(a)[1]
Sound waves are longitudinal waves. With reference to the direction in which energy is propagated, state what is meant by a longitudinal wave.
(b)
A stationary sound wave in air has amplitude $A$. In an experiment, a detector is used to find $A^2$. Fig. 4.1 shows how $A^2$ varies with distance $x$ along the wave.
(b(i))[1]
State the phase difference between the vibrations of an air particle at $x = 25\,\text{cm}$ and those of an air particle at $x = 50\,\text{cm}$.
(b(ii))[3]
The speed of sound in air is $330\,\text{m s}^{-1}$. Determine the frequency of the sound wave.
(b(iii))[2]
Determine the ratio $\dfrac{\text{amplitude } A \text{ of wave at } x = 20\,\text{cm}}{\text{amplitude } A \text{ of wave at } x = 25\,\text{cm}}$.