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8.Electromagnetic waves
medium
For plan electromagnetic waves propagating in the $z-$ direction, which one of the following combination gives the correct possible direction for $\vec E$ and $\vec B$ field respectively?
A
$\left( {2\hat i + 3\hat j} \right)$ and $\left( {\hat i + 2\hat j} \right)$
B
$\left( {-2\hat i - 3\hat j} \right)$ and $\left( {3\hat i - 2\hat j} \right)$
C
$\left( {3\hat i + 4\hat j} \right)$ and $\left( {4\hat i - 3\hat j} \right)$
D
$\left( {\hat i + 2\hat j} \right)$ and $\left( {2\hat i - \hat j} \right)$
(JEE MAIN-2015)
Solution
As we know, $\vec E \cdot \vec B = 0$ $\because [\vec E \bot \vec B]$ and $\vec{E} \times \vec{B}$ should be along $Z$ direction
As $(-2 \hat{i}-3 \hat{j}) \times(3 \hat{i}-2 \hat{j})=13 \hat{k}$
Hence option $(b)$ is the correct answer.
Standard 12
Physics
