The electromagnetic spectrum is divided into six broad bands. Electromagnetic radiation with the shortest and most energetic wavelengths, not larger than .01nm, is called gamma radiation. Gamma rays are often emitted in the course of nuclear reactions and by radioactive elements.



Electromagnetic radiation with wavelengths between .01nm and 20nm is referred to as X-rays, while radiation intermediate between X-rays and visible light is ultraviolet. Visible light ranges from 400-700nm. Infrared is approximately 103nm to 106nm. Infrared is also referred to as heat radiation. The microwaves used in shortwave communication and in television are radio waves with wavelengths ranging from a few centimeters to a few meters. Other radio radiation can have wavelengths as long as several kilometers. The array of radiation of all wavelengths is called the electromagnetic spectrum.

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