1. A Nicol prism is a type of polarizer. It is an optical device made from calcite crystal used to convert ordinary light into plane polarized light. It is made in such a way that it eliminates one of the rays by total internal reflection, i.e. the ordinary ray is eliminated and only the extraordinary ray is transmitted through the prism. It was the first type of polarizing prism, invented in 1828 by William Nicol (1770–1851) of Edinburgh. == Mechanism == The Nicol prism consists of a rhombohedral crystal of Iceland spar (a variety of calcite) that has been cut at an angle of 68° with respect to the crystal axis, cut again diagonally, and then rejoined, using a layer of transparent Canada balsam as a glue. Unpolarized light ray enters through the side face of the crystal, and is split into two orthogonally polarized, differently directed rays by the birefringence property of calcite. The ordinary ray, or o-ray, experiences a refractive index of no = 1.658 in the calcite and undergoes a total... from wikipedia.org