What is the relationship between electric and magnetic fields in radio waves?

What is the relationship between electric and magnetic fields in radio waves?

• A. They exist independently
• B. They cancel each other out
• C. They support each other and propagate through space at the speed of light
• D. They only propagate in a vacuum

Answer: (C)

Electric and magnetic fields in radio waves are interdependent parts of a single electromagnetic wave. As the wave moves, a changing electric field generates a magnetic field, and a changing magnetic field sustains the electric field in turn. They are perpendicular to each other and to the direction of propagation, and they vary in step so their peaks align. They carry energy together, described by the Poynting vector E × B, pointing along the direction of travel. The wave travels at the speed of light in the medium (in air that speed is essentially c; in other materials it's c divided by the refractive index). Thus radio waves are not two separate fields but a coupled pair that propagate through space at light speed.

Electric and magnetic fields in radio waves are interdependent parts of a single electromagnetic wave. As the wave moves, a changing electric field generates a magnetic field, and a changing magnetic field sustains the electric field in turn. They are perpendicular to each other and to the direction of propagation, and they vary in step so their peaks align. They carry energy together, described by the Poynting vector E × B, pointing along the direction of travel. The wave travels at the speed of light in the medium (in air that speed is essentially c; in other materials it's c divided by the refractive index). Thus radio waves are not two separate fields but a coupled pair that propagate through space at light speed.