question_answer 61)

  A jar of height h is filled with a transparent liquid of refractive index |i, Fig. 6(EP).12. At the centre of the jar on the bottom surface is a dot Find the minimum diameter of a disc, such that when placed on the top surface symmetrically about the centre, the dot is invisible.

Answer:

                  In Fig. 6(EP).13, O is a dot on the bottom surface of a jar of height h, filled with a transparent liquid of refractive index  is diameter of a disc such that when placed on the top surface, symmetrically about the centre, the dot is invisible. This would happen when rays OA and OB suffer total internal reflection.                 If    then    ?(i)                 For total internal reflection,  ic,                 When                                    And         Fig .6(EP) .13.    ?(ii)                 From (i) and(ii),