Electromagnetic waves travel in a medium at a speed of 2 × 108 m/s. The relative permeability of medium is 1. Find relative permittivity.

1.5 1.8 2 2.25

2.25

$c^{\prime}=\frac{1}{\sqrt{\mu \varepsilon}}=\frac{1}{\sqrt{\mu_0 \mu_r \varepsilon_0 \varepsilon_r}}=\frac{c}{\sqrt{\mu_r \varepsilon_r}}$ $\varepsilon_r=\frac{c^2}{c^{\prime 2} \mu_r}=\left(\frac{3}{2}\right)^2=2.25$.