Why the brilliance of diamond is observed ?

Explanation

Diamonds are known for their spectacular brilliance. Their brilliance is mainly due to the total internal reflection of light inside them.
The critical angle for diamond-air interface `(cong 24.4^@)` is very small, therefore once light enters a diamond, it is very likely to undergo total internal reflection inside it.
`therefore` For total internal reflection,
`sini_c=1/n`
`therefore n = (1)/(sin 24.4^@)`
`therefore n =(1)/(0.4131)`
`therefore n = 2.42`
Thus, by phenomena of total internal reflection, refractive index of diamond can be found.