Which statement correctly describes circular polarization?

• A. The electric field vector rotates in time with a constant magnitude as the wave propagates.
• B. The electric field remains fixed in space and does not rotate.
• C. The electric field amplitude increases with time.
• D. The electric field is always parallel to the magnetic field.

Answer: (A)

Circular polarization means the electric field is always in the transverse plane and the tip of the E vector moves in a circle as time passes. This happens when the two perpendicular components of the electric field have equal amplitudes and a 90-degree phase difference. Because of that phase difference, the magnitude of the resultant E field stays constant while its direction rotates at the wave frequency, so the vector sweeps around in a circle as the wave propagates. In a plane wave, E and B remain perpendicular to the direction of travel, with E and B also perpendicular to each other, not parallel. The other descriptions describe linear polarization (fixed direction), a changing magnitude, or E being parallel to B, none of which match circular polarization.