Question

An electromagnetic wave in vacuum has the electric and magnetic field $\overrightarrow{E}$ and $\overrightarrow{B}$, which are always perpendicular to each other. If the direction of polarization is given by $\overrightarrow{X}$ and that of wave propagation by $\overrightarrow{k}$. then:

• A. $\overrightarrow{X}\parallel \overrightarrow{B}$ and $\overrightarrow{k}\parallel \overrightarrow{B}\times \overrightarrow{E}$
• B. $\overrightarrow{X}\parallel \overrightarrow{E}$ and $\overrightarrow{k}||\overrightarrow{E}\times \overrightarrow{B}$
• C. $\overrightarrow{X}\parallel \overrightarrow{B}$ and $\overrightarrow{k}\parallel \overrightarrow{E}\times \overrightarrow{B}$
• D. $\overrightarrow{X}\parallel \overrightarrow{E}$ and $\overrightarrow{k}||\overrightarrow{B}\times \overrightarrow{E}$

Answer 1

Answer: (B)

$\overrightarrow{X}\parallel \overrightarrow{E}$ and $\overrightarrow{k}||\overrightarrow{E}\times \overrightarrow{B}$

Direction of polarization is parallel to magnetic field,
$\therefore \overrightarrow{X}||\overrightarrow{E}$
And direction of wave propagation is parallel to $\overrightarrow{E}\times \overrightarrow{B}$
$\overrightarrow{k}||\overrightarrow{E}\times \overrightarrow{B}$