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

• A

  $\mathrm{v}=\frac{1}{\sqrt{{\mathrm{\mu }}_{\mathrm{r}}\mathrm{K}}}$

• B

  $\mathrm{v}=\mathrm{c}\sqrt{{\mathrm{\mu }}_{\mathrm{r}}\mathrm{K}}$

• C

  $\mathrm{v}=\frac{\mathrm{c}}{\sqrt{{\mathrm{\mu }}_{\mathrm{r}}\mathrm{K}}}$

• D

  $\mathrm{v}=\frac{\mathrm{K}}{\sqrt{{\mathrm{\mu }}_{\mathrm{r}}\mathrm{c}}}$