Question

On a hypotenuse of a right angled prism of liquid is placed as shown in the figure. Light is allowed to fall normally on the short face of the prism. In order that the ray of light may be totally reflected, the maximum value of refractive index is 

• A. 1.30
• B. 1.47
• C. 1.20
• D. 1.25

Hint:

Total internal reflection occurs only when light travels from denser to rarer medium.

Answer 1

The Correct Option is B

Step 1: For total internal reflection, sin c = (1)/(μ)
Step 2: From prism geometry, the angle of incidence at the hypotenuse is fixed.
Step 3: Maximum μ corresponds to the critical condition.