Question

A ray of light strikes a piece of glass at an angle of incidence of 60° and the reflected beam is completely plane polarised. The refractive index of glass is:

• A. \( \sqrt{2} \)
• B. \( \sqrt{3} \)
• C. \( \sqrt{5} \)
• D. \( \sqrt{3} \)

Hint:

At Brewster's angle, the angle of incidence leads to total polarization of the reflected light. Use the formula \( n = \tan(\theta_B) \) to find the refractive index.

Answer 1

The Correct Option is B

Step 1: Brewster’s law
At Brewster’s angle, the reflected light is completely plane-polarized. The relation between Brewster’s angle and refractive index is:
\( \tan \theta_B = n \)

Step 2: Substitute given value
Given:
\( \theta_B = 60^\circ \)

So, \[ n = \tan 60^\circ \] \[ n = \sqrt{3} \]

Final Answer:
\( n = \sqrt{3} \)