A ray of light travelling inside a rectangular glass block of refractive index `sqrt(2)` is incident on the glass–air surface at an angle of incidence of `45^(@)`. The refractive index of air is 1. Under these conditions the ray

Options

A. be reflected back into glass
B. be absorbed
C. emerge into air with an angle of refraction equal to `90^(@)`
D. emerge into air without any deviation

Answer

C

Explanation

The ray is travelling from glass to air (from a denser medium to a rarer medium) .
`because i= 45^(@) therefore sini = sin 45^(@) = (1)/(sqrt2)`
But n `= (1)/(sin C) therefore sqrt2 = (1)/(sin C)`
`therefore sin C = (1)/(sqrt2) = sin 45^(@) therefore C = 45^(@)`
i.e., the ray is incident at the critical angle or i= C and when i= C , `r = 90^(@)` i.e. the ray will emerge in air with an angle of refraction equal to `90^(@)`.