Question

At what angle will a ray of light be inclined on one face of an equilateral prism, so that the emergen ray may graze the second surface of the prism $\left(\mu =2\right)$

• A. ${30}^0$
• B. ${90}^0$
• C. ${45}^0$
• D. ${60}^0$

Answer 1

The correct option is B ${90}^0$

REF.Image

According to the question

For the emergent ray

$\frac{sin{r}_2}{sin{90}^{\circ }}=\frac{1}{\mu }$

$sin{r}_2=\frac{1}{2}$

$r_2={30}^{\circ }$

Also, by the $e{q}^n$

$r_1+r_2=A={60}^{\circ }$

$r_1+{30}^{\circ }={60}^{\circ }\Rightarrow r_1={30}^{\circ }$

Then,

$\frac{sini}{sin{r}_1}=\mu \Rightarrow sini=\frac{2}{2}=1$

$i={90}^{\circ }$