Radio is technology that uses electromagnetic radio waves to transmit and receive information. Radio waves can be used for one-way broadcasting or two-way communication.
Information, including sound, can be sent and received using radio waves. Radio waves are the part of the electromagnetic spectrum that have the longest wavelengths. They can carry information by modulating different properties of the waves, such as amplitude or frequency.
James Clerk Maxwell demonstrated that electromagnetic waves could move through space. Heinrich Hertz proved their existence in a series of experiments, which prompted research on how Hertzian waves could be used. The first radio telegraph system was developed by Guglielmo Marconi. In 1901, Marconi successfully managed to send a message across the Atlantic. This technology was later developed into a system of amplitude modulation, allowing for the transmission of sound.
Advances in signal amplification meant that radio sets were no longer just available to trained technicians. The general public could start to buy radio sets and have them in their homes. Radio became a mass medium for home entertainment in the 1920s. Radio communication became especially important during the Second World War, as it allowed for wireless communication between soldiers. People at home were kept updated by broadcasts that kept them aware of the war efforts abroad.
Radio systems require a transmitter that produces modulated radio waves and a receiver. Each of these parts needs to have an antenna, a speaker, and a microphone. Radio systems can be simplex, meaning only one end can transmit at any time, or duplex, where two frequencies are used and both ends can transmit and receive at the same time.
Radio waves have a number of uses. The most well known is one-way radio broadcasting. AM (amplitude modulation) and FM (frequency modulation) are two methods used to broadcast on radio frequencies. Radio broadcasting is used for entertainment and to share information. Two-way radio communication is used in a wide range of fields, such as aviation, marine, and first responders. Radio can also be used to control objects including model boats and planes.