Calculating B-Field Strength in an Electromagnetic Wave

What is the maximum strength of the $B$ -field in an electromagnetic wave that has a maximum $E$ -field strength of $1000 V/m$ ?

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Strategy
To find the $B$ -field strength, we rearrange the above equation to solve for $B$ , yielding

$B = \frac{E}{c} .$
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Solution
We are given $E$ , and $c$ is the speed of light. Entering these into the expression for $B$ yields

$B = \frac{1000 V/m}{3.00 \times 10^{8} m/s} = 3 . 33 \times 10^{- 6} T,$
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Where T stands for Tesla, a measure of magnetic field strength.
Discussion
The $B$ -field strength is less than a tenth of the Earth’s admittedly weak magnetic field. This means that a relatively strong electric field of 1000 V/m is accompanied by a relatively weak magnetic field. Note that as this wave spreads out, say with distance from an antenna, its field strengths become progressively weaker.

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