Radio Wave
Introduction
Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. They have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers.
Discovery and Early Use
Radio waves were first predicted by mathematical work done in 1867 by Scottish mathematical physicist James Clerk Maxwell. His mathematical theory, now known as Maxwell's equations, predicted that coupled electric and magnetic fields could travel through space as an "electromagnetic wave". Radio waves were first observed and studied by German physicist Heinrich Hertz in 1886.
Properties
Like all other electromagnetic waves, radio waves travel at the speed of light in vacuum. They are generated by electric charges undergoing acceleration, such as time varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, or are induced by reflections from terrestrial objects.
Generation of Radio Waves
Radio waves are generated artificially by transmitters and received by radio receivers using antennas. Radio waves are very widely used in modern technology for fixed and mobile radio communication, broadcasting, radar and other navigation systems, communications satellites, wireless computer networks and many other applications.
Propagation of Radio Waves
Radio wave propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere. The study of radio propagation allows predictions to be made of the path that the radio waves will take, and thus the performance of the radio link.
Uses of Radio Waves
Radio waves are used for wireless transmission of sound messages, or information, using Morse code, or more advanced modulation techniques such as amplitude modulation (AM), frequency modulation (FM) and phase modulation (PM). They are also used for transmission of data in computer networks, and for broadcasting of television and radio programs.
Health and Safety
The interaction of radio waves with living tissue can be a health concern. The heating effect of radio waves forms the underlying basis of current safety guidelines. Acute exposure to high intensity radio waves can cause burns or cataracts, but these are usually the result of equipment malfunctions.