Question

Refractive index of diamond is $2.42$. What do we mean from this?

• A. Speed of light in diamond is raised by a factor $2.42$ relative to that in vacuum
• B. Speed of light in diamond is lower by a factor $2.42$ relative to that in vacuum
• C. Speed of light in air equals to speed of light in diamond
• D. None of the above

Answer 1

Answer: (B)

Speed of light in diamond is lower by a factor $2.42$ relative to that in vacuum

Given, refractive index of diamond

${\mu }_d=2.42$

We know, the refractive index of a medium is the ratio of speed of light in vacuum to the speed of light in that medium.

$\mu =\frac{c}{v}=\frac{Speedoflightinvacuum}{Speedoflightinmedium}$

$\Rightarrow v_d=\frac{c}{{\mu }_d}=\frac{c}{2.42}$

$\Rightarrow$ Speed of light in diamond is lower by a factor 2.42 relative to that in vacuum.

Hence, the correct answer is OPTION B.