04/02/2021
Ultraviolet light is a type of electromagnetic radiation that makes black-light posters glow, and is responsible for summer tans — and sunburns. However, too much exposure to UV radiation is damaging to living tissue.
Electromagnetic radiation comes from the sun and transmitted in waves or particles at different wavelengths and frequencies. This broad range of wavelengths is known as the electromagnetic (EM) spectrum. The spectrum is generally divided into seven regions in order of decreasing wavelength and increasing energy and frequency. The common designations are radio waves,microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays and gamma-rays.
Ultraviolet (UV) light falls in the range of the EM spectrum between visible light and X-rays. It has frequencies of about 8 × 1014 to 3 × 1016 cycles per second, or hertz (Hz), and wavelengths of about 380 nanometers (1.5 × 10−5 inches) to about 10 nm (4 × 10−7 inches). According to the U.S. Navy's "Ultraviolet Radiation Guide," UV is generally divided into three sub-bands:
UVA, or near UV (315–400 nm)
UVB, or middle UV (280–315 nm)
UVC, or far UV (180–280 nm)
