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Average UV at noon 1996-2002 (European Space Agency) The ultraviolet index, or UV index, is an international standard measurement of the strength of the sunburn-producing ultraviolet (UV) radiation at a particular place and time. It is primarily used in daily and hourly forecasts aimed at the general public.
The sun protection factor (SPF rating, introduced in 1974) is a measure of the fraction of sunburn-producing UV rays that reach the skin. For example, "SPF 15" means that 1 ⁄ 15 of the burning radiation will reach the skin, assuming sunscreen is applied evenly at a thick dosage of 2 milligrams per square centimeter [65] (mg/cm 2). It is ...
The following table is listing suggestive relations of the lightfastness ratings on different measure scales and the relation relative to time in direct sunlight and normal conditions of display: away from a window, under indirect sunlight and properly framed behind a UV protective glass. [10]
A relatively new rating designation for sun protective textiles and clothing is UPF (ultraviolet protection factor), which represents the ratio of sunburn-causing UV measured without and with the protection of the fabric. For example, a fabric rated UPF 30 means that, if 30 units of UV fall on the fabric, only 1 unit will pass through to the skin.
The five ratings for transmittance (filter) under this standard are based on the amount of absorbed light, 0 to 4, with "0" providing some protection from UV radiation and sunglare, and "4" indicating a high level of protection, but not to be worn when driving.
Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight, and constitutes about 10% of the total electromagnetic radiation output from the Sun.
UV-B, predominantly responsible for the harmful effects of sunlight, poses the highest risk for erythema, photokeratitis, sunburn and skin cancer. [16] [17] [18] While longer UV-C wavelengths and UV-A can also cause damage, their effects are less severe than UV-B. In contrast, far-UVC has shown remarkably different results.
Zero denotes extremely poor colour fastness whilst a rating of eight is deemed not to have altered from the original and thus credited as being lightfast and permanent. The ultraviolet (UV) radiation in light is responsible for ink fading. As the intensity of UV radiation differs from place to place, the ink fading also depends on place.