# White light is incident on the surface of glass and air as shown. Green light just grazes the surface. then the emergent ray in air contains

(a)yellow,orange, red

(b)violet, indigo,blue

(c)all colours

(d)all except green

Since green light grazes the surface after refraction the incident angle must be critical angle for green light.
As wavelength increases from violet to Red, the refractive index $\mu$ decreases from Violet, to Red.
and Since $\theta_c=\sin ^{-1} \large\frac{1}{\mu}$ we have critical angle increases from Violet to Red.
Critical angle for yellow orange and red and greater than $\theta_g$ .
Therefore they will emerge out in air, the other colours will be totally internally reflected.
Hence a is the correct answer.

edited Jan 20, 2014 by meena.p