Question

Critical angle is minimum for which colour of VIBGYOR?

Answer 1

Critical angle will be minimum for violet colour of the spectrum.

We know that refractive index μ is given as c/v where c is the velocity of light and v is the velocity of the respective colour in the medium.

In refraction , the velocity of the red colour is maximum and that of the violet colour is minimum.

Also we know that :

μ = 1/sin C where C is the critical angle.

Substituting μ= c/v , we get,

c/v = 1/sin C

hence v ∝ sin C

as a result C will be minimum for minimum v and that is violet colour