11.In Nicol prism, the refractive indices for the ordinary ray and the extraordinary ray are

12.In a doubly refracting crystal, along the optic axis, the ordinary ray and the extraordinary ray

13.In Nicol prism, the phenomenon that takes place at the layer of Canada balsam is

14.The production of stereoscopic motion picture uses the principle of

15.A device using micro crystal of herapathite (iodosulphate of quinine) is used for the production of