can do this one of two ways:

Halve the time at the beginning, or
Halve the distance at the end

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