Ultraviolet lys: Forskelle mellem versioner
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Solstrålingens indhold af UV afhænger i øvrigt af solhøjden, dvs. af den geografiske placering, årstiden og klokkeslættet. Farligst er det at opholde sig i ækvatoriale egne midt på dagen. I DK frarådes solbadning i tidsrummet 11-15 fra midten af maj til midten af august.
Det skadelige UVB-lys fra solen, trænger langt ned i klart vand. Da UVA-lys også er tilstede, betyder det, at vi faktisk kan blive brune under klart vand, dog bliver UV-lyset dæmpet en del, især hvis vandet er uklart af [[alge]]r eller andre partikler<ref>[http://www.albinism.org/publications/sunprotection.html Sun Protection] Citat: "...As much as 96% of ultraviolet rays can penetrate clear water..."</ref>
<ref>[http://www.who.int/mediacentre/factsheets/fs271/en/ WHO: Ultraviolet radiation: global solar UV index] Citat: "...Water offers only minimal protection from UV radiation, and reflections from water can enhance your UV radiation exposure..."</ref>
<ref>[http://ohioline.osu.edu/hyg-fact/5000/5550.html Sun Exposure: Precautions and Protection] Citat: "...Ultraviolet rays penetrate water but lose half their intensity. Nevertheless, burning can occur on parts of the body submerged in the water..."</ref>
<ref>[http://www.macam.com/refer.htm Fra: Penetration of solar UVB radiation in shallow tropical waters and its potential biological effects on coral reef; results from the central Indian Ocean and Andaman Sea. Richard P. Dunne, Barbara E. Brown. Department of Marine Science and Costal Management, University of Newcastle, Newcastle upon Tyne NE1 7RU, United Kingdom. Marine Ecology Progress Series Vol. 144: pp 109-118, 1996] Citat: "...Penetration of solar UVB radiation in shallow tropical waters and its potential biological effects on coral reef; results from the central Indian Ocean and Andaman Sea...Ed (UVB) at 5 m depth was found to decrease to 12% of the incident irradiance at the mid ocean atoll, to 2% for the high island site, and to 0.4% in the turbid waters of the inshore reef. A 1% Ed(UVB) depth was computed for each site and found to be 11, 6 and 3 m respectively..."</ref>
<ref>[http://www.yorku.ca/lel/ Amphibians and Ultraviolet Radiation] Citat: "...The more DOC [Disolved Organic Carbon], the less UVB that will penetrate beyond just the upper surface layers of water. For example, in a marsh with 13 mg C per liter of water, the surface level of UVB was reduced to 55% at just 1.4 cm deep; at 3.0 cm, the UVB was less than 5% of surface values, and at 5 cm depth, the UVB was just 2% of surface..."</ref>.
Viduesglas absorberer UVA og UVB, så man
Eksponering med UV er dog ikke udelukkende skadelig. Bl.a. dannes der gavnligt D<sub>3</sub>-[[vitamin]] i huden når den eksponeres for UV. Af samme grund anbefales mennesker med mørk hud eller tradition for tildækning med tøj at indtage D<sub>3</sub>-[[vitamin]] som kosttilskud.
Solbadning har en gavnlig virkning på visse hudforandringer og hudsygdomme. [[Niels Finsen]] var pionér på dette område. Han indførte bl.a. UV-behandling af hudtuberkulose i slutningen af 1800-tallet.
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