Question

A ray of light incident at an angle $\theta$ on a refracting face of a prism emerges from the other face normally. If the angle of the prism is $5^{\circ }$ and the prism is made of a material of refractive index 1.5. The angle of incidence is

• A. ${7.5}^{\circ }$
• B. $5^{\circ }$
• C. ${15}^{\circ }$
• D. ${2.5}^{\circ }$

Answer 1

The correct option is A ${7.5}^{\circ }$


$i_2=r_2=0^{\circ }$

$r_1+r_2=A$

$\Rightarrow r_1=A=5^{\circ }$

Snell's law at 1st refracting surface,

$\mu =\frac{sin{i}_1}{sin{r}_1}$

for small angled Prism, $\mu =\frac{i_1}{r_1}$
(or) $i_1=\mu r_1=1.5\times 5^{\circ }$

$={7.5}^{\circ }$