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The Sun's UV output is divided into UV-A and UV-B: solar UV-A flux is 100 times that of UV-B, but the erythema response is 1,000 times higher for UV-B. [citation needed] This exposure can increase at higher altitudes and when reflected by snow, ice, or sand. The UV-B flux is 2–4 times greater during the middle 4–6 hours of the day, and is ...
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The cheaper and more common 395 nm UV LEDs are much closer to the visible spectrum, and give off a purple color. Other UV LEDs deeper into the spectrum do not emit as much visible light. [ 43 ] LEDs are used for applications such as UV curing applications, charging glow-in-the-dark objects such as paintings or toys, and lights for detecting ...
In 2009, Natural Resources Canada released a report [14] describing the possible UV exposure from several types of lamps. The report states that at 3 cm distance, the recommended daily exposure to ultraviolet radiation for skin and eye damage (if looking directly at the lamp) was attained between 50 minutes and 5 hours depending on the type of ...
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.
[45] [failed verification] UVC is the highest-energy, most-dangerous type of ultraviolet radiation, and causes adverse effects that can variously be mutagenic or carcinogenic. [46] Despite the importance of the sun to vitamin D synthesis, it is prudent to limit the exposure of skin to UV radiation from sunlight [47] and from tanning beds. [48]
A downconversion from ultraviolet to visible is possible, as is conversion between visible wavelengths (e.g., green to orange) or visible to near-infrared. The shift can be as much as 200 nm, but usually the range is about 20–100 nm longer than the absorption spectrum. [21]
The ozone layer also blocks most, but not quite all, of the sunburn-producing UV-B (280–315 nm) band, which lies in the wavelengths longer than UV-C. The band of UV closest to visible light, UV-A (315–400 nm), is hardly affected by ozone, and most of it reaches the ground. UV-A does not primarily cause skin reddening, but there is evidence ...