AQA GCSE Physics

Revision Notes

6.1.12 Echo Sounding

Higher Tier Only

Echo Sounding

  • 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?


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

Exam Tip

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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Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.

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