Why do diamonds sparkle when white light is directed at them?

Last updated on April 14th, 2021 at 04:54 pm

Diamonds sparkle when white light is directed at them – the optical phenomenon behind this is Total internal reflection of light rays. Let’s discuss this in details.

Diamonds sparkle when white light is directed at them – why and how?

When white light enters a diamond, it is split into the colours of the spectrum. Diamond has a very high refractive index of 2.417 so it separates the colours more than any other substance does.

In addition, the high refractive index gives diamond a critical angle of 24.4°.
(As, Sin θ_c = 1/µ where θ_c is the critical angle and µ is the refractive index)

So a light ray in a diamond may be totally internally reflected many times before it emerges, which means its colours spread out more and more.

So the diamond sparkles with different colours.