A ray of light passes from vaccume into a medium of refractive index n. if the angle of incidence is twice the angle of refraction, then the angle of incidence is

Options

A. `cos^(-1) ((n)/(2))`
B. `sin^(-1) ((n)/(2))`
C. `2 cos^(-1) ((n)/(2))`
D. `sin^(-1)` n

Answer

C

Explanation

Since, `(sin i)/( sin r) = n rArr (sin 2r)/(sin r) = n `
`rArr " " (2 sin r cos r )/(sin r) = n rArr r = cos^(-1) ((n)/(2))`
`i = 2r = 2 cos^(-1) ((n)/(2))` .