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The Benefits of UV Light Read and discuss all the great news about UV light and Vitamin D. |
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07-16-2006, 10:12 AM | #1 (permalink) |
Join Date: Feb 1 2006 Location: Tennessee Age: 62
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Rep Power: 103 | Light for dummies If you need technical information about light, this may help. Approximate wavelength (in vacuum) and frequency ranges for the various colors Color Wavelength (nm) Red 780 - 622 Orange 622 - 597 Yellow 597 - 577 Green 577 - 492 Blue 492 - 455 Violet 455 - 390 Frequency (THz) Red 384 - 482 Orange 482 - 503 Yellow 503 - 520 Green 520 - 610 Blue 610 - 659 Violet 659 - 769 1 terahertz (THz) = 103 GHz = 106 MHz = 1012 Hz, 1 nm = 10-3 um = 10-6 mm = 10-9 m. The white light is a mixture of the colors of the visible spectra. The electromagnetic and sound specta and their use for communication Wavelengths is a common way of describing light waves. Wavelength = Speed of light in vacuum / Frequency.The speed of light is the velocity of electromagnetic wave in vacuum, which is 300,000 km/sec. Light travels slower in other media, and different wavelengths travel at different speeds in the same media. When light passes from one media to another, it changes speed, which causes a deflection of light called refraction. The index of refraction, n, is defined as the following ratio: n = Speed of light in vacuum / Speed of light in a specific medium. Prefix:Symbol:Magnitude:Meaning (multiply by):Yotta- Y10241 000 000 000 000 000 000 000 000Zetta- Z10211 000 000 000 000 000 000 000 Exa- E10181 000 000 000 000 000 000 Peta- P10151 000 000 000 000 000 Tera- T10121 000 000 000 000 Giga- G1091 000 000 000 Mega- M1061 000 000 myria- my10410 000 (this is now obsolete) kilo- k1031000 hecto- h102100 deka- da1010 - -- - deci- d10-10.1 centi- c10-20.01 milli- m10-30.001 micro- u (mu)10-60.000 001 nano- n10-90.000 000 001 pico- p10-120.000 000 000 001 femto- f10-150.000 000 000 000 001 atto- a10-180.000 000 000 000 000 001 zepto- z10-210.000 000 000 000 000 000 001 yocto- y10-240.000 000 000 000 000 000 000 001 Uva is the closest Uv section to the visible spectrum. The UV spectrum is divided into Extreme UV (1-40nm) Vacuum UV (40-190 nm), Far UV (190-220 nm), UVC (220-290 nm), UVB (290-320), and UVA (320-400 nm). The shorter the wavelength, the higher the frequency.
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07-16-2006, 10:19 AM | #3 (permalink) |
Join Date: Nov 30 2000 Location: Ontario Age: 61
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Rep Power: 107 | Re: Light for dummies UVA is found in the region between 320 and 400 nm and is the least powerful wavelength band of UV radiation. UVA acts primarily to cause the melanin pigments in the skin to oxidize (darken) creating the cosmetic tan and has limited power to cause erythema. UVB is found in the region between 280 and 320 nm. It comprises the wavelengths primarily associated with erythema (sunburn), is also necessary for the production of vitamin D in the skin and is primarily responsible for stimulating increased melanin production. UVB wavelengths (at 305 nm) have 1,000 times more erythemal power than UVA wavelengths. UVC is found in the region between approximately 200-280 nm and is called germicidal UV because of its proven effectiveness in killing sing-cell organisms. Solar radiation in the UVC range is absorbed almost entirely by the atmosphere and that is fortunate considering that even a short overexposure to UVC is very harmful to the eyes and causes severe erythema (sunburn). One place where radiation in the UVC range can be found is in the arc of a welding torch. For that reason, optical damage referred to as "welders eye" is caused by UVC light. It should be noted that UVC wavelengths are not produced by the UVR sources utilized by the indoor tanning industry |
07-16-2006, 12:43 PM | #7 (permalink) |
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Rep Power: 43 | Re: Light for dummies So eeeehmmm tell me what should I do now???
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