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  4. How to demonstrate polarization of light?
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How to demonstrate polarization of light?

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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #40 on: 04/10/2022 03:47:02 »
Quote from: Deecart on 03/10/2022 16:33:41
Quote from: hamdani yusuf on 21/09/2022 04:15:46
I don't think that I have to reinvent the wheel. So far, the model I used here haven't lead to contradiction.

There is not even a contradiction because the representation used by the model is totaly unaccurate.
It is like everybody mimic the same representation, avoiding the understanding of the occupation of space by the field(s) (In my opinion)





What's the more accurate model in your opinion?
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Offline William Hardy

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Re: How to demonstrate polarization of light?
« Reply #41 on: 14/12/2022 16:07:17 »
Sunglasses!
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #42 on: 15/12/2022 08:08:52 »
Quote from: William Hardy on 14/12/2022 16:07:17
Sunglasses!
Not all sunglasses are polarizing.
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #43 on: 07/08/2023 23:00:32 »
A good demonstration of how 3d glasses of circular polarization type work.

I already have two pairs of circularly polarized 3d glasses. I think I can make some interesting experiments with them.
« Last Edit: 07/08/2023 23:05:30 by hamdani yusuf »
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #44 on: 07/08/2023 23:03:55 »
If you want to compare various types of 3d glasses, just watch this video.
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #45 on: 18/08/2023 12:53:52 »
This is an example how circular polarizer is understood in the community of photography.

CPL Filters Explained! - What It's Used For, How They Work

But there are some errors and incomplete information that may confuse the viewers. Can you find them?

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« Last Edit: 18/08/2023 13:03:00 by hamdani yusuf »
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #46 on: 18/08/2023 13:10:05 »
Here's one clue for one of the errors.
https://en.wikipedia.org/wiki/Polarizer#Absorptive_polarizers
Quote
A Polaroid polarizing filter functions similarly on an atomic scale to the wire-grid polarizer. ...
https://en.wikipedia.org/wiki/Polarizer#Wire-grid_polarizers
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #47 on: 18/08/2023 15:17:26 »
There's one comment on the YouTube video which I think more people should know.
Quote

Good general explaination of polarizing filters, what function they provide, and how to apply that to improve your images.  One small correction however.   There is a difference between linear polarizing filters and circular polarizers.  Prior to the advent of digital cameras, and particularly prior to autofocus cameras, virtually all photographic polarizing filters were linear.  They function pretty much as you describe.  What was quickly discovered was this type of filter confuses and disables the autofocus feature.  The remedy was to add a second layer, after the linear polarizer, to essentially "twist" all the light into different polarization angles.  Now the beam-splitter for the autofocus can work again.  This quarter-wave plate is on the threaded side of the CPL, closest to the camera.  If you look through a "normal" (linear) polarizing filter from either side you can have the same effect.  With a CPL the suppresion of the reflections only work from one side.
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #48 on: 19/08/2023 15:35:57 »
Quote from: hamdani yusuf on 18/08/2023 12:53:52
This is an example how circular polarizer is understood in the community of photography.

CPL Filters Explained! - What It's Used For, How They Work

But there are some errors and incomplete information that may confuse the viewers. Can you find them?

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In 1:40, he only explain the need for linear polarization. The comment I quoted above explains why circular polarizer is needed.
« Last Edit: 19/08/2023 15:44:42 by hamdani yusuf »
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #49 on: 19/08/2023 16:58:41 »
Quote from: hamdani yusuf on 18/08/2023 13:10:05
Here's one clue for one of the errors.
https://en.wikipedia.org/wiki/Polarizer#Absorptive_polarizers
Quote
A Polaroid polarizing filter functions similarly on an atomic scale to the wire-grid polarizer. ...
https://en.wikipedia.org/wiki/Polarizer#Wire-grid_polarizers



This is contrary to the diagram shown in the video at 2:33.
« Last Edit: 19/08/2023 17:02:15 by hamdani yusuf »
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #50 on: 21/08/2023 03:15:35 »
This is how circular polarizers work.
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Circular polarizers (CPL or circular polarizing filters) can be used to create circularly polarized light or alternatively to selectively absorb or pass clockwise and counter-clockwise circularly polarized light. They are used as polarizing filters in photography to reduce oblique reflections from non-metallic surfaces, and are the lenses of the 3D glasses worn for viewing some stereoscopic movies (notably, the RealD 3D variety), where the polarization of light is used to differentiate which image should be seen by the left and right eye.
https://en.wikipedia.org/wiki/Polarizer#Circular_polarizers


