Question

If $c$ is the speed of electromagnetic waves in vacuum, its speed $v$ in a medium of dielectric constant $K$ and relative permeability $\mu_{r}$ is (c is the speed of light)

• A. $v=\frac{1}{\sqrt{\mu_{r} K}}$
• B. $v=c \sqrt{\mu_{r} K}$
• C. $v=\frac{c}{\sqrt{\mu_{r} K}}$
• D. $v=\frac{K}{\sqrt{\mu_{r} c}}$

Answer 1

Answer: (C)

Speed of light in vacuum, $c=\frac{1}{\sqrt{\mu_{0} \varepsilon_{0}}}$
and in another medium $v=\frac{1}{\sqrt{\mu \varepsilon}}$
$\therefore \frac{c}{v}=\sqrt{\frac{\mu \varepsilon}{\mu_{0} \varepsilon_{0}}}=\sqrt{\mu_{r} K}$
$\Rightarrow v=\frac{c}{\sqrt{\mu_{r} K}}$