Question

When a light ray incidents on the surface of a medium, the reflected ray is completely polarized. Then the angle between reflected and refracted rays is:

• A. 45°
• B. 90°
• C. 120°
• D. 180°

Hint:

Brewster’s angle is given by \( \tan \theta_B = \frac{n_2}{n_1} \), where \( n_1 \) and \( n_2 \) are refractive indices of the media.

Answer 1

The Correct Option is B

Step 1: {Understanding Brewster's Law} 
According to Brewster's law, when light is incident at the Brewster angle, the reflected light is completely polarized.
At this angle, the reflected and refracted rays are perpendicular to each other. 
Step 2: {Derivation of the Perpendicular Relation} 
\[ \theta_{{reflected}} + \theta_{{refracted}} = 90^\circ \] Thus, the angle between the reflected and refracted rays is: \[ \theta = 90^\circ \] Thus, the correct answer is \( 90^\circ \). 
 

Answer 2

Step 1: Understanding Polarization by Reflection
When light is incident on the surface of a transparent medium, and the reflected ray is completely polarized, this situation corresponds to the special case known as Brewster's Angle or Polarizing Angle.

At Brewster's angle \( \theta_B \), the reflected and refracted rays are perpendicular to each other. That is, the angle between them is: \[ \theta_{\text{reflected}} + \theta_{\text{refracted}} = 90^\circ \] This condition ensures that the reflected light is completely polarized with its electric field oscillating perpendicular to the plane of incidence.

Step 2: Brewster’s Law
Brewster's Law states: \[ \tan \theta_B = \frac{n_2}{n_1} \] Where:

• \( \theta_B \) is Brewster's angle,
• \( n_1 \) and \( n_2 \) are the refractive indices of the first and second medium respectively.

However, the critical fact remains that at this angle: \[ \text{Angle between reflected and refracted rays} = 90^\circ \]

 

Final Answer:
Hence, the correct answer is: Option 2: 90°