Question

Critical angle for total internal reflection of light of a certain frequency at a denser-rarer boundary is 30°. At what angle should the same light be incident on the boundary from the side of denser medium that the reflected and the refracted rays are mutually perpendicular?

• A. tan^–1 (2)
• B. tan^–1$\left( \frac { 1 } { 3 } \right)$
• C. cos^–1$\left( \frac { 2 } { \sqrt { 5 } } \right)$
• D. cos^–1$\left( \frac { 1 } { \sqrt { 5 } } \right)$

Answer 1

Answer: (C)

cos^–1$\left( \frac { 2 } { \sqrt { 5 } } \right)$

Answer 2

$\frac { 1 } { 2 }$

m = 2

2 sin i = 1. sin (90⁰ – i)

tan i = $\frac { 1 } { 2 }$

Ž cos i = $\left( \frac { 2 } { \sqrt { 5 } } \right)$