Radio wave

Radio waves are electromagnetic waves of wavelength between 10 cm and 100 kilometers can be up to about 3 GHz in a frequency range of a few kilohertz ( long waves ) - where to connect the radar and microwave range. Radio waves can be of natural or technological origin. They can not be detected (eg receiver) without technical aids, as they are outside of human perception range.

History

The existence of radio waves has been predicted from the theoretical considerations, by James Clerk Maxwell. 1887 were detected by Heinrich Hertz experimentally.

Technical radio waves

The technology used frequencies of the electromagnetic spectrum ranging over the long shafts up to terahertz radiation. Their technical use is governed by internationally agreed frequency bands.

Radio or radio waves are used for line-free transmission of voice, images or other data, such as time code, for broadcasting, for location / terrain scanning ( radar) and navigation (GPS, radio direction finding ) is used.

The information to be transmitted is in the message transmission of a carrier wave by the modulation impressed on and emitted from the transmitting antenna. In the receiving antenna is induced by radio waves similar vibrations, of which following prior amplification, the information is demodulated again. Only because of the possibility to transmit similar messages independently with transmitters with different carrier frequency, you can choose from the wide selection of simultaneously emitted radio and television programs. For the same reason, it is possible to transmit to the telephone on a wire several hundred calls simultaneously and without mutual interference. The selection of the desired carrier frequency is performed by the resonant circuits.

Radio waves are also used for heating (drying, curing, therapeutic purposes, microwave) used by utilizing the heat in their absorption.

Occurrence in nature

The radio waves from space devoted to radio astronomy. Is known, for example, the radiation of the free hydrogen in the Milky Way at a wavelength of 21 cm. Other examined by the radio astronomy frequencies come from giant stars, pulsars, of so-called active galaxies and quasars. Particularly important for the development of today's idea of ​​the universe was the discovery of quasars and the cosmic background radiation. The first was discovered in 1932 by Karl Guthe Jansky, the radio emission from the Milky Way. The disturbance German radars led to the discovery of a strong radio source in the constellation Cygnus. Meanwhile, it has been found millions of such sources, the radiation originates from matter low temperature or accelerated flows of electrically charged elementary particles. The sun and some planets also emit radio waves.

Lightning generates strong radio waves, which can be used for their detection ( atmospheric disturbances ).