Question

When unpolarized light is incident at an angle of 60° on a transparent medium from air. The reflected ray is completely polarized. The angle of refraction in the medium is

• A. 30°
• B. 60°
• C. 90°
• D. 45°

Answer 1

The Correct Option is A

To determine the angle of refraction when unpolarized light strikes a transparent medium at 60° and results in a completely polarized reflected ray, we apply Brewster's Law. Brewster's Law establishes that the tangent of the polarizing angle (\(\theta_B\)) equals the medium's refractive index (\(n\)):

\(\tan(\theta_B) = n\)

In this scenario, the angle of incidence (\(\theta_B\)) is 60°.

Brewster's Law also dictates that when light is incident at the polarizing angle, the reflected ray is polarized perpendicularly to the plane of incidence.

Snell's Law relates the angle of incidence (\(\theta_i\)) and the angle of refraction (\(\theta_r\)) to the refractive index (\(n\)):

\(\sin(\theta_i) = n \cdot \sin(\theta_r)\)

When the reflected light is fully polarized, the angle of incidence (\(\theta_B = 60°\)) and the angle of refraction (\(\theta_r\)) are complementary:

\(\theta_B + \theta_r = 90°\)

This leads to:

\(\theta_r = 90° - \theta_B\)

Substituting the given angle of incidence:

\(\theta_r = 90° - 60° = 30°\)

The angle of refraction is 30°.

The final answer is 30°.