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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 °