A light beam is travelling from region I to region IV (refer figure) The refractive index in regions I , II , III are n_0,n_0/2,n_0/6 and n_0/8 respectively. The angle of incidence theta for which the beam just misses entering region IV is

A light beam is travelling from region I to region IV (refer figure) T

1.	A light beam is travelling from region I to region IV (refer figure) The refractive index in regions I , II , III are n_0,n_0/2,n_0/6 and n_0/8 respectively. The angle of incidence theta for which the beam just misses entering region IV is
Answer» Solution :As the beam just misses entering the REGION IV, the angle of refraction in the region IV must be `90^@` Application of Snell.s LAW successively at different interfaces give `n_0 SIN theta= n_0/2 sin theta_1= n_0/6 sin theta_2=n_0/8 sin 90^@` `implies sin theta=1/8 or theta= sin^-1 1/8`