Question

A Sound wave travels from air to water. The angle of incidence is α₁ and the angle of reflection is α₂ If the snell’s Law is valid then,

(A) α₁ ≥ α₂

(B) α₁ = α₂

(C) α₁ > α₂

(D) α₁ < α₂

Answer 1

The correct option is  (D) α₁ < α₂

Explanation:

aη_w = [(sin i) / (sin r)] = [(sin α₁) / (sin α₂)] ....(1)

also  aη_w = (v_a / v_w)

= [(velocity of sound in air) / (velocity of sound in water)]

as  v_w > v_a

hence (v_a / v_w) < 1

i.e.      aη_w < 1

From (1) [(sin α₁) / (sin α₂)] < 1

sin α₁ < sin α₂    

i.e. α₁ < α₂.