A ray of light falls on a transparent glass slab with refractive index (relative to air) of $1.62$ . The angle of incident for which the reflected and refractive rays are mutually perpendicular is :

Question

$(a)\;\tan ^{-1} (1.62) \\ (b)\;\sin ^{-1} (1.62) \\ (c)\;\cos^{-1} (1.62) \\ (d)\;None\;of \;these $