A transparent cylinder has its right half polished so as to act as a mirror. A paraxial light ray inciden from left, that is parallel to the principal to the incident ray as shown. The refractive index n of the material of the cylinder is

Options

A. `1.2`
B. `1.5`
C. `1.8`
D. `2.0`

Answer

D

Explanation

For spherical surface
using `(n_(2))/(v)-(n_(1))/(u)=(n_(2)-n_(1))/(R)`
`rArr (n)/(2R)-(1)/(oo) = (n-1)/(R)`
`rArr n=2n-2 rArr n=2`.