The refracting angle of a prism is A and refractive index of the material of prism is `cot(A//2)` . The angle of minimum deviation will be

Options

A. 180 – A
B. 180 – 2A
C. 90 – A
D. A/2

Answer

B

Explanation

`mu=cos(A/2)/(sin(A/2))=sin((A+delta_m)/(2))/sin(A/2)`
`pi/2-A/2=A/2+(delta_m)/(2)`
`delta_m=180-2A`