Question

A prism of refracting angle 4${}^o$ is made of a material of refractive index 1.652. Find its angle of minimum deviation.

Answer 1

Minimum deviation $\delta =2i-A$

where A is prism angle $A=4^o$

For minimum angle the angle of refraction should be half of prism angle.

So $r=A/2=2^o$

now using the snell's law

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

$1\times sini=1.652sin2$

$sini=1.652\times 0.035=0.058$

$i={3.3}^o$ , incidence angle

Minimum deviation $\delta =2i-A$

$\delta =2\times 3.3-4={2.6}^o$