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Intensity for circular polarised light through linear polariser

  1. Feb 27, 2014 #1

    does the intensity change when circularly polarised light passes through a linear polariser?
    I am thinking of a flow like this: natural light -> vertical linear polariser -> quarter wave plate -> horizontal linear polariser -> intensity?

    After the first polariser, the intensity is 50%, the quarter wave plate changes the linear polarisation to circular. But does the horizontal linear polariser decrease the intensity again?

    Edit: Another flow would be natural light -> 45° linear polariser -> quarter wave plate -> - 45° linear polariser -> intensity? Since I think the polarisation is not affected by the quarter wave plate if the light is polarised vertically, I think the first flow would result in a complete absorption of the light by the second polariser (Intensity 0), right?

    Thank you.

    Last edited: Feb 27, 2014
  2. jcsd
  3. Feb 27, 2014 #2
    Yes, the second polariser cuts the intensity of the circular light in half.
    Last edited: Feb 27, 2014
  4. Feb 27, 2014 #3


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    Science Advisor

    ... and makes it linearly polarized.
    A plane polarizer treats circularly polarized light the same as it treats unpolarized light.
  5. Feb 27, 2014 #4
    Okay, thanks. That's what I thought. And this only works for the second flow I described, for the first one the quarter-wave plate would not change the polarization and would therefore practically be useless, right?
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