# Amateur Extra: Circular Polarization

## What is meant by circularly polarized electromagnetic waves?

A. Waves with an electric field bent into a circular shape
B. Waves with a rotating electric field
C. Waves that circle the Earth
D. Waves produced by a loop antenna

To answer this we need to understand what’s going on inside an electromagnetic (or EM) wave.  In an EM wave, there is an electric field component, and a magnetic field component.  As it travels through space, the electric field and magnetic field exist at 90° angles to each other.  For example, in a vertically polarized wave, the electric field is straight up and down, or vertical and the magnetic field horizontal.

In a circularly polarized wave, the orientation of the electric and magnetic field rotates through space.  Every 1/4 wavelength, the orientation of the electric and magnetic fields change.  They remain at right angles to each other however.

Consider the above image.  This is what the electric field component of a circularly polarized wave looks like.

The answer then, is B. Waves with a rotating electric field.

[E3A17]