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Question about polarization

  1. May 13, 2010 #1


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    I'd like to test my understanding of polarization, concept new to me. I except that the answer to my following question is "no", but I'm not sure and I don't know why it would be so.
    If I see a circularly (left of right, it doesn't matter) polarized EM wave going to my eyes and I put a polaroid in front of my eyes such that it polarizes linearly the light. Will the EM wave getting on my retina be a continuous wave? I'd think that no since the polaroid would absorb most of the light and let only pass the wave when the electric and magnetic fields have a very particular direction. So only a small part of the incoming wave would pass through the polaroid, making a discontinuous wave. Is my reasoning erroneous? I guess that yes, but I need an explanation.
    In other words, would my retina be constantly receiving some EM wave? I think that most of the time, no. Am I right?
  2. jcsd
  3. May 13, 2010 #2
    Imagine a long rope or string, holding one end while the other is tied off. You can send linear polarised waves along it by shaking your end up and down. You can send circ. pol. waves by shaking the end in a circle. If the string passes through a narrow vertical gap, like a door jam, what kind of wave gets through the jam if you try sending a) circular b) vertical c) horizontal polarisations? (And does anything get reflected?)
  4. May 13, 2010 #3

    Andy Resnick

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    Circular polarization is the sum of two linear polarization states, each in quadrature to each other. So the field passing through a linear polarizer is one of the two states, which has a time-dependent amplitude and intensity [sin(wt) or sin^2(wt)]. This is not a discontinuous wave, tho.
  5. May 13, 2010 #4


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    Thanks both for helping,
    I have a language difficulty, I tried google translator and wikipedia, but I can't figure out what a door jam is and I have a vague idea about what a vertical gap is.
    So I can't really answer, but my intuition tells me that b passes, c doesn't and I'm not sure what happens with a.

    I see. I'd have to read more about it, I can't picture in my head what's going on.
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