A prism having an apex angle `4^(@)` and refractive index 1.5 is located in front of a vertical plane mirror as shown in figure. Through what total angle is the ray is deviated after reflection from the mirror ?

Options

A. `176^(@)`
B. `4^(@)`
C. `178^(@)`
D. `2^(@)`

Answer

C

Explanation

For this prism -
`delta_(P) = A (n - 1) = (1.5 - 1 ) 4^(@) rArr delta_(P) = 2^(@)`
total deviation
`delta_(T) = delta_(P) + delta_(mirror)`
`= 2^(@) + (180 - 2i) = 2^(@) + (180 - 2 xx 2) = 178^(@)`.