Light enters a triangular at an incident angle of $\theta$ at the point Q with an angle of refraction equal to $90^{\circ}$ , What is the refractive index of prism in terms of $\theta$ . The angle of the prism is $90^{\circ}$

Question

 

$(a)\;(1+\sin ^2 \theta) \\ (b)\;(\sin ^2 \theta-1)^{1/2} \\ (c)\;(1+\sin ^2 \theta)^{1/2} \\ (d)\;(\sin ^2 \theta-1)$