Question

The speed of electromagnetic wave in a medium, having dielectric constant $2.25$ and relative permeability $4$, is equal to,

• A. $0.5\times {10}^8\frac{m}{s}$
• B. $0.25\times {10}^8\frac{m}{s}$
• C. $0.75\times {10}^8\frac{m}{s}$
• D. $1\times {10}^8\frac{m}{s}$

Answer 1

The correct option is D $1\times {10}^8\frac{m}{s}$

Given :-
Relative permeability, ${\mu }_r=4$
Dielectric constant, $K={ϵ}_r=2.25$

The speed of electromagnetic wave is given by,

$V=\frac{1}{\sqrt{\mu ϵ}}=\frac{1}{\sqrt{\left({\mu }_0{\mu }_r\right)\left({ϵ}_0{ϵ}_r\right)}}$

$V=\frac{1}{\sqrt{{\mu }_0{ϵ}_0}}\times \frac{1}{\sqrt{{\mu }_r{ϵ}_r}}$

$V=\frac{c}{\sqrt{{\mu }_r{ϵ}_r}}=\frac{3\times {10}^8}{\sqrt{2.25\times 4}}$

$\therefore V={10}^8\frac{m}{s}$

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