Question

A plane electromagnetic wave travels in free space along the x-direction. The electric field component of the wave at a particular point of space and time is $E=6V{m}^{-1}$ along y-direction. Its corresponding magnetic field component, $B$ would be

• A. $6\times {10}^{-8}T$ along z-direction
• B. $6\times {10}^{-8}T$ along x-direction
• C. $2\times {10}^{-8}T$ along z-direction
• D. $2\times {10}^{-8}T$ along y-direction

Answer 1

The correct option is C $2\times {10}^{-8}T$ along z-direction

The direction of propogation of an $EM$ wave is parallel to the direction of $\overrightarrow{E}\times \overrightarrow{B}$.
$\hat{i}=\hat{j}\times \hat{B}$
$⟹\hat{B}=\hat{k}$
$c=\frac{E}{B}\Rightarrow B=\frac{E}{c}=\frac{6}{3\times {10}^8}$
$B=2\times {10}^{-8}T$ along z-direction.