A beam of monochromatic light is incident at `i= 50^(@)` on one face of an equilateral prism, the angle of emergence is `40^(@)`, then the angle of minimum deviation is :

Options

A. `30^(@)`
B. `lt30^(@)`
C. `le30^(@)`
D. `ge30^(@)`

Answer

B

Explanation

`I = 50^(@)` , equilateral prism `A = 60^(@) , e= 40^(@)`
Total angle of deviation
`delta =i+e - A = 50 + 40 - 60, delta= 30^(@)`
Hence `delta_("min") lt delta implies delta_("min") lt 30^(@)`