When a continuous sinusoidal wave passes from Medium X into Medium Y
PHYSICS · Single correct · A Level · Physics · Waves · Waves
Problem
When a continuous sinusoidal wave passes from Medium X into Medium Y, the wave’s speed decreases while its frequency remains the same. Which statement best explains why the wavelength becomes shorter in Medium Y?
(a) Because the wave’s frequency drops in Medium Y, fewer crests are produced each second, so the wavelength shortens.
(b) Because Medium Y is denser, it compresses the wavefronts, forcing the crests closer together and shortening the wavelength.
(c) Because the wave moves more slowly, it travels a smaller distance during one period (T=1/f), so the wavelength λ=vT is shorter.
(d) Because the wave loses energy and amplitude on entering Medium Y, the wavelength decreases to conserve energy.