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Old May 30th 2008, 08:42 PM   #1
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Polarization

When light passes a polarizer, the light beam is said to be plane polarized. So that is the principle behind for the polarizer?

Does the polarizer absorbs some light in other planes? Or simply because they are not allowed to pass through? If the former is the reason, why not light in all planes are absorbed but with one plane not absorbed?If it is the latter reason, then there should be some reflections in the polarizer, right?



I don't understand why polarization can be done by reflection and refraction. Is there special principle behind which differs from that of polarization by selective absorption?
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Old May 31st 2008, 07:51 AM   #2
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Originally Posted by werehk View Post
When light passes a polarizer, the light beam is said to be plane polarized. So that is the principle behind for the polarizer?

Does the polarizer absorbs some light in other planes? Or simply because they are not allowed to pass through? If the former is the reason, why not light in all planes are absorbed but with one plane not absorbed?If it is the latter reason, then there should be some reflections in the polarizer, right?



I don't understand why polarization can be done by reflection and refraction. Is there special principle behind which differs from that of polarization by selective absorption?
We may consider a single wave of light to be "oscillating" in one plane. This is said to be the plane of polarization of that light. Most light sources produce random polarization of the light emitted: the planes of polarization are randomly distributed.

A polarizer is a device (usually made from photographic film in my experience, but there are rock crystals that produce a similar effect) that allows only one plane of polarization to pass through. I have never heard anyone talk about the "back side" of the polarizer. I would imagine some of the incident light is absorbed and the rest reflected. The situation is rather like a fence made from slats of wood that are spaced evenly. If you pass a rope through the gaps and shake it you will find that only oscillations in the plane of the gaps will be allowed through, while the rest of them don't.

I have never heard of a polarizer refracting light. That simply isn't how the thing works.

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Old May 31st 2008, 08:51 PM   #3
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For a book I have read,"MODERN PHYSICS",
It suggested that an example of polarization by refraction is that unpolarized light exhibits double refraction when it strikes the crystal surface, when the two refracted light beams produced by double refraction come out, two light beams are plane polarized.

Is it the same principle as that of common polarizer?
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Old Jun 1st 2008, 04:54 AM   #4
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Originally Posted by werehk View Post
For a book I have read,"MODERN PHYSICS",
It suggested that an example of polarization by refraction is that unpolarized light exhibits double refraction when it strikes the crystal surface, when the two refracted light beams produced by double refraction come out, two light beams are plane polarized.

Is it the same principle as that of common polarizer?
I have heard of the phenomena, it's what I mentioned briefly in my first post, but I really have no understanding of it. If it is truly a refraction phenomenon then I would say that the incoming light has its polarization changed, as opposed to some being blocked: refraction is not a process where light energy is typically lost.

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Old Nov 18th 2009, 06:14 PM   #5
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A polarizer can separate two polarizations of the light to different directions of the beams.
There are major two kinds of polarizers, one is absorb one polarization of the light and keep only the other polarization of the light not absorption.
The other kind of polarizer is change the direction of one polarization of the light, e.g reflection (PBS), and keep the other polarization light go to a different direction.
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