And this is how the same device can be used as the analyzer.
https://en.wikipedia.org/wiki/Polarizer#Absorbing_and_passing_circularly_polarized_light
Quote
Circular polarizers can also be used to selectively absorb or pass right-handed or left-handed circularly polarized light. It is this feature which is utilized by the 3D glasses in stereoscopic cinemas such as RealD Cinema. A given polarizer which creates one of the two polarizations of light will pass that same polarization of light when that light is sent through it in the other direction. In contrast it will block light of the opposite polarization.
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #51 on: 24/08/2023 04:16:38 »
Quote from: hamdani yusuf on 24/09/2022 13:05:36
In the next videos I will demonstrate that even specular reflections can produce non-trivial behaviors of light polarisation.
Here it is. This was recorded last year, but only finished editing recently.
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #52 on: 24/08/2023 16:24:52 »
Demonstrating circular polarization using 3D glasses.
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #53 on: 25/08/2023 08:52:27 »
The next video will demonstrate circular polarization using double 3D glasses.
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #54 on: 02/09/2023 03:37:33 »
I'd like to share a recently uploaded great video demonstrating polarization of light.

If we already have the correct concept of light, the results here should have been expected. Unexpected results come from false assumptions.
« Last Edit: 02/09/2023 03:41:14 by hamdani yusuf »
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Offline Bored chemist

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Re: How to demonstrate polarization of light?
« Reply #55 on: 02/09/2023 11:13:15 »
Quote from: hamdani yusuf on 02/09/2023 03:37:33
If we already have the correct concept of light, the results here should have been expected.
The outcome was what I expected.
The colour comes from this
https://en.wikipedia.org/wiki/Circular_dichroism
And the "side view" spirals are due to this
https://sciencedemonstrations.fas.harvard.edu/presentations/polarization-scattering
bearing in mind that light is path-reversible.

What "false assumptions" were you talking about?
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #56 on: 02/09/2023 13:11:17 »
Quote from: Bored chemist on 02/09/2023 11:13:15
Quote from: hamdani yusuf on 02/09/2023 03:37:33
If we already have the correct concept of light, the results here should have been expected.
The outcome was what I expected.
The colour comes from this
https://en.wikipedia.org/wiki/Circular_dichroism
And the "side view" spirals are due to this
https://sciencedemonstrations.fas.harvard.edu/presentations/polarization-scattering
bearing in mind that light is path-reversible.

What "false assumptions" were you talking about?
Have you watched the video?
Did you pay attention to the reaction of the host and the guest when discussing the results?
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Offline Bored chemist

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Re: How to demonstrate polarization of light?
« Reply #57 on: 02/09/2023 13:14:17 »
Quote from: hamdani yusuf on 02/09/2023 13:11:17
Did you pay attention to the reaction of the host and the guest when discussing the results?
Yes, I did.
It turns out that the guest didn't think about CD and polarisation by scattering.
Perhaps he would have if he  had been given longer to think about it.
Now, perhaps you might like to answer my question:
What "false assumptions" were you talking about?
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Offline hamdani yusuf (OP)

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Re: How to demonstrate polarization of light?
« Reply #58 on: 02/09/2023 13:54:48 »
Quote from: Bored chemist on 02/09/2023 13:14:17
It turns out that the guest didn't think about CD and polarisation by scattering.
I assume that you are referring to circular dichroism.
Quote
Circular dichroism (CD) is dichroism involving circularly polarized light, i.e., the differential absorption of left- and right-handed light.
https://en.m.wikipedia.org/wiki/Circular_dichroism
Don't you realize that the experiment in the video uses linearly polarized light, instead of circularly polarized light?

You are confused between Circular dichroism and circular birefringence.
Quote
Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials.
https://en.m.wikipedia.org/wiki/Optical_rotation
« Last Edit: 02/09/2023 13:58:06 by hamdani yusuf »
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Offline Bored chemist

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Re: How to demonstrate polarization of light?
« Reply #59 on: 02/09/2023 16:06:22 »
Quote from: hamdani yusuf on 02/09/2023 13:54:48
Don't you realize that the experiment in the video uses linearly polarized light, instead of circularly polarized light?
Yes, of course I realised that.
Quote from: hamdani yusuf on 02/09/2023 13:54:48
You are confused between Circular dichroism and circular birefringence.
That can't be right because circular birefringence does not, of itself explain the colours.

Actually, I got CD muddled with optical rotatory dispersion (ORD).
Sorry about that.
But the fact that I mislabelled the phenomenon doesn't mean that I was making the wrong assumption so...
Once again...

Quote from: Bored chemist on 02/09/2023 13:14:17
What "false assumptions" were you talking about?
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