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.