Question

When a ray is incident on a medium of refractive index $n$ at Brewster's angle, it gets

• A. totally reflected
• B. totally absorbed
• C. circularly polarised
• D. plane polarised

Hint:

At Brewster's angle, the reflected light is completely polarized perpendicular to the plane of incidence.

Answer 1

The Correct Option is D

To solve the question regarding what happens when a ray is incident on a medium at Brewster's angle having a refractive index \(n\), let's consider the following explanation and reasoning:

Understanding Brewster's Angle

Brewster's angle (also known as the polarization angle) is the angle of incidence at which light with a certain polarization is perfectly transmitted through a transparent dielectric surface without any reflection. When light is incident at this angle, the reflected light is perfectly polarized perpendicular to the plane of incidence.

The formula for Brewster's angle \(\theta_B\) is given by:

\(\tan \theta_B = n\)

where \(n\) is the refractive index of the medium.

Explanation of Options

• Totally Reflected: This option is incorrect because at Brewster's angle, the reflected light is not totally reflected, but rather it is partially reflected and fully polarized.
• Totally Absorbed: This is incorrect because no absorption is relevant in terms of Brewster's angle; the phenomenon is about reflection and polarization.
• Circularly Polarised: This option is incorrect because Brewster's angle specifically results in plane polarization of the reflected light.
• Plane Polarised: This is the correct answer. At Brewster's angle, the reflected light is completely plane polarized perpendicular to the plane of incidence.

Conclusion

The correct answer is that when a ray is incident on a medium at Brewster's angle, it gets plane polarised.