Browse Questions

# If $c$ is the speed of electromagnetic waves in vacuum, their speed in a medium of dielectric constant $K$ and relative permeability $\mu_r$ is

$\begin {array} {1 1} (a)\;v =\large\frac{\mu}{\sqrt{\mu_r}} K & \quad (b)\;v =c \sqrt{\mu_r}\: K \\ (c)\;v =\large\frac{c}{\sqrt{\mu_r}}\: K & \quad (d)\;v =\large\frac{K}{\sqrt{\mu_r}} c \end {array}$

Speed of light in a medium $= \large\frac{1}{\sqrt{ \in \mu}}$
A dielectric medium reduces Coulomb’s constant, by the dielectric constant, thereby increasing $\in$
by the same amount and relative permeability increases $\mu$ by $\mu_r .$
Ans : (c)