A point source is placed at a depth h below the surface of water (refractive index = μ).

(a) Show that light escapes through a circular area on the water surface with its center directly above the point source.

(b) Find the angle subtended by a radius of the area on the source.

(a) Let x= radius of the circular area

S be the point source

H is the depth

Critical angle=

So,

⇒

⇒ (since,)

⇒

⇒

So, clearly from the fig., light escapes from the circular area at a fixed desistance r on the water surface, directly above the point source S.

(b) The angle subtended by a radius of the area on the source S

⇒

1