Question

The index of refraction of diamond is $2.0$, velocity of light in diamond in $\text{cm/s}$ is approximately

• A. $6\times {10}^{10}$
• B. $3.0\times {10}^{10}$
• C. $2\times {10}^{10}$
• D. $1.5\times {10}^{10}$

Answer 1

The correct option is D $1.5\times {10}^{10}$

We know,

Refractive index of diamond is given by,

$=\frac{\text{Velocity of light in air}}{\text{Velocity of light in diamond}}$

$\Rightarrow 2=\frac{3\times {10}^8}{\text{velocity of light in diamond}}$

So, $\text{Velocity of light in diamond}=\frac{3\times {10}^8}{2}=1.5\times {10}^8\text{m/s}$

But we need velocity in $\text{cm/s}$

Therefore, velocity of light in diamond,

$1.5\times {10}^8\times {10}^2$

$1.5\times {10}^{10}\text{cm/s}$