Question: 28. An unpolarised light beam strikes a glass surface at Brewster’s angle Then
(1) the reflected light will be partially polarised.
(2) the refracted light will be completely polarised.
(3) both the reflected and refracted light will be completely polarised.
(4) the reflected light will be completely polarised but the refracted light will be partially polarised.
Answer: Option (4)
Explanation:
Brewster’s angle is the angle of incidence at which the reflected light is completely plane polarised.
At Brewster’s angle, the reflected and refracted rays are perpendicular to each other.
The condition for Brewster’s angle is given by
\tan \theta_B = \muWhen unpolarised light is incident at Brewster’s angle,
vibrations parallel to the plane of incidence are not reflected.
As a result, the reflected light contains vibrations only perpendicular to the plane of incidence.
Hence, the reflected light becomes completely polarised.
The refracted light still contains components in both perpendicular and parallel directions.
Therefore, the refracted light is only partially polarised.
Thus, the correct answer is Option (4).