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Nicol Prism
A nicol prism is an optical device which is used for producing plane polarised light and analysing light the same .
The nicol prism consists of two calcite crystal cut at 68 ° with its principal axis joined by a glue called Canada balsam .
Law of Malus
When a beam of completely plane polarised light is incident on an analyser , the intensity of transmitted light from analyser is directly proportional to the square of the cosine of the angle between plane of transmission of analyser and polariser , i . e .,
I ∝ cos 2 θ
When ordinary light is incident on a polariser the intensity of transmitted light is half of the intensity of incident light .
When a polariser and analyser are perpendicular to each other , then intensity of transmitted light from analyser becomes O .
Brewster ’ s Law
When unpolarised light is incident at an angle of polarisation ( i p ) on the interface separating air from a medium of refractive index μ , then reflected light becomes fully polarised , provided
μ = tan i p
If angle of polarisation is i p and angle of refraction is μ then i p + r = 90 °