Naked Science Forum
On the Lighter Side => Science Experiments => Topic started by: hamdani yusuf on 26/08/2022 11:07:09
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Polarization of electromagnetic wave can be easily demonstrated using microwave and radio wave due to the macroscopic size of their wavelengths and the antennae. In this thread I'll show how to demonstrate the phenomenon using light.
Investigation on Polarization of Light 1 : Brewster's Angle
Demonstration of polarization of light using reflection by dielectric material.
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Investigation on Polarization of Light 2 : Diffuse Reflection and Fluorescence
Demonstrating the effect of diffuse reflection and fluorescence to polarized light.
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If you look at the sky through a polarised filter and rotate the filter you will see that scattered light is (at least partly) polarised.
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If you look at the sky through a polarised filter and rotate the filter you will see that scattered light is (at least partly) polarised.
This video demonstrates that clearly, although the explanation is still missing.
Here's the explanation.
Here's another good demonstration and explanation.
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Here's another interesting demonstration from the same youtuber.
DEMO: Plastic Wrap between Crossed Polarizers (Birefringence)
Here are some insights and spectral measurements on the colorful effects you see when you put plastic wrap between crossed polarizers.
This time the explanation is quite clear.
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This video is quite new, but some explanations given here are misleading.
Can you spot the errors?
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Can you spot the errors?
Not sure (i dont know light polarisation well), but i think that he show a light bulb and give the example of the some wave straight polarised. But he ommit to speak of the more useal wave we found in the case of some light bulb : The elliptic polarisation and the circular polarisation.
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Can you spot the errors?
Not sure (i dont know light polarisation well), but i think that he show a light bulb and give the example of the some wave straight polarised. But he ommit to speak of the more useal wave we found in the case of some light bulb : The elliptic polarisation and the circular polarisation.
Picket fence model is often used to explain the linear polarization of light phenomena. But a simple scrutiny shows that it's incompatible with observations. It's even useless in explaining circular polarization and reflection by polarizers.
I’ve been teaching microwave polarisation wrong! - A Level Physics
So it turns out the way I've been teaching microwave polarisation is wrong!! Well, it's not so much wrong, it's the fact that the 'picket fence' analogy for polarisation isn't what it first seems. Where the picket fence only allows vertically polarised light through, a corresponding polarising filter only allows horizontally polarised light through! Watch this video for more explanation.
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Ok i understand better.
So the (linear) vertical polarised electromagnetic wave hit (the input) the vertical fence and because it is made of aluminium the electrons of the aluminium fence go up and down the fence and the result is some random polarised wave at the output of the fence.
The wave do not pass trought the fence, it is absorbed by the fence and is re-emited.
On the contrary, if we have a horizontal fence with the same vertical polarised wave, the wave is absorbed too (i suppose), but because there are not so much electrons (?), the electrons will not produce the vertical electronic wave inside the aluminium able to conterbalance the vertical electric wave of the electromagnetic wave.
So the result will be some linear vertical polarised wave