Discuss about pile of plates.

Explanation

(i) The phenomenon of polarisation by reflection is used in the construction of pile of plates.
(ii) It consists of a number of glass plates placed one over the other in a tube. The plates are inclined at an angle of `33.7^@ ( 90^@ - 56.3)` to the axis of the tube.
(iii) A beam of unpolarised light is allowed to fall on the pile of plates along the axis of the tube.
(iv). So, the angle of incidence of light will be at `56.3^@` which is the polarising angle for glass. The vibrations perpendicular to the plane of incidence are reflected at each surface and those parallel to it are transmitted.
(v) The larger the number of surfaces, the greater is the intensity of the reflected plane polarised light. The pile of plates is used as a polarizer and also as an analyser.