Question

Angle of a prism is A and its one surface is silvered. Light rays falling at an angle of incidence of 2A on first surface return back through the same path after suffering reflection at the second silvered surface. Refractive index of the matrial is:

• A. 2 sin A
• B. 2 cos A
• C. (1/2) cos A
• D. tan A

Answer 1

The correct option is B 2 cos A

(Refer The Image)
So,

This implies,

Using Snell's Law:



Therefore,