Question

Refractive index of an equilateral prism is `sqrt(2)`.
A. minimum deviation from this prism can be `30^(@)`
B. minimum deviation from this prism can be `45^(@)`
C. at angle of incidence `45^(@)` , deviation is minimum
D. at angle of incidence `60^(@)` , deviation is minimum

Answer 1

Correct Answer - A::C
From `mu=(sin((A+delta_(m))/(2)))/("sin"(A)/(2))`
We can see that `delta_(m)=30^(@)` for `(mu=sqrt(2)` and `A=60^(@))`
Further, at minimum deviation
`r_(1)=r_(2)-(A)/(2)=30^(@)`
`sini_(1)=musinr_(1)=(sqrt(2))sin30^(@)=(1)/(sqrt(2))`
`rArri_(1)=45^(@)`