Bats find insects by sending out pulses of ultrasound and detecting the echoes.
A bat sends out a pulse of ultrasound with a frequency of 40 kHz40\ \text{kHz}40 kHz.
The speed of sound in air is 340 m/s.
Calculate the wavelength of the ultrasound.
The echo from a moth returns to the bat 0.020 s after the pulse is sent.
Calculate the distance between the bat and the moth.
Explain why a person standing near the bat cannot hear the pulse.
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.