A ray of light falls on the surface of a spherical glass paper weight making an angle `alpha` with the normal and is refracted in the medium at an angle `beta`. The angle of deviation of the emergent ray from the direction of the incident ray is :

Options

A. `(alpha - beta)`
B. `2(alpha - beta)`
C. `(alpha - beta)//2`
D. `(beta - alpha)`

Answer

B

Explanation

In Fig. `AB` is incident ray suffering two refractions in the spherical glass paper weight and emerging out along `CD`. The angle of deviation (from `Delta EBC`).

`delta = /_EBC + /_ECB`
`= (alpha - beta) + (alpha - beta) = 2 (alpha - beta)`