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U

(U band)
(photometric filter for ultraviolet light)

The letter U (or U band) is commonly used to indicate a passband located in the ultraviolet range (U for ultraviolet), typically for one located not far from the visible light range. The letter is also often used for a filter for the band (or more explicitly, a U filter), and to indicate a magnitude of a signal observed through such a filter, e.g., citing "u = 1.5".

In the conventional UBV photometric system and its offshoots, the U band is centered around wavelength 365 nm, with a width of 66 nm (full width at half maximum). Other systems may have different specifications, sometimes similar.


(EMR,ultraviolet,band,photometry)
http://en.wikipedia.org/wiki/Photometric_system
WaveLFreqPhoton
Energy
  
365nm821THz3.4eVU

Referenced by:
color-color diagram
color index
passband
SkyMapper Southern Survey (SMSS)
UBV photometric system
Vega

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