XPost: sci.physics, sci.electronics.basics   
   From: boxman@voyager.net   
      
   > There was an article in SciAm, ages ago, about a non-imaging optical   
   > system that could heat an object to above the sun's surface   
   > temperature. Sounds fishy, except that the sun does emit a lot of UV,   
   > energy past the black-body peak wavelength, which could be useful if   
   > concentrated enough. Like, 84,000:1.   
   >   
      
      
   Actually to be fair, the ratio you list (84,000:1) is the concentration   
   ratio provided by the system which can produce irradiance levels higher   
   than the sun.  There are no tricks used in regards to using UV energy or   
   something like that.  The absorber is simply immersed in an index of   
   refraction that is different from air.  The temperature of the abosrber   
   reached however will never exceed that of the sun as a blackbody since   
   the absorber immersed in a higher refractive index also radiates more   
   than one immersed in air, thus the temperatures remain equal in theory.   
      I don't think the SciAm article lists the temperature as being   
   higher, I think it talks about the irradiance being higher, which are   
   two different quantities.   See the following link for further details   
      
   http://www.solideas.com/papers/GPS_ThermCon_SEMSC.pdf   
      
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