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. ` lt 30 ^@ `
C. ` le 30 ^@ `
D. ` ge 30 ^@ `

Answer

B

Explanation

Graph between ` ( delta -i) ` for prism
For the given condition
` delta = ( i+e-A) = 40 + 50 - 60 , delta = 30 `
Then ` delta _ (min ) lt delta , delta _ (min) lt 30 `