For a prism, `A=60^(@), n=sqrt(7//3)` . Find the minimum possible angle of incidence, so that the light ray is refracted from the second surface. Also, find `delta_(max)`.

Options

A. ` 30^@ `
B. ` 45 ^@ `
C. ` 60 ^ @ `
D. ` 90^@ `

Answer

A

Explanation

In minimum incidence case the angles will be as shown in figure.

Applying snell's law :
` 1xx sin i_(min) = sqrt((7)/(3))sin (A- C) `
` sqrt((7)/(3)) (sin A cos C - cos A sin C) `
` = sqrt ((7) /(3 )) (sin 60 sqrt( 1 - ( 3 ) /( 7)) - cos 60 sqrt((3)/(7)) ) = ( 1 ) /( 2 ) `
` therefore i_(min ) = 30 ^@ `