Ultraviolet Radiation
The gases which make up the sun are mostly hydrogen with about 10% helium and other elements. A constant nuclear reaction in the core of the sun changes the hydrogen to helium and then releases tremendous amounts of energy in the form of electromagnetic radiation. Put simply, this radiation travels through space in the form of waves. And, like ocean waves, some of the rays are short and fast (x-rays) some are midsize (visible light) and others are very long (radio waves). The entire range of these different wavelengths makes up the electromagnetic spectrum. Ultraviolet radiation or UV falls in the middle and includes UVC, UVB and UVA.
UVC are sunrays with wavelengths between 100 and 280 nm. These rays are referred to as germicidal radiation because they kill microorganisms including bacteria. UVC is the shortest UV wavelength, and the most intense. It is completely absorbed by the stratosphere, ozone and atmospheric gases so the only sources on earth are artificial.
UVB are sunrays with wavelengths between 280 and 315 nm. These rays represent only two percent of the sun's energy and are partially absorbed by the ozone layer. Fifteen percent of the UVB entering the atmosphere reaches the earth's surface. Even in small amounts, UVB can create sunburn and is a major threat to our skin. UVB accounts for the vast majority of skin damage and causes premature aging and skin cancers. UVB is present in a higher concentration when the sun is more directly overhead and closest to the earth's surface i.e. noon time and summer.
UVA are sunrays with wavelengths of 315 to 400 nm. UVA has the longest wavelength of UV and are the least powerful rays. However, when striking the surface of the skin, UVA has been shown to penetrate more deeply than UVB, potentially causing greater harm. There is 30 to 50 times as much UVA as UVB reaching the earth's surface, depending on the time of year. UVA is present all day long and all year long in nearly similar levels.
Ultraviolet radiation damages our skin. Exposure to the combination of UVB and UVA is an attack on the skin. It hits at multiple levels creating damage that ranges from sunburn to chromosomal damage, to premature aging, to malignant melanoma.
UV protection is very important as it doesn't take more than 20 minutes unprotected exposure to begin the damage for many people.
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