Question

8. A straight vibrator causes water ripples to travel across the surface of a shallow tank. The

waves travel a distance of 33 cm in 1.5 s, and the distance between successive wave

crests is 4.0 cm. What is the frequency of the vibrator? (2 marks)

Answer 1

The frequency is wave speed divided by wavelength. The speed of the wave is

$$v=\frac{d}{t}=\frac{0.33}{1.5}=0.22\text{ m/s}.$$

The wavelength can be calculated from the distance between two succeeding crests: 0.04 m.

Hence, the frequency of the wave, which is equal to the frequency of the vibrator, is

$$f=\frac{v}{\lambda}=\frac{0.22}{0.04}=5.5\text{ Hz}.$$