Describe how ultrasound waves are used in echo sounding to measure the depth of water beneath a ship.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
A pulse of ultrasound is emitted from the ship downwards into the water.
The pulse reflects off the seabed and returns to the ship where it is detected by a receiver.
The time between transmission and detection of the reflected pulse is measured.
The depth is calculated using the wave speed and the measured time, with the time halved to account for the two‑way journey.
The pulse reflects off the seabed and returns to the ship where it is detected by a receiver.
The time between transmission and detection of the reflected pulse is measured.
The depth is calculated using the wave speed and the measured time, with the time halved to account for the two‑way journey.
Examiner tips
- Use the exact phrase "pulse of ultrasound is emitted" and "reflected pulse is detected". Show the calculation step: depth = (speed × time)/2. Mention the speed of sound in water (~1500 m s⁻¹).
- Keep the answer concise – 4 points, no extra explanation.
Mark scheme (4 marks)
- A pulse of ultrasound is emitted (from the ship / downwards into the water)
- The ultrasound reflects off the seabed (and returns to the ship / is detected by a receiver)
- The time between transmission and detection of the reflected pulse is measured
- The depth is calculated using the wave speed and the measured time (with time halved to account for the two-way journey)
Key terms in this question
Related
- All AQA GCSE Physics (8463) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →