Physics - EM Waves Question with Solution | TestHub

The speed of any electromagnetic wave (EM) like light in any medium of permeability, $\mu$ and permittivity, $\epsilon$ is given by $$\mathrm{v}=\frac{1}{\sqrt{\mu \epsilon }}$$ Also, $\mu ={\mu }_0{\mu }_r$ and $\epsilon ={\epsilon }_0{\epsilon }_r$ where, ${\mu }_0$ and ${\epsilon }_0$ are permeability and permittivity in free space and ${\mu }_{\mathrm{r}}$ and ${\epsilon }_{\mathrm{r}}$ are relative permeability and relative permittivity of medium respectively. Here, ${\mu }_{\mathrm{r}}=1.0$ $${\epsilon }_{\mathrm{r}}=1.44$$ $$\begin{array}{rl}\therefore \mathrm{v}& =\frac{1}{\sqrt{{\mu }_{\mathrm{r}}{\epsilon }_{\mathrm{r}}{\mu }_0{\epsilon }_0}}=\frac{\mathrm{c}}{\sqrt{{\mu }_{\mathrm{r}}{\epsilon }_{\mathrm{r}}}}\left[\because \mathrm{c}=\frac{1}{\sqrt{{\mu }_0{\epsilon }_0}}\right]\\ & =\frac{3\times 10^8}{\sqrt{1\times 1.44}}\\ & =2.5\times 10^8{\mathrm{ms}}^{-1}\end{array}$$