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ShareUltraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays.
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The Sun emits ultraviolet radiation in the UVA, UVB, and UVC bands, but because of absorption in the atmosphere's ozone layer, 99% of the ultraviolet radiation that reaches the Earth's surface is UVA.
(Some of the UVC light is responsible for the generation of the ozone.) Ordinary glass is partially transparent to UVA but is opaque to shorter wavelengths.
Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm.
In humans, prolonged exposure to solar UV radiation may result in acute and chronic health effects on the skin, eye, and immune system.
UVA, UVB and UVC can all damage collagen fibers and thereby accelerate aging of the skin.
In general, UVA is the least harmful, but can contribute to the aging of skin, DNA damage and possibly skin cancer.
It penetrates deeply and does not cause sunburn.
Because it does not cause reddening of the skin it cannot be measured in the SPF testing.
There is no good clinical measurement of the blocking of UVA radiation, but it is important that sunscreen block both UVA and UVB.
UVB light can cause skin cancer.
A positive effect of UVB light is that it induces the production of vitamin D in the skin.
For more information about the topic Ultraviolet, read the full article at Wikipedia.org, or see the following related articles:
Electromagnetic spectrum — The electromagnetic spectrum is the range of all possible electromagnetic radiation. Above infrared in frequency comes visible light. This is the ... > read more
Electromagnetic radiation — Electromagnetic radiation is a propagating wave in space with electric and magnetic components. These components oscillate at right angles to each ... > read more
Infrared — Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of microwave radiation. ... > read more
Spectroscopy — Spectroscopy is the study of spectra, that is, the dependence of physical quantities on frequency. Spectroscopy is often used in physical and ... > read more
Gamma ray — Gamma rays are an energetic form of electromagnetic radiation produced by radioactive decay or other nuclear or subatomic processes such as ... > read more
Photoelectric effect — The photoelectric effect is the emission of electrons from matter upon the absorption of electromagnetic radiation, such as ultraviolet radiation or ... > read more
Solar radiation — Solar radiation is radiant energy emitted by the sun, particularly electromagnetic energy. About half of the radiation is in the visible short-wave ... > read more
Editor's Note: This article is not intended to provide medical advice, diagnosis or treatment.
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