microwave

microwave, electromagnetic wave having a frequency range from 1,000 megahertz (MHz) to 300,000 MHz, corresponding to a wavelength range from 300 mm (about 12 in.) to 1 mm (about 0.04 in.). Like light waves, microwaves travel essentially in straight lines. They are used in radar, in communications links spanning moderate distances, and in other applications, such as microwave ovens. The equipment used to generate, process, and transmit microwaves is in many respects different from that used with lower frequency radio waves. See waveguide; magnetron.

---

microwave

Portion of the electromagnetic spectrum that is situated between radio waves and infrared radiation. Microwaves have wavelengths ranging from 30 cm to 1 mm, corresponding to frequencies from about 1 gigahertz (10⁹ Hz) to 1 terahertz (10¹² Hz). They are the principal carriers of television, telephone, and data transmissions between stations on Earth and between the Earth and satellites. Radar beams are short pulses of microwaves used to locate ships and planes, track weather systems, and determine the speeds of moving objects. Microwaves are absorbed by water and fat in foodstuffs and produce heat from the inside (see microwave oven). Materials such as glass and ceramics do not absorb microwaves, and metals reflect them. See also maser.

---

A radio signal in the frequency range of 1 GHz and above. Numerous transmission systems use microwaves including line-of-sight between buildings and across vast distances, communications satellites, PCS cellular systems and wireless LANs. See wireless local loop and spectrum.

Early Microwave Tower

Microwaves were first used to transmit across long distances that were difficult to wire as long as line-of-sight was possible. This tower was installed in 1969 in Boulder Junction, Colorado. (Image courtesy of AT&T.)