A fishing boat uses sonar to measure the depth of the sea.
The sonar sends a pulse of ultrasound down to the seabed and detects the echo.
The echo is detected 0.24 s after the pulse is sent.
The speed of ultrasound in sea water is 1500 m/s.
Calculate the depth of the sea below the boat.
The ultrasound has a frequency of 50 kHz50\ \text{kHz}50 kHz.
Calculate the wavelength of the ultrasound in sea water.
Give one reason why ultrasound is used rather than audible sound.
The boat moves to a new position. The echo now takes a longer time to return.
State what this shows about the sea at the new position.
112 exam-style questions on Edexcel GCSE Physics 4.3 Sound, ultrasound and infrasound, covering 4.3.1 Sound waves, vibrations and the human ear, 4.3.2 Ultrasound and infrasound, 4.3.3 Uses of ultrasound and infrasound, and 4.3.4 Sound waves passing between media. Each one has a worked solution and a mark scheme showing where the marks go.