Question

Choose the correct answer from the alternatives given.
A plane electromagnetic wave of frequency $25MHz$ travels in free space along $X$-direction. At a particular point in space and time, electric field $\overrightarrow{E}=6.3\hat{j}V/m$. What is $B$ at this point.

• A. $1.2\times {10}^{-6}T$
• B. $1.2\times {10}^{-8}T$
• C. $2.1\times {10}^{-6}T$
• D. $2.1\times {10}^{-8}T$

Answer 1

The correct option is D $2.1\times {10}^{-8}T$

Given: The frequency of the electromagnetic wave is $25MHz$.

The electric field at the particular point is $6.3\hat{j}V/m$

To find: The magnetic field at that point.

The magnetic field of the electromagnetic wave at a point is given by:

$B=\frac{E}{c}=\frac{6.3}{3\times {10}^8}\Rightarrow 2.1\times {10}^{-8}T$

So, option $\left(D\right)$ is correct.