Radio waves



Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths ranging from 1 millimeter to 100 kilometers. Like all other electromagnetic waves, they travel at the speed of light.

Naturally occurring radio waves are made by lightning, or by astronomical objects.

Artificially generated radio waves are used in innumerable applications. Radio waves are generated by transmitters and received by receivers. Different frequencies of radio waves have different propagation characteristics in atmosphere; long waves can diffract around obstacles like mountains and follow the ground's contour (ground waves), shorter waves can reflect off an ionosphere and return to the surface beyond the horizon (skywaves), while much shorter wavelengths bend or diffract very little and travel on a line of sight, so their propagation distances are limited to the visual horizon. This technology generally appears at the TL D level.