A ray of light strikes a plane mirror at an angle of incidence `45^@` as shown in Figure . After reflection,l the ray passes through a prism of refractive indes 1.5 whos apex angle is `4^@`. Through what angle must the mirror be rotated it total deviation of the ray be `90^@` ?

Options

A. `1^(@)` clockwise
B. `1^(@)` anticlockwise
C. `2^(@)` clockwise
D. `2^(@)` anticlockwise

Answer

B

Explanation

`rho=A(H-1)=4xx1/2=2^(@)`
:. total deviation `=90^(@)`(due to reflection)+`2^(@)` (due to prism)=`92^(@)`
but net deviation should be `90^(@)`
:. due to reflection `=88^(@)=pi-2iRightarrow i=46^(@)`
i.e. mirror mut lurotated by `1^(@)` anticlockwise.