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Transmission of polarized light

  1. Feb 18, 2016 #1
    Today in lecture I learned that when light is polarized up and down (perpendicular to the plane of the incident beam) it is always reflected by some amount upon changing its medium of propagation, but when it is polarized side to side (parallel to the plane of the incident beam), there is an angle at which it can be transmitted 100% (Brewster's angle).

    I understand this in terms of the mathematical derivation, each step is understood and you can finally come up with a relation between the reflection coefficient and the incidence angle, and will see that for the perpendicular polarization case the coefficient is never zero, but for the parallel case the graph passes 0% reflection at a certain angle dependent on the indices of refraction.

    I am having trouble understanding it conceptually, however, and I feel that I should. My professor said that when you imagine the forced oscillation of the electrons caused by the incident electric field, and then their resulting electric field, you will see by the polarization that the opposing forced electric field can become 0, I assume not its magnitude but it can become perpendicular to the incident electric field. Can anyone help me understand this with an explanation, or a link, or a picture? I'm having trouble understanding why the phase of the reflected light also switches between parallel and perpendicular polarization.
     
  2. jcsd
  3. Feb 18, 2016 #2

    Henryk

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    Gold Member

    Here is a picture
    https://en.wikipedia.org/wiki/Brewster's_angle#/media/File:Brewsters-angle.svg
    Basically, the angle of reflection is exactly the same as the angle of incidence. The reflection is caused by the electric field created by the forced oscillations of electrons in the medium. The direction of oscillation is exactly the same as the direction of the electric field in the medium, that is perpendicular to the direction of the light propagation in the medium. When the angle between the direction of reflection and the refracted beam is exactly 90 degrees and the incident EM wave is polarized in the incidence plane, the electrons in the medium move parallel to the direction of reflection. Therefore, the field created by their forced motion has a zero component perpendicular to the direction of the reflection, and cannot induce a transverse EM wave.
     
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