A certain prism is found to produce a minimum of`38^(@)`.It produces a deviation of `44^(@)`when the angle of incident is either`42^(@)`or`62^(@)` .What is the angle of incidence when it is undergoing minimum deviation?

Options

A. `45^(@)`
B. `49^(@)`
C. `40^(@)`
D. `55^(@)`

Answer

B

Explanation

`delta_("min")= 38^(@), delta = 44^(@), i =42^(@)`
`implies e = 62^(@)`
`delta` = i + e -A, 44 = 42+62-A
`implies A = 60^(@)`
`therefore delta_("min") = 2i-A , 38 = 2i-60`
`implies i = 49^(@)`