Q.Distinguish between unpolarized light and plane polarized light. How does a single polaroid convert one into the other?

In unpolarized light -- ordinary light from the Sun or an incandescent lamp -- the oscillating electric field, at any given instant, has components in every direction perpendicular to the propagation direction, and the actual direction of vibration itself changes randomly and very rapidly, since the light is the combined, uncorrelated output of an enormous number of independently-emitting atoms.

In plane polarized light, by contrast, the electric field vibrates only within one single, fixed plane (the plane of vibration) that contains the direction of propagation -- there is a definite, unchanging direction of vibration. …

Contrast the random, all-direction vibration of unpolarized light with the single fixed direction of plane polarized light, then explain …

• Saying a polaroid 'blocks' light of certain colours (that is a colour filter, not a polaroid, which acts on the DIRECTION of vibration, not wavelength). …