Microwaves are electromagnetic waves that have lower frequencies (and longer wavelengths) than infrared light. They are higher on the frequency scale of the electromagnetic spectrum than radio waves. Their wavelengths range between 1 mm and 30 cm. The existence of microwaves was predicted by James Clerk Maxwell from his electromagnetic wave equations but only experimentally verified by Heinrich Hertz. While we do not usually think of microwaves as a form of light, they follow the same laws and possess the same properties as other forms of electromagnetic radiation, including visible light. Microwaves can show refraction, reflection, and diffraction patterns just as visible light does.
Microwaves are seen all over the universe-literally. The cosmic background radiation, which seems to be roughly isotropic, or the same in every direction, is composed of microwaves left over from the energy of the big bang. These microwaves have interacted with matter very little, if at all, since the Big Bang. Their existence must be explained in any theory that purports to explain the origins and age of the universe.
Microwave technology is widely used in radar detection systems. Microwave pulses are bounced off distant objects, and from the time it takes the reflected pulse to return, radar experts can determine the distance of the object. The interference pattern provided also gives a rough estimate of the shape of the object. Microwaves are also used for communications. Because of their shorter wavelength, they have a higher bandwidth than radio waves. They are used to transmit many different types of data including phone, cable television and internet traffic. It is often possible to spot microwave dish antennas at the tops of towers or tall buildings.
Some researchers hope microwaves could be used as a future energy source. They would plan to put a solar energy collector out in space, where the atmosphere would have less of an attenuating effect on the light intensity. The collector would then convert the collected energy into microwave energy and beam the microwaves down to power reception stations on Earth.
While most people use microwaves in their daily lives, their existence is usually taken for granted. They are commonly used to heat food in microwave ovens, taking advantage of the fact that water molecules excite easily in the microwave range. Since most foods have high water content, microwaves in microwave ovens take advantage of the water to heat the foods thoroughly. In addition, radiation at those wavelengths kills many types of bacteria that might otherwise be damaging to human beings. Microwave technology has thus become a widely used facet of electromagnetics.
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