Question

Electromagnetic waves travel in a medium with speed of 1.5 × 10⁸ ms^–1 . The relative permeability of the medium is 2.0. The relative permittivity will be : 

(1) 5 

(2) 1 

(3) 4 

(4) 2

Answer 1

Correct option is : (4) 2

\(\begin{aligned} & \text { Speed of light in vaccum }=\frac{1}{\sqrt{\mu_0 \in_0}}=3 \times 10^8 \\ & \text { Speed of light in medium }=\frac{1}{\sqrt{\mu_0 \in_0} \cdot \sqrt{\mu_{\mathrm{r}} \in_{\mathrm{r}}}}=\frac{3}{2} \times 10^8 \end{aligned} \)

Also, given, \(\epsilon_{\mathrm{r}}=2\), therefore, \(\mu_{\mathrm{r}}=2\) .