The figure shows the path of a light ray through a triangular prism. In this phenomenon, the angle $\theta$ is given by : (A) $\sin^{-1} \sqrt{n^2 - 1}$ (B) $\sin^{-1} (n^2 - 1)$ (C) $\sin^{-1} \left[ \frac{1}{\sqrt{n^2 - 1}} \right]$ (D) $\sin^{-1} \left[ \frac{1}{(n^2 - 1)} \right]$