Question

Refractive idex of red colour and violet colour

Answer 1

Refractive index is a constant which is obtained from snell's law.

Snell's law states that for a definite colour of light and for a oblique incidence of light ray, when that ray travels from one medium to other medium at that time, the ratio of the sine of the angle of incidence to the angle of refraction is a constant.

That is,

$\frac{sin \: i}{sin \: r} = constant$

This constant is called the refractive index of the second medium with respect to the first medium.

Now, different colours have different speeds in several mediums (EXCEPT VACUUM OR AIR) and as a result different refractive indices.

While passing through a prism, a white light breaks into its constituent colours and a band of seven colours which is abbreviated as VIBGYOR (from bottom to top) is obtained on a white screen.

In this above case, Red light travels with highest velocity and thus it bends least with a small angular deviation whereas Violet light travels with least velocity and thus it bends highest with a big angular deviation.

As a result, we can say that, Red light suffers least deviation whereas Violet light suffers highest deviation, that is, it is deviated most.

Now refractive index is inversely proportional to speed of light in a medium and thus you can say when speed is highest, refractive index is least and conversely, when speed is least, refractive index is highest.