Physics - Geometrical Optics Question with Solution | TestHub

Critical angle ${\theta }_C={\sin }^{-1}\left(\frac{1}{\sqrt{2}}\right)=45^{\circ }$ Snell's law at points, $\left(\because n_1\sin {\theta }_1=n_2\sin {\theta }_2\right)$ $1\sin 45^{\circ }=\sqrt{2}\sin \theta$ $\therefore \theta =30^{\circ }$ At $P\because$ incidence angle at $P=75^{\circ }>{\theta }_C$ $\therefore$ TIR at point $P$ At $Q\because$ incidence angle at $Q=15^{\circ }<{\theta }_C$ $\therefore$ Partial reflection and refraction at $Q.$ As $SP\Vert QR$, emergent ray at $R$ is parallel to incid, ray at $S$. $\therefore$ Net deviation $=180^{\circ }$