I understand that light from stars is coherent and can be treated   
   as a plane wave. I wonder how can I calculate the amplitude A of   
   such plane wave A exp[ct-kx] for a given star form its magnitude,   
   bandwidth, distance and other parameters of the star.   
      
   What is the typical range for A for a typical wavelength?   
      
   Thanks   
      
   [[Mod. note --   
   1. The light from a star is *incoherent* -- each of the huge number   
      of atoms in the star's photosphere is radiating independently, and   
      the light we receive is (that tiny fraction that happens to be   
      radiated in our direction) the incoherent sum of light from many   
      of those atoms.   
   2. The light from a star is coming from very far away, so to a *very*   
      good approximation it can be treated as a plane wave.   
   3. The amplitude of a plane wave is directly related to the intensity   
      of the light, i.e., how bright the star is.  The book "Astrophysical   
      Quantities", by Allen, has numbers for home many photons/second   
      per square centimeter of detector area we receive for a given   
      magnitude star, but I don't recall these offhand.  Converting to   
      an amplitude of a plane wave takes a little bit more algebra...   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)