Discuss the construction of nicol prism and how it is used as an analyser
Answers
Nicol prism is an optical device which is used for
producing and analyzing plane polarized light in
practice.
Principal :- Nicol Prism is based upon phenomenon of Double refraction.
Construction:-
• It is constructed from the calcite crystal PQRS having length three times of its
width.
• Its end faces PQ and RS are cut such that the angles in the principal section
become 68° and 112° in place of 71° and 109°
• The crystal is then cut diagonally into two parts. The surfaces of these parts are
grinded to make optically flat and then these are polished.
• Thus polished surfaces are connected together with a special cement known as
Canada Balsam
Working:-
In order to produce and analyse the plane polarised light, we
arrange two nicol prisms.
• When a beam of unpolarised light is incident on the nicol prism,
emergent beam from the prism is obtained as plane polarised, and
which has vibrations parallel to the principal section.
• This prism is therefore known as polariser. If this polarised beam
falls on another parallel nicol prism P2, whose principal section
is parallel to that of P1, then the incident beam will behave as Eray inside the nicol prism P2 and gets completely transmitted
through it.
• This way the intensity of emergent light will be maximum.