From: pcdhobbs@gmail.com   
      
   >> Tip it a bit so it effectively isn't a full wave plate anymore, put it   
   between crossed   
   >>polarizers, and turn to get a dark fringe.   
      
   >That sounds like a good idea, but my FWP doesn't behave as expected. When I   
   turn it   
   >between crossed polarizers, it changes color between pink and green. Tilting   
   doesn't change   
   >much. Then it's more pink than green.   
      
   Wave plates are dispersive, because to leading order they give you a time   
   delay between polarizations rather than a constant phase shift. Thus you have   
   to pick a wavelength. A red laser pointer is a reasonable source for this.   
      
   Cheers   
      
   Phil Hobbs   
      
   --- SoupGate-Win32 v1.05   
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