Question

A plane e.m. wave of frequency 30 MHz 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 magnetic field component B at this point would be

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

Answer 1

The correct option is A

$2\times {10}^{-8}T$ along z - direction

$B=\frac{E}{c}=\frac{6}{3\times {10}^8}=2\times {10}^{-8}T$, along z - direction.

The direction of travel of e.m. wave is in the direction of vector $\overrightarrow{E}\times \overrightarrow{B}$.