Question

A ray of light incident on a 60${}^o$ angled prism of refractive index $\sqrt{2}$ suffers minimum deviation. The angle of incidence is :

• A. 70${}^o$
• B. 0${}^o$
• C. 45${}^o$
• D. 60${}^o$

Answer 1

The correct option is C 45${}^o$

We know that in case of minimum deviation, the Angle of refraction is half of the prism angle.

So $r=\frac{A}{2}=\frac{60}{2}={30}^o$ , where A is prism angle.

Now using the Snell's law

$n_{air}sini=n_{glass}sin30$

$sini=\sqrt{2}\frac{1}{2}$

$i={45}^o$