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Solar spectrum. The three wavelength ranges along the solar radiation spectrum that are relevant for their impact on skin are ultraviolet (UV), visible light (Vis) and Infrared A (IRA). Energy and penetration properties are respectively lower and higher with increasing wavelengths. In the UV wavelengths domain UVA1 (long UVA), 340–400 nm can represent up to 80% of the total UV rays (for example, in the winter in temperate zones). UV: ultraviolet; IRA: Infrared A.
