Question

For plane electromagnetic waves propagating in the $z-$ direction, which one of the following combinations give the correct possible direction for $\overrightarrow{E}$ and $\overrightarrow{B}$ fields respectively?

• A. $(2\hat{i}+3\hat{j})\text{and}(\hat{i}+2\hat{j})$
• B. $(-2\hat{i}-3\hat{j})\text{and}(3\hat{i}-2\hat{j})$
• C. $(3\hat{i}+4\hat{j})\text{and}(4\hat{i}-3\hat{j})$
• D. $(\hat{i}+2\hat{j})\text{and}(2\hat{i}-\hat{j})$

Answer 1

The correct option is B $(-2\hat{i}-3\hat{j})\text{and}(3\hat{i}-2\hat{j})$

For an electromagnetic wave, $\overrightarrow{E}.\overrightarrow{B}=0$ $\because [\overrightarrow{E}\perp \overrightarrow{B}]$


$\overrightarrow{E}\times \overrightarrow{B}$ should be along $Z-$ direction.
$(-2\hat{j}-3\hat{j})\times (3\hat{i}-2\hat{j})=5\hat{k}$