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Homework Help: Light polarization (lab questions)

  1. Nov 2, 2008 #1
    1. The problem statement, all variables and given/known data
    I just have a few of questions about light polarization. We never discussed polarization in class, so I am slightly confused on a couple of questions.

    For the Experiment we used polarization filters. If I understood the difference between partially and completely polarized light, that would help a lot.

    1) Was the light emerging from the first polarization filter polarized?
    2) What did you observe when you viewed the light through the analyzer?
    3) How can you tell if the light is partially or completely polarized?
    4) What did you observe about light that is reflected off of a surface?

    *Look in the direction that is 90 degrees from the sun, and rotate the filter*

    5) Is the light from the sky partially polarized? How can you tell? Would you describe the light as totally or partially polarized?
    6) Explain the atmospheric scattering and describe how the light from the sky becomes polarized
    7) Explain why polarized sunglasses are useful. Why is there a law limiting the percent polarized (about 95% in prescription sunglasses.

    2. Relevant equations
    3. The attempt at a solution
    This is what I have so far...
    1) Yes
    2) Less light is able to get through the filter.
    3) I don't know...unless completely polarized light means no light gets through...which requires 2 filters.
    4) There is less glare.

    5) The light is polarized, but I have no idea if it is partially or completely
    6) no idea
    7) Polarized sunglasses can be used to reduce glaring, which makes it easier to see. I assume if the glasses have 100% polarization, then no light gets through...which means you can't see.
  2. jcsd
  3. Nov 3, 2008 #2
    Can anyone explain to me the difference between partially and completely polarized light?
  4. Nov 3, 2008 #3
    Completely polarized means that *every* photon in the light beam has the same polarization. Or, more operationally, there is one polarization filter that would let *all* of the light go through.

    Partially polarized light does not quite have these properties.
  5. Nov 3, 2008 #4
    So in that case, would that mean that one filter has complete polarization and 2 filters is partial polarization?
  6. Nov 3, 2008 #5
    I don't know what "one filter has complete polarization" means. Light has polarization, the filter doesn't "have" polarization. Nor do I know what "2 filters is partial polarization" means.

    And now I gotta run....sorry.
  7. Nov 3, 2008 #6
    Thanks for trying to help me.
    Hm...let me try and be a little bit more clear.

    What I was trying to say, is the light passing through a single filter or two filters, is that light partially or completely polarized?
  8. Nov 3, 2008 #7
    The light that has passed any number of polarization filters should be completely polarized. That's why it's called a filter :-)
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