Four ray 1,2,3 and 4 are incident normally on the face P   Q of an isosceles prism P   Q   R with apex angle ∠ Q = 120 ° . The refractive indices of the material of the prism for the above rays 1,2,3 and 4 are 1.85 , 1.95,2.05 and 2.15 respectively and the surrounding medium is air. Then, the rays emerging from the face Q   R are

Step-by-step solution

Total internal, reflection occurs when n ≥ 1 sin i c In given situation, angle of incidence of each of ray is 30 ° over face P R . So , i = 30 ° ⇒ 1 sin i = 1 sin 30 ° = 2 Hence, for total internal reflection at surface P R , n ≥ 2 . As refractive index for 3 and 4 is more than 2 , only rays 1 and 2 , pass from face P R while rays 3 and 4 pass through face Q R (as shown in diagram).