Question

Find the angle of minimum deviation for an equilateral prism made of a material of refractive index 1.732. What is the angle of incidence for this deviation ?

Answer 1

=> i = 60°. So, the angle of incidence must be 60°.

Answer 2

Given :

refractive index =1.732

A= 60 °

n= sin (A+Dm/2)/ sin A/2

1.732= sin ( 60 +D/2)/ sin 30

1.732 x 1/2 = sin( 30 +Dm/2)

sin⁻¹(0.866)= 30 + Dm/2

60 =30+Dm/2

30 = Dm/2

Dm= 60 ⁰

Now dm=i+ i'- A

60=i+i'-60

i=i'

i= 60⁰

so angle of incidence must be 60⁰