Question

How will you identify with the help of an experiment whether a given beam of light is of polarized light or of unplolarised light?

Answer 1

To indentify whether a given beam of light is polarized or unpolarised it is passed through a polaroid and polaroid is rotated about the incident light.
(1) If on rotating the polaroid through one complete rotation, there is no changes in the intensity of emergent light in any position, then the given light is unpolarised.
(2) If there is a changes in the intensity of emergent light in one complete rotation of the polaroid the intensity becomes twice the maximum and twice zero then the given light is completely plane polarised.
(3) If the intensity of the emergent light changes but never becomes zero, then the given light is partially polarised.