Question

A prism produces same deviation for two different incident angles, what is prism angle

Answer 1

A ray of light is deflected twice in a prism. The sum of these deflections is the deviation angle. When the entrance and exit angles are equal, the deviation angle of a ray passing through a prismwill be a minimum.

Answer 2

i1=i

i2=e

Angle of a prism =A

Angle of deviation =i+e-A

40°=42°+37°-A

A=79-40

A=39°