Question:
Electric field of plane electromagnetic wave propagating through a non-magnetic medium is given by $E=20 \cos \left(2 \times 10^{10} \mathrm{t}-200 \mathrm{x}\right) \mathrm{V} / \mathrm{m}$. The dielectric constant of the medium is equal to :
$\left(\right.$ Take $\mu_{\mathrm{r}}=1$ )
Correct Option: 1
Solution:
Speed of wave $=\frac{2 \times 10^{10}}{200}=10^{8} \mathrm{~m} / \mathrm{s}$
Refractive index $=\frac{3 \times 10^{8}}{10^{8}}=3$
Now refractive index $=\sqrt{\varepsilon_{\mathrm{r}} \mu_{\mathrm{r}}}$
$3=\sqrt{\varepsilon_{\mathrm{r}}(1)}$
$\Rightarrow \varepsilon_{\mathrm{r}}=9$
Click here to get exam-ready with eSaral
For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.