Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Is the polarization of light relative?

  1. Jun 26, 2011 #1
    I was wondering if anyone had input into this question. Is the measured polarization of a beam of light relative to the frame of the observer?

    In the texts on Optics that I've read, there does not seem to be any reference to the observer's frame. It is only mentioned that light is Left-circularly polarized or linearly polarized, etc.

    When we describe polarization we ascribe to the light-beam in question a vector representing the polarized state. But is that polarized state the same for each observer?

    I am speculating that the polarization is relative and this is my (naive) reasoning.
    If we were discussing the path of a bullet, then in the frame of reference of somebody rotating, the path of the bullet would be curved. So the time dependent vector representing the path of the bullet would depend on the frame of reference of the observer.

    Now, the physics of light is so bizarre and I can barely understand it that I do not assume that the analogy between bullets and light can be taken very far. The point of the analogy though is that polarization state is described by a vector and similarly the path of the bullet. And since the mathematical abstraction that the vector represents depends on the reference frame for the bullet then I would assume that the polarization similarly depends on the reference frame of the observer as well.

    This is one of my problems in physics though. I am constantly in a wrestling match between distinguishing the mathematics from the physics.
  2. jcsd
  3. Jun 26, 2011 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    First consider the case of a massive spinning particle. Say that one observer says the particle is spinning like a right-handed screw going into a piece of wood, i.e., clockwise as seen from behind. Another observer who is traveling in the same direction as the particle, but faster, sees the particle as going backward, and therefore says it is spinning like a left-handed screw.

    It's different in the case of a massless particle. You can't overtake a massless particle, because massless particles travel at c.

    This is also why it's possible to have a law of physics that says that light is always transversely polarized. You can't have a constraint on the polarization of a massive particle, because there would be no way to define the constraint in the frame where the particle was at rest.
  4. Jun 26, 2011 #3
    I suppose you mean massless.
  5. Jun 26, 2011 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    No, I meant massive.
  6. Jun 26, 2011 #5
    Oh I see, you are talking about a constraint, took me a second the realize what you wrote.

    Sorry for that.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook