A sound wave travelling with a velocity `V` in a medium `A` reaches a point on the interface of medium `A` and medium `B`. If the velocity in the medium `B` be `2 V`, then the angle
of incidence for total internal reflection of the wave will be greater than:

Options

A. `15^(@)`
B. `30^(@)`
C. `45^(@)`
D. `90^(@)`

Answer

B

Explanation

Light travel from medium A with velocity v to medium B with velocity 2v

Velocity is more in medium B , hence it is rarer .
Refractive index of medium A w.r.t. medium B
`mu = ""_(B)mu_(A) = ("Velocity in medium B")/("Velocity in medium A")`
`""_(B)mu_(A) = 2 //1`
Now as `sin C = (1)/(mu) therefore sin C = (1)/(2) = 0 . 5`
`implies C = 30^(@)`