Physics » Electromagnetic Waves » The Electromagnetic Spectrum



Microwaves are the highest-frequency electromagnetic waves that can be produced by currents in macroscopic circuits and devices. Microwave frequencies range from about \({\text{10}}^{9}\phantom{\rule{0.25em}{0ex}}\text{Hz}\) to the highest practical \(\text{LC}\) resonance at nearly \({\text{10}}^{\text{12}}\phantom{\rule{0.25em}{0ex}}\text{Hz}\). Since they have high frequencies, their wavelengths are short compared with those of other radio waves—hence the name “microwave.”

Microwaves can also be produced by atoms and molecules. They are, for example, a component of electromagnetic radiation generated by thermal agitation. The thermal motion of atoms and molecules in any object at a temperature above absolute zero causes them to emit and absorb radiation.

Since it is possible to carry more information per unit time on high frequencies, microwaves are quite suitable for communications. Most satellite-transmitted information is carried on microwaves, as are land-based long-distance transmissions. A clear line of sight between transmitter and receiver is needed because of the short wavelengths involved.

Radar is a common application of microwaves that was first developed in World War II. By detecting and timing microwave echoes, radar systems can determine the distance to objects as diverse as clouds and aircraft. A Doppler shift in the radar echo can be used to determine the speed of a car or the intensity of a rainstorm. Sophisticated radar systems are used to map the Earth and other planets, with a resolution limited by wavelength. (See this figure.) The shorter the wavelength of any probe, the smaller the detail it is possible to observe.

Continue With the Mobile App | Available on Google Play

[Attributions and Licenses]

This is a lesson from the tutorial, Electromagnetic Waves and you are encouraged to log in or register, so that you can track your progress.

Log In

Share Thoughts