Chapter 32, Problem 32.1DQ

By measuring the electric and magnetic fields at a point in space where there is an electromagnetic wave, can you determine the direction from which the wave came? Explain.

To determine

The direction of electromagnetic wave by measuring electric and magnetic fields.

Explanation of Solution

The propagation direction of electromagnetic wave is perpendicular to vectors of electric filed and magnetic field.

Assume direction of electric filed and magnetic field can be found at a point in a space. The direction of propagation wave can be found by taking cross product of electric filed and magnetic field $\left(\overrightarrow{E}\times \overrightarrow{B}\right)$

From figure 1, electromagnetic wave direction is perpendicular to the vectors of electric filed and the magnetic field. Therefore, direction of electromagnetic wave is opposite to direction of $\left(\overrightarrow{E}\times \overrightarrow{B}\right)$.

Conclusion:

Therefore, direction of electromagnetic wave is opposite to direction of $\left(\overrightarrow{E}\times \overrightarrow{B}\right)$.