H-polaroid is prepared by

Options

A. orienting herapathite crystal in the same direction in nitrocellulose
B. using thin tourmaline crystals
C. stretching polyvinyl alcohol and then heated with dehydrating agent
D. stretching polyvinyl alcohol and then impregnating with iodine.

Answer

D

Explanation

H-polaroid is obtained by stretching a thin sheet of polyvinyl alcohol strained with iodine. When such a sheet is subjected to large strain, the molecules get oriented in the direction of applied strain. Each polaroid sheet is enclosed between thin glass plates so as to provide mechanical support.