A sound wave and a light wave are reflected and refracted (or transmitted) from water surface. Show the changes in different physical quantities associated with a wave.

Answer

A

Explanation

Sound wave We have seen in article 18.6, that water is a rarer medium for sound. When a wave travels from a denser to rarer medium, it bends away from normal. Its speed, wavelength and amplitude increase but angular wave number decreases. Further, in reflection from a rarer medium and in transmission there is no change in phase angle.
In the figure shown, 1 is incident wave 2 is reflected wave and 3 is transmitted wave.

`alpha=beta, gamma gt alpha, f_(1)=f_(2)=f_(3),v_(1) =v_(2) , lambda_(1) = lambda_(2), k_(1) = K_(2), v_(1) lt v_3, lambda_3 gt lambda_1 = lambda_2, k_3ltk_1`
`Deltaphi_(12) = Deltaphi_(13)=0^@`.
Electromagnetic wave For electromagnetic wave, water is denser medium. So, in water, ray
of light will bend towards normal.

Further, speed and wavelength in this medium will decrease. But value of k will increase.
`alpha = beta, gamma lt alpha, f_1 = f_2 = f_3 , v_1 =v_2, lambda_1 = lambda_2, k_1=k_2, v_3 lt v_1, lambda_3 lt lambda_1, k_3 gt k_1`
`Deltaphi_(12) = pi` and `Delta phi_(13) = 0^@`