Question

Plane polarized light is passed through a Polaroid. Now the Polaroid is given one complete rotation about the direction of light propagation. When viewed through another Polaroid (analyser), one of the following is observed:

• A. The intensity of light gradually decreases to zero and then remains zero
• B. The intensity of light becomes twice maximum and twice zero
• C. The intensity of light becomes maximum and stays maximum
• D. The intensity of light does not change

Answer 1

The correct option is B The intensity of light becomes twice maximum and twice zero

The Intensity of light coming out of a polaroid is
given by $I=I_{0}co{s}^2\theta$
when $\theta$ is changed to $\theta +2\pi$ by rotation
$co{s}^2\theta$ becomes 1 twice at $\pi$ and $2\pi$ and
o twice at $\pi /2$ and $3\pi /2$
Thus option B is correct.