(a) Sound waves are longitudinal waves. By reference to the direction of propagation of energy, 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 determine A². The variation of A² with distance x along the wave is shown in Fig. 4.1. [Figure 4.1]

1. (a)Sound waves are longitudinal waves. By reference to the direction of propagation of energy, state what is meant by a longitudinal wave.[1]
2. (b)(i)State the phase difference between the vibrations of an air particle at x = 25 cm and the vibrations of an air particle at x = 50 cm. phase difference = °[1]
3. (b)(ii)The speed of the sound in the air is 330 ms⁻¹. Determine the frequency of the sound wave. frequency = Hz[3]
4. (b)(iii)Determine the ratio amplitude A of wave at x = 20 cm -------------------------------------------------------------- amplitude A of wave at x = 25 cm ratio = [2]

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