The perpendicular at a point of contact to the tangent to a circle passes through the centre.

Options

A. For a particular orientation there shall be darkness as observed through the polaroid.
B. The intensity of light as seen through the polaroid shall be independent of the rotation.
C. The intensity of light as seen through the polaroid shall go through a minimum but not zero for two orientations of the polaroid.
D. The intensity of light as seen through the polaroid shall go through a minimum for four orientations of the polaroid.

Answer

C

Explanation

The intensity of light as seen through the polaroid shall go through a minimum but not zero for two orientations of the polaroid.
Here, a ray of light is made incident on the glass slab with angle of incidence equal to angle of polarisation and so reflected light ray will be completely plane polarised but refracted and transmitted light rays are partially plane polarised in which majority `vecE` vectors (light vectors) are mutually parallel and remaining `vecE` vectors are equally distributed in all directions. Hence, when a polaroid placed in the path of transmitted light ray, is given one full rotation, for two positions of its optic axis (pass axis)
when majority `vecE` vectors become perpendicular to optic axis, there are few `vecE` vectors which are parallel to optic axis and so they can pass through polaroid. Hence for these two positions of optic axis, intensity of transmitted light will be non-zero and minimum. Thus option (C) is correct.