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UV Light

  1. Mar 2, 2005 #1
    Does anyone know the range of the wavelengths of the UV light that reaches the earth (ground)?
  2. jcsd
  3. Mar 2, 2005 #2


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    Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than visible light, but longer than that of soft X-rays. It can be subdivided into near UV (380–200 nm wavelength) and extreme or vacuum UV (200–10 nm). UV wavelengths are also often subdivided into UVA (380–315 nm), also called Long Wave or "blacklight"; UVB (315–280 nm), also called Medium Wave; and UVC (280-10 nm), also called Short Wave or "germicidal".

    The name means "beyond violet" (from Latin ultra, "beyond"), violet being the color of the shortest wavelengths of visible light.

    The Sun emits ultraviolet radiation in the UVA, UVB, and UVC bands, but because of absorption in the atmosphere's ozone layer, approximately 99% of the ultraviolet radiation that reaches the Earth's surface is UVA (380–315 nm). UVC is partially responsible for the generation of ozone as well, and most of the remaining 1% is extream/vacuum UV (200-10 nm)
  4. Mar 2, 2005 #3
    Why would the UVA light enter the atmosphere while UVC interacts with it. To me, it would make sence if it was the other way around. The larger wavelength ultraviolet light (UVA) would not make it through since the distance between molecules in the atmosphere is not enough to let the light through, while the UVC light, which is of a smaller wavelength, should enter (just like sunlight-blue enters while red doesn't). Is it bcause the UVS wavelength is soo small that the waves actually interact with particles in the atmosphere and cannot pass by them?
  5. Mar 2, 2005 #4

    Size is not the dominant mechanism, resonance is (absorbtion/emission). Some UV's are absorbed (blocked) by the atmosphere, while others are re-emitted (enter). Red does enter, otherwise we could not see red here.

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