(a)[3]
Describe an experiment that demonstrates that a medium is needed to transmit sound waves. You may include a labelled diagram if you wish.
(b)[2]
When a sound wave moves through air or water, the molecules in the air or water move. Describe the motion of the molecules caused by the sound wave.
(c)[1]
Describe what is meant by the term ‘a rarefaction’.
(d)[2]
Fig. 4.1 shows a dolphin. The dolphin can hear sound frequencies from 75 Hz to 140 000 Hz. In water, sound travels at $1500\,\text{m s}^{-1}$. Calculate the shortest wavelength of sound in water that the dolphin can hear.