Question

For a transparent medium, relative permeability, ${\mu }_r=1.0$ and relative permittivity, ${ϵ}_r=1.44$. The velocity of light in this medium will be -

• A. $2.5\times {10}^8\text{m/s}$
• B. $3.0\times {10}^8\text{m/s}$
• C. $2.8\times {10}^8\text{m/s}$
• D. $2.7\times {10}^8\text{m/s}$

Answer 1

The correct option is A $2.5\times {10}^8\text{m/s}$

We know that, refractive index,

$n=\frac{c}{v}=\sqrt{{\mu }_r{ϵ}_r}$

$\Rightarrow v=\frac{c}{\sqrt{{\mu }_r{ϵ}_r}}=\frac{3\times {10}^8}{\sqrt{1.0\times 1.44}}$

​​​​​​​$\Rightarrow v=2.5\times {10}^8\text{m/s}$

Hence, option $\left(A\right)$ is the correct answer.