Question

In an electromagnetic wave the electric field vector and magnetic field vector are given as $\overrightarrow{E}=E_0\hat{i}$ and $\overrightarrow{B}=B_0\hat{k}$ respectively. The direction of propagation of electromagnetic wave is along :

• A. $(-\hat{j})$
• B. $\left(\hat{k}\right)$
• C. $(-\hat{k})$
• D. $\hat{j}$

Answer 1

The correct option is A $(-\hat{j})$

Given:
$\overrightarrow{E}=E_0\hat{i};\overrightarrow{B}=B_0\hat{k}$

As we know that, the direction of propagation of an electromagnetic wave is given by Poynting vector $\overrightarrow{S}$.

$\overrightarrow{S}=\frac{\overrightarrow{E}\times \overrightarrow{B}}{{\mu }_0}$

$\therefore$ Direction of propagation is,

$\overrightarrow{S}=\frac{E_0\hat{i}\times B_0\hat{k}}{{\mu }_0}=\frac{E_0{B}_0}{{\mu }_0}(-\hat{j})$

Hence, option $\left(\text{D}\right)$ is correct.