Various types (frequencies) of radio waves are used for communications.
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Radio waves are a type of electromagnetic
radiation. A radio wave has a much
longer wavelength than
light. We use radio waves extensively for communications.
Radio waves have wavelengths as short as a few millimeters (tenths of inches)
and as long as hundreds of kilometers (hundreds of miles). Visible light, for
comparison, has wavelengths in the 400 to 700 nanometer range, about 5,000
times shorter than the shortest wavelength radio waves. Radio waves oscillate
at frequencies between a few kilohertz (kHz or thousands of hertz) and a few
terahertz (THz or 1012 hertz). "Far
infrared" radiation borders radio waves on the
electromagnetic spectrum; far IR is slightly higher energy and shorter wavelength
radiation than radio.
Microwaves, which we use for cooking and for communication, are short wavelength
radio waves with wavelengths between a few and a few hundred millimeters (tenths
of inches to tens of inches).
Various frequencies of radio waves are used for television and FM and AM radio
broadcasts, military communications, mobile phones, ham radio, wireless computer
networks, and numerous other communications applications.
Most radio waves pass freely through Earth's atmosphere. However, some frequencies
can be reflected or absorbed by the charged particles in the ionosphere.
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