• # question_answer Two mirrors, placed perpendicularly, form two sides of a vessel filled with water. A light ray is incident on the water surface at an angle $\alpha$ and emerges at an angle $\beta$ after getting reflected from both the mirrors inside. The relation between $\alpha$ and $\beta$ is expressed as A)  $\alpha =\beta$                    B)  $\alpha >\beta$ C)  $\alpha <\beta$                    D)  All are possible, depending upon $\alpha$

By analysis the diagram and with the help of laws of reflection and refraction. $\alpha +90-{{\theta }_{1}}+90-\theta$ $=90-\alpha +90+{{\theta }_{2}}+\theta ={{180}^{o}}$ $\Rightarrow$            $\alpha -{{\theta }_{1}}-\theta -\alpha +{{\theta }_{2}}+\theta =0$ and      $\alpha ={{\theta }_{2}}+\theta$ $\Rightarrow$            ${{\theta }_{1}}={{\theta }_{2}}$ $\Rightarrow$            $\alpha =\beta$