Dispersion
The velocity of light in a material, and hence its
index
of refraction, depends on the wavelength of the light. In general,
n varies inversely with wavelength: it is greater for shorter
wavelengths. This
causes light inside materials to be refracted by different amounts
according to the wavelength (or colour).
This gives rise to the colours seen through a prism. Rainbows are
caused by a combination of dispersion inside the raindrop and total
internal reflection of light from the back of raindrops. The
following is a chart giving the index of refraction for various
wavelengths of light in glass.
Variations of Index of Refraction in Glass
| Colour |
Wavelength |
Index of Refraction |
| blue |
434 nm |
1.528 |
| yellow |
550 nm |
1.517 |
| red |
700 nm |
1.510 |
Note:
In general shorter wavelengths (i.e. light towards the
blue end of the spectrum) have higher indices of refraction and get
bent more than light with longer wavelengths (towards the red end).