Ultraviolet ray


noun, plural: ultraviolet rays

A ray characterized generally by a wavelength between 10 nm to about 400 nm


The electromagnetic spectrum pertains to the entire range of wavelengths of electromagnetic radiation. It includes gamma rays, X-rays, UV, visible light, infrared, microwaves, and radio waves. The ultraviolet (UV) rays have wavelengths ranging from about 10 nm to about 400 nm. They are that portion of the electromagnetic spectrum immediately below the visible range and extending into the X-ray frequencies. The longer wavelengths (near-UV or biotic or vital rays) are necessary for the endogenous synthesis of vitamin D and are also called antirachitic rays. The shorter, ionizing wavelengths (far-uv or abiotic or extravital rays) are viricidal, bactericidal, mutagenic, and carcinogenic and are used as disinfectants.

UV radiation have many subtypes: ultraviolet A, ultraviolet B, ultraviolet C, near ultraviolet, middle ultraviolet, far ultraviolet, hydrogen lyman-alpha, vacuum ultraviolet, and extreme ultraviolet. Ultraviolet A, for instance, is ultraviolet radiation from 315 to 400 nm. It causes skin tanning but is very weakly sunburn-producing and carcinogenic. Ultraviolet B is an ultraviolet radiation from 280 to 315 nm that most effectively causes sun burning and tanning. Therefore, excessive uVB exposure is capable of causing cancer of fair skin.

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