What is UV radiation?
UV is short for Ultra Violet, which means beyond violet. It was first dicovered in 1801 by a German physicist caled Johann Wilhelm Ritter, who made the hallmark observation that invisible rays just beyond the violet end of the visible spectrum darkened silver chloride-soaked paper more quickly than violet light itself.
UV radiation AMost of us are exposed to large amounts of UVA throughout our lifetime. 95 percent of the of the UV radiation reaching the Earth its surface is UVA. While UVB is much more intence than UVA, UVA rays are 30 to 50 times more prevalent. The intensity doesn't really change over the hours with sunlight over the entire year, and these rays can also penetrate clouds and glass.
UVA penetrates the skin more deeply than UVB. This has long been known to play a major part in skin aging. Though, until recent studies scientistts believed it did not cause any significant damage in areas in the epidermis (outer layer of the skin) where most skin cancers occur. These studies over the past two decades do show that UVA damages skin cells called keratinocytes in the basal layer of the epidermis, where most skin cancers occur. (Basal and squamous cells are types of keratinocytes.) UVA contributes to the development of skin cancers. It might even be the whole cause. UVA is the dominant tanning ray, and we now know that when we tan, outdoors or in a salon, it will cause cumulative damage over time. Especially the DNA is harmed a lot. The skin will try to prevent further damage by darkening the skin. By this isn’t a perfect way and the DNA will still be damaged which causes mutations and/or imperfections can lead to skin cancer. Tanning booths primarily emit UVA. The high-pressure sunlamps used in tanning salons emit doses of UVA as much as 12 times that of the sun. Not surprisingly, people who use tanning salons are 2.5 times more likely to develop squamous cell carcinoma, and 1.5 times more likely to develop basal cell carcinoma. According to recent research, first exposure to tanning beds in youth increases melanoma risk by 75 percent. http://www.skincancer.org/prevention/uva-and-uvb/understanding-uva-and-uvb The positive side of UVRUVB rays do have a positive effect, namely that because of them the skin produces vitamin D. When the UVB rays get in contact with a molecule in the skin they produce vitamin D. We need vitamin D for healthy bones and to absorb calcium. This seems like a great thing but we why would you expose yourself to uv radiation while you can also get vitamin d from some specific food types and supplements.
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UV radiation BUVB is the main cause of skin reddening and sunburn. It tends to damage the skin's upper layers, the more superficial epidermal layers. It plays a dominant role in the development of skin cancer and a small role in tanning and photo aging. The intensity of UVB rays varies by season, by the location and by the time of day. The most significant amount of UVB hits the U.S. between 10 AM and 4 PM from April to October. However, UVB rays can burn and damage your skin year-round. This is especially the cast at high altitudes and on places with a reflective surfaces such as snow or ice. These bounce back up to 80 percent of the rays. Because of this they can hit the skin twice. Though, UVB rays are not able to penetrate glass.
UV radiation and skin colorWhen you would travel from the north pole towards the south pole, you would see different cultures, temperatures but also different skin colors. The closer you get to the equator, the darker the skin. This has do with natural selection. Around the equator there is much more sun and the people who live there are exposed to a lot more ultraviolet radiation then people who for example live in Great Britain of the Netherlands. Their dark skin color actually protects them against most of the ultraviolet radiation as it absorbs less of it. Although this is good for them, this also results in them not producing a lot of vitamin d.
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UV radiation CUV-C rays are not able to reach the Earth because they can’t penetrate the ozone layer. This is because when the UV-C rays meet the ozone molecules at high layers of the atmosphere, the energy inherent in them is enough to break apart the bond of the molecule and absorb the energy. Because of this no UV-C rays from the sun will ever come into contact with life on earth. Though, man-produced UV-C rays can be a harmful in certain professions, such as welders.
Johann Wilhelm RitterJohann Wilhelm Ritter (16-12-1776 t/m 23-01-1810) was a famous German scientist, physicist and philosopher. He discovered ultraviolet when he was experimenting with silverchloride. Silverchloride turns black when exposed to sun. He placed the silverchloride in the area just behind the violet end. Although no visible light can be seen behind the violet end of the spectrum, a reaction occurred. This was the first time there was prove for these invisible rays. Ritter himself called the rays Chemical Rays, but later this name was changed to Ultraviolet rays.
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