Question

The electric and the magnetic field, associated with an EM wave propagating along the $+z$ -axis, can be represented by

• A. $\left[\overrightarrow{E}=E{}_0\hat{i},\overrightarrow{B}=B{}_0\hat{j}\right]$
• B. $\left[\overrightarrow{E}=E{}_0\hat{k},\overrightarrow{B}=B{}_0\hat{i}\right]$
• C. $\left[\overrightarrow{E}=E{}_0\hat{j},\overrightarrow{B}=B{}_0\hat{i}\right]$
• D. $\left[\overrightarrow{E}=E{}_0\hat{j},\overrightarrow{B}=B{}_0\hat{k}\right]$

Answer 1

Answer: (A)

The electromagnetic wave is propagating along the +z axis.
Since the electric and magnetic fields are perpendicular to each other and also perpendicular to the direction of propagation of wave.
$\text{Also,}\overrightarrow{E}\times \overrightarrow{B}$ gives the direction of wave propagation.
$\overrightarrow{E}=E{}_0\hat{i}\text{,}B=B{}_0\hat{j}\left(\because \hat{i}\times \hat{j}=\hat{k}\right)$