Question

A light is incident on a surface having refractive index $ \frac{4}{3} $ and reflected light is completely polarised. $ \left( \tan 53^\circ = \frac{4}{3} \right) $. What is the angle of incidence?

• A. \( 53^\circ \)
• B. \( 42^\circ \)
• C. \( 63^\circ \)
• D. \( 30^\circ \)

Hint:

To find the angle of incidence for complete polarisation, use Brewster's law: \( \tan \theta_B = \frac{n_2}{n_1} \), where \( n_1 \) is the refractive index of the first medium and \( n_2 \) is that of the second medium.

Answer 1

The Correct Option is A

When light is incident on a surface and the reflected light is completely polarised, the angle of incidence is equal to the Brewster angle. The Brewster angle \( \theta_B \) is given by the formula: \[ \tan \theta_B = \frac{n_2}{n_1} \] where \( n_1 \) is the refractive index of the medium from which the light is coming (air, which is approximately 1), and \( n_2 \) is the refractive index of the surface (in this case, \( \frac{4}{3} \)). We are given that: \[ \tan \theta_B = \frac{4}{3} \] Therefore, the angle of incidence is: \[ \theta_B = 53^\circ \]
Thus, the correct answer is \( 53^\circ \).