If angle of incidence is twice the angle of refraction in a medium of refractive index `mu` , then angle of incidence is

Options

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

Answer

A

Explanation

According to Snell's law
Refractive index ` ,mu=(sin i)/(sin r)`
Given `i=2r`
` :. mu=(sin2r)/(sin r)`
or ` mu=(2 sin r cos r)/(sin r )`
or ` cos^(-1)""(mu)/(2)=r`
`implies i = 2 cos^(-1)""(mu)/(2)`