The figure shows the square face (of side 'a') of a transparent cuboidal block. The thickness or the third dimension of the block is negligible in comparison to 'a'. The block has uniform refrative index `mu` equal to `2`. A point source `S` which can emit light in all directions can move inside the block. It is desired that no light of `'S'` should pass through `AB`. Sketch the region in which `S` should be present to satisfy this condition.

Answer

`(##RES_OPT_PHY_XII_C01_E01_238_A01##)`

Explanation

`sin C=(1)/(2),C=30^(@)`
If `S` is anywhere in the shaded region, the light rays from `S` will strike `AB` making an angle more than critical angle.