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When evaluating ultraviolet germicidal lights, eye and skin health are primary concerns. UV-B, predominantly responsible for the harmful effects of sunlight, poses the highest risk for erythema, photokeratitis, sunburn and skin cancer. [15] [16] [17] While longer UV-C wavelengths and UV-A can also cause damage, their effects are less severe ...
Lengthening or extending a conjugated system with more unsaturated (multiple) bonds in a molecule will tend to shift absorption to longer wavelengths. Woodward–Fieser rules can be used to approximate ultraviolet-visible maximum absorption wavelength in organic compounds with conjugated pi-bond systems. [citation needed]
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.
Melanin is a chromophore that exists in the human epidermal layer of skin responsible for protection from harmful UV radiation. When melanocytes are stimulated by solar radiation, melanin is produced. [7] Melanin is one of the major absorbers of light in some biological tissue (although its contribution is smaller than other components).
Stokes formed the term from a combination of fluorspar and opalescence (preferring to use a mineral instead of a solution), albeit it was later discovered that fluorspar glows due to phosphorescence. [9] There was much confusion between the meanings of these terms throughout the late nineteenth to mid-twentieth centuries.
Usually the setup of a fluorescence assay involves a light source, which may emit many different wavelengths of light. In general, a single wavelength is required for proper analysis, so, in order to selectively filter the light, it is passed through an excitation monochromator, and then that chosen wavelength is passed through the sample cell.
Blood levels of folate, a nutrient vital for fetal development, can be degraded by UV radiation, [59] raising concerns about sun exposure for pregnant women. [60] Lifespan and fertility can be adversely affected for individuals born during peaks of the 11-year solar cycle , possibly because of UV-related folate deficiency during gestation.
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 ...