Question

The refractive index of diamond is 2.42 what is the meaning of this statement in relation to the speed of light.

Answer 1

We know that,
Refractive index = $\frac{Speedoflightinvacuum}{Speedoflightinthemedium}$

In the question refractive index of the diamond is 2.42

So we can write

$2.42=\frac{Speedoflightinvacuum}{Speedoflightindiamond}$

Or from the above equation, we can say that speed of the light in diamond in $\frac{1}{2.42}$ times the speed of light in vacuum.