An unpolarized light beam travelling in air is incident on a medium of refractive index 1.73 at Brewster's angle. Then:

Question

An unpolarized light beam travelling in air is incident on a medium of refractive index 1.73 at Brewster's angle. Then:

1. A. Reflected light is completely polarized and the angle of reflection is close to 60^ (Correct answer)
2. B. Reflected light is partially polarized and the angle of reflection is close to 30^
3. C. Both reflected and transmitted light are perfectly polarized with angles of reflection and refraction close to 60^ and 30^, respectively
4. D. Transmitted light is completely polarized with angle of refraction close to 30^

Correct Answer

Option A — Reflected light is completely polarized and the angle of reflection is close to 60^

Detailed Solution & Explanation

The correct answer is Option A.

Key Points

• Brewster's law: $\mu=\tan\theta_B$, so $\tan\theta_B=1.73=\sqrt{3}\Rightarrow\theta_B=60^\circ$.
• At the Brewster (polarising) angle the reflected light is completely (perfectly) polarized.
• The angle of reflection equals the angle of incidence $=\theta_B=60^\circ$.
• The transmitted (refracted) light is only partially polarized.