Question

You are provided with a narrow and parallel beam of light. State how you will determine experimentally, whether it is a beam of ordinary(unpolarised) light, partially polarised light or completely polarised light.

Answer 1

To detect the given light is passed through a polarised and it is rotated about the incident light:

$\left(1\right)$ If on rotating the polaroid through are complete rotation, there is no change in the intensity of the emergent light, then the given light is unpolarised,

$\left(2\right)$ If there is a change in the intensity of emergent light in one complete rotation of the polaroid, the intensity becomes twice maximum and twice zero, then the given light is completely plane-polarised,

$\left(3\right)$ If the intensity of emergent light changes but never becomes zero, then the given light is partially polarised.