Which of the following conditions are necessary and sufficient for total internal reflection to take place at the boundary between two optical media?

I. Light is passing from optical denser medium to optically less dense medium

II. Light is passing from optically less dense medium to optically denser medium

III. Angle of incidence is greater than a certain critical value

IV. Angle of incidence is lesser than a certain critical value

A. I and II only
B. II only III only
C. III and IV only
D. I and III only

Correct Answer:

Option D = I and III only

Explanation

The conditions for total internal reflection include light traveling from an optically denser medium (higher refractive index) to an optically less dense medium (lower refractive index) and that the angle of incidence is greater than the critical angle.