Waves problem-solving question

A water wave has wavelength 0.80 m and frequency 2.5 Hz. (a) Calculate the wave speed. [3] (b) Calculate the time for 15 waves to pass a point. [2] (c) State the effect on wave speed if the frequency increases but the wave continues in the same water depth. [2]

(a) v = f lambda = 2.5 x 0.80 = 2.0 m/s. (b) 15 waves at 2.5 each second take 15/2.5 = 6.0 s. (c) Wave speed stays the same in the same medium; wavelength decreases when frequency increases.

Award equation, substitution and 2.0 m/s; division and 6.0 s; one mark each for same speed and wavelength adjustment.

Use v = f lambda. Frequency tells you waves per second.