From: astroelectronic@t-online.de   
      
   Phil,   
      
   thanks for your answer. Points 1 and 3 are clear. Point 2 is difficult to   
   understand for me. I have an input which is described by a 2x2 matrix, then I   
   make any operation which is also described by a 2x2 matrix, and the output is   
   also a 2x2 matrix. I    
   would understand it if input and output were vectors. Can a matrix be   
   multiplied by a matrix? I really need an example to see how this works. Any   
   idea where to find one?   
      
   Michael   
       
      
      
   > On 07/15/2015 02:26 AM, Michael Koch wrote:   
   > > Phil,   
   > >   
   > > I have a few questions about your book. The first question is about   
   > > formula 6.17 on page 204. If I set theta to 90°, then all four   
   > > matrix elements become zero, which means the analyzer passes no light   
   > > at all. I think that can't be correct.   
   >    
   > Right you are, thanks.  Lower right element should be sin**2.  (You put   
   > a rotation matrix on each side, with opposite angles.)   
   >    
   > > The next question is about formulas 6.20 to 6.24. Why are   
   > > polarization _states_ described by matrices, and not by vectors?   
   >    
   > Because it's possible for light to be partially polarized.   
   > Instantaneously the E field has a well-defined magnitude and direction   
   > everywhere, but in most cases both change randomly on femtosecond time   
   > scales.  You need more degrees of freedom to express partial polarization.   
   >    
   > > The last question is about formulas 6.22 and 6.23. Might it be   
   > > possible that in 6.22 a factor of 2 is missing in the denominator?   
   > > Please compare with Eugene Hecht: Optics, table 8.5 on page 323   
   >    
   >  From the definition (6.19), the normalizations should actually be E0**2    
   > (6.20 and 6.21), and EO**2/2 for the other three.   
   >    
   > Thanks again!   
   >    
   > Cheers   
   >    
   > Phil Hobbs   
   >    
   >    
   > --    
   > Dr Philip C D Hobbs   
   > Principal Consultant   
   > ElectroOptical Innovations LLC   
   > Optics, Electro-optics, Photonics, Analog Electronics   
   >    
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