A sound wave travels from air to water. The angle of incidence is `alpha_1`, and the angle of reflection is `alpha_2`. If the Snell.s law is valid, then ......

Options

A. `alpha_1 = alpha_2`
B. `alpha_1 gt alpha_2`
C. `alpha_1 lt alpha_2`
D. None of these

Answer

A, B, C

Explanation

Angle of incident i = `alpha_1`
Angle of reflection r = `alpha_2`
Here Snell.s law will be obeyed.
`therefore n_A sin alpha_1=n_w sin alpha_2`
`therefore (sinalpha_1)/(sin alpha_2)=(n_w)/(n_A)`….......(1)
Now `(n_w)/(n_A)=(C//v_w)/(C//v_A)=(v_w)/(v_A) lt 1`
`v_A lt v_w` .......(2)
(The velocity of sound in water is more than th velocity of sound in air)
From equation (1) and (2),
`(sin alpha_1)/(sin alpha_2) lt 1 = sin alpha_1 lt sin alpha_2`
`therefore alpha_1 lt alpha_2` (sin function is increasing function)