(a)[1]
Describe one distinction between a compression and a rarefaction.
(b(i))[1]
In a specified medium, the speed of both audible sound and ultrasound waves is $v$. State the equation that connects the wavelength $\lambda$ of a sound wave with its frequency $f$.
(b(ii))[1]
Explain how the wavelength of an audible sound wave compares with that of an ultrasound wave in this medium.
(c)[2]
Describe one use of ultrasound waves.