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Polarization Question

  1. Feb 8, 2007 #1
    1. The problem statement, all variables and given/known data
    Light reflecting off most outdoor surfaces such as roadways and bodies of water have less vibrations perpendicular to the surface than parallel to it. What type of polarizing lens would be the most effective at minimizing the glare off these surfaces?


    2. The attempt at a solution
    This question seems poorly constructed. I know that 2 perpendicular polarizers stacked on top of each other will restrict light... but I really don't understand what it is they are asking. Any insights?

    Cheers
     
  2. jcsd
  3. Feb 8, 2007 #2

    Dick

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    Perhaps it is confusing. I think what they want is what should the polarization direction in the lens be.
     
  4. Feb 8, 2007 #3
    Hi Dick,

    Could they be referring to linear type polarization filter vs circular type? We did not cover circular or linear so I would be hard-pressed to think that this is what they meant by it... but I think ur right, "DIRECTION" is what they meant by it...

    so basically they are saying that light reflects parallel to the surface of reflection?! Good lord... how does that make any sense?
     
  5. Feb 8, 2007 #4

    Dick

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    They are saying that the dominant polarization of reflected light is parallel to the surface. And it's true. Did you ever own a pair of the aptly named "Polaroid" sunglasses?
     
  6. Feb 8, 2007 #5
    Thanks for the reply :)

    Actually no I never owned a pair. I don't see how it is reflected parallel to the surface. Light is reflected in ALL directions from what I understand isn't it? If a surface is going to reflect light predominantly parallel to itself then the source of light must also be close to the surface of reflection.

    Consider for example the sun during sunset... since it is close to the surface, the reflection streaks out over the entire surface of the ocean. This is the only way I can see it being parallel to itself... but then again this is relative to the "point of view" isn't it? If I view the same sunset situation from space I won't see JACK...
     
  7. Feb 8, 2007 #6

    Dick

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    Ok, so your lack of experience is to blame :smile:. I'm not saying anything about the direction in which light is reflected. I'm talking about its polarization. Take that silvery reflection from the road ahead on a hot day. Put a pair of these on and it almost entirely goes away. Rotate the lens 90 degrees and it comes back. What effect am I seeing? It's REALLY TRUE.
     
  8. Feb 8, 2007 #7
    Ahhhhh ok :) Hummmm.. this is interesting actually. Makes me want to get a pair of polarized sunglasses! Ok, so this means that the predominant parallel vibrations as they put it, coming off the road are somehow already "polarized" in a sense? This means that the sunglasses are polarized in such a direction as to prevent the reflections from passing the sunglasses right? But what determines the direction? Why does it work one way and not the other?
     
  9. Feb 8, 2007 #8

    Dick

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    I think by 'parellel vibrations' they mean the axis of polarization is parallel to the road surface. If I want to eliminate it, how should you orient the polarization axis of the lens? What would happen if I rotate the lens 90 degrees? Do get a pair, you can also do interesting tricks with cellophane type plastics. Kept me amused for hours on end...
     
  10. Feb 8, 2007 #9
    so, the vibrations resemble a snake slithering (in a sine wave fashion) on the road right? The lens would then have to be polarized vertically, or perpendicularly to the "parallel vibrations" in order to minimize vibrations. Did I hit that one on the head?

    PS. I am soo getting a polarized pair of shades... :)
     
  11. Feb 8, 2007 #10

    Dick

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    Yes. Don't forget to rotate them.
     
  12. Feb 8, 2007 #11
    haha awesome! Thanks for the guidance...

    All the best :)
     
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