A glass vessel in the shape of a triangular prism is filled with water, and light is incident normally on the face xy. If the refractive indices for water and glass are `4//3` and `3//2` respectively, total internal reflection will occur a the glass-air surface xz only for `sin theta` greater than
A `1//2`
B `2//3`
C `3//4`
D `8//9`
E `16//27`

Answer

C

Explanation

`i=theta_C`
`:. sini=sin theta_C=1/mu_g=2/3`
Applying Snell's law at point A,
we have
`mu_w sin theta=mu_g sini`
`:. 4/3 sin theta=3/2xx2/3`
`:. sin theta=3/4`