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    Re: Sextants with Polarizing filters
    From: Peter Fogg
    Date: 2006 Jan 27, 07:49 +1100

    ________________________________________
    Jim Hickey wrote:
    "Quantum mechanics and celestial nav, what a mix!"
    
    For an explication without recourse to quantum mechanics:
    http://alienryderflex.com/polarizer/
    that finishes: "So there you have it!  No spooky quantum properties.
    Nothing very mysterious about it, in fact.  A straightforward chain of cause
    and effect, yielding rational, comprehensible results."
    
    Another site that deals with this in terms of the Law of Malus is
    http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polcross.html
    that states that: "If the center polarizer is placed at 45? between crossed
    polarizers, 25% of the light will be transmitted."
    
    Googling with "third polarizer" turns up lots of sites. One, from a high
    school in Maine, even uses the poor old picket fence analogy, going on to
    state:
    "The middle one re-steers the polarized wave to have vibrations
    somewhat in the direction that the last one will pass."
    http://www.iit.edu/~smile/ph96m6.html
    
    This idea seems popular, presumably because it is understandable (kind of!)
    even if Jim Hickey's site specifically warns against such imaginings.
    Eg:
    "then ... take a third and insert it between the two at say, 45o ... more
    light will come through than with the two anti-parallel polarizers. This
    would logically require that the third polarizer "rotate" the angle of
    polariztion of some of the light which has passed the first polarizer ...
    thus allowing it to go through the third." from
    http://www.ebtx.com/ntx/polaroid.htm
    
    
    

       
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