Prove that i = e, If the angle of incidence and angle of emergence subtended by a light ray falling on a surface of glass slab are i and e respectively. How much angular deviation is suffered by the incident ray.

Explanation

In the following figure, `SR || PQ` and NM is the refracted ray. Hence, `r = i_(1)`.
Now, `._(g)n_(a) = sin i//sin r ` and `._(a) n_(g) = sin i_(1)//sin e `

Also `._(g)n_(a) = ( 1)/(._(a)n_(g))`
`:. ( sin i)/(sinr ) = ( sin e )/(sin i_(1))`
As ` r = i_(1)` , it follows that `sin i = sin e `
`:. i = e `