Engineering Physics

14.18 Nicol prism

Nicol prism is an optical device used to produce and analyse plane polarized light. This was invented by William Nicol in the year 1828. Nicol prism is made from a double refracting calcite crystal. As shown in Fig. 14.28, a calcite crystal whose length is three times its breath is taken. The corners A′G′ is blunt and A′C G′E is the principal section with ∠A′CG′ = 71°. The end faces A′BCD and EFG′H are grounded so that the angle ACG = 68°. The crystal is cut along the plane AKGL. The cut surfaces are polished untill they are optically flat and cemented together with Canada balsam.

The refractive index of Canada balsam (1.55) is in between the refractive indices of ordinary (1.658) and extraordinary (1.486) rays in calcite crystal. ...