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What does the Three Polarizer Experiment prove?
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What does the Three Polarizer Experiment prove?
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What does the Three Polarizer Experiment prove?
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26/03/2024 04:35:37 »
If the results of The Double Slit Experiment sound weird, there is yet another experiment that demonstrates quantum mechanics effects, that trumps everything else. As far as proofs of quantum mechanics goes, the 3 polariser experiment may be considered to be the ace in the hole.
It should be remembered here, that polarization is not an intrinsic property of light per se. Polarisation is the property of a substance that polarises light that passes through it. This is similar to saying that a laminar flow, is not an intrinsic property of water, a laminar flow of water is the result of certain conditions being imposed on the water as it passes through a space. Historically, the polarisation of light was first observed in naturally occurring crystals such as calcite or quartz. These crystals both demonstrate the property of birefringence, or changing of the direction of the incoming light. Later, the same effect was duplicated by stretching plastic like materials causing the molecules to form into long lines or chains. When iodine was added to the molecules, they effectively absorbed light falling on the chains of molecules blocking it, while allowing orthogonally oriented light to pass through. If the polariser is effective, it blocks 50% of the light.
The experiment is as follows, three polarisers are used, hence the name of the experiment. When a light is shone through a vertical filter (let's call it Filter 1) and then through another vertical filter (Filter 2 also called the analyser in QM), all of the light that passes through the first filter will also pass through the second filter. This is because both filters are aligned with the same orientation, so they allow light with the same polarization to pass through.
However, if the polarisers are good and a horizontally oriented filter is put in place after the vertical polariser, it is found that light passing through both filters is completely blocked. No light passes through to the other side of the horizontally oriented filter.
This big mystery arises from the fact that if a third diagonally oriented polariser is placed between the first two polarisers, light is again allowed to pass through. Although the intensity of the light is reduced in keeping with malus law where the intensity is equal to the square of the cosine of the angle made between the transmission polariser and the analyser polariser is multiplied by the initial intensity.
The quantum mechanics explanation for this phenomenon is superposition, and it is deemed to be the final proof of quantum mechanics. Therefore, according to this explanation, light has a definite polarisation (a) horizontal or (b) vertical, when it undergoes diagonal polarisation it is in a superposed state, having elements of both vertical and horizontal orientation, and hence can pass through either the vertical or the horizontal with its intensity reduced according to malus law.
However, there is a simpler explanation if one looks at the polariser as a diffraction grating. The size of the molecules forming linked chains make this alternative a distinct possibility, as they would diffract the light without dispersing it. One result of this is that the vertical component is blocked or absorbed by the chains of molecules, while the remaining vertical component of the light is diffracted in a horizontal direction. Therefore, only the horizontal component of light is present after it passes through the vertical filter (i.e., chains of molecules oriented in a vertical direction) . If a horizontal filter (i.e., chains oriented horizontally or orthogonal to the first filter) is now placed in the light coming from the vertical filter all of the light will be blocked and no light shall pass the horizontal filter.
What happens when a diagonally oriented filter( i.e., chains of molecules oriented diagonally) is placed between Filter 1 and filter 3? Some of the light coming through Filter 1 is blocked by the diagonal chains of molecules but the remaining light undergoes diffraction at a diagonal angle and the light reduced according to malus law, makes it not only through the diagonally oriented filter but through the horizontal filter, although undergoing a further reduction in intensity in the process.
So, no great mystery, it all depends on the direction of the light as mentioned at the beginning of the post.
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Re: What does the Three Polarizer Experiment prove?
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26/03/2024 08:54:29 »
If you set up a radio transmitter with a simple dipole antenna, the polarisation is the axis of the dipole.
If you move towards that antenna very quickly, the radio waves are blue-shifted into light.
So you are wrong to say "it should be remembered here, that polarization is not an intrinsic property of light per se. "
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