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In frequency (and thus energy), UV rays sit between the violet end of the visible spectrum and the X-ray range. The UV wavelength spectrum ranges from 399 nm to 10 nm and is divided into 3 sections: UVA, UVB, and UVC. UV is the lowest energy range energetic enough to ionize atoms, separating electrons from them, and thus causing chemical reactions.
There has also been a growing interest in ultraviolet communication (UVC) as a result of recent progress in solid-state optical sources/detectors operating within solar-blind UV spectrum (200–280 nm). In this so-called deep UV band, solar radiation is negligible at the ground level and this makes possible the design of photon-counting ...
The WHO-standard ultraviolet index is a widely publicized measurement of total strength of UV wavelengths that cause sunburn on human skin, by weighting UV exposure for action spectrum effects at a given time and location. This standard shows that most sunburn happens due to UV at wavelengths near the boundary of the UVA and UVB bands.
Sunburn effect (as measured by the UV index) is the product of the sunlight power spectrum (radiation intensity) and the erythemal action spectrum (skin sensitivity) across the range of UV wavelengths. [9] [10] The UV index is a number linearly related to the intensity of sunburn-producing UV radiation at a given point on the Earth's surface.
Parameters of interest, besides the wavelength of measurement, are absorbance (A) or transmittance (%T) or reflectance (%R), and its change with time. [4] [5] A UV-Vis spectrophotometer is an analytical instrument that measures the amount of ultraviolet (UV) and visible light that is absorbed by a sample. It is a widely used technique in ...
Typical F71T12 71-inch, 100-watt, bi-pin tanning lamp. Ultraviolet radiation (UVR) is part of the electromagnetic spectrum, just beyond visible light.Ultraviolet wavelengths are 100 to 400 nanometres (nm, billionths of a metre) and are divided into three bands: A, B and C. UVA wavelengths are the longest, 315 to 400 nm; UVB are 280 to 315 nm, and UVC wavelengths are the shortest, 100 to 280 nm.
Because UVC can be deadly, a special dichroic filter glass (usually purple) is required that will filter out the UVC and UVB. The goal with high-pressure tanning bulbs is to produce a high amount of UVA only. Unfiltered light from a high-pressure lamp is rich in UVC used in germicidal lamps, for water purification, but it damages human skin.
Blacklight fluorescent tubes. The violet glow of a blacklight is not the UV light itself, but visible light that escapes being filtered out by the filter material in the glass envelope. A blacklight, also called a UV-A light, Wood's lamp, or ultraviolet light, is a lamp that emits long-wave ultraviolet light and very little visible light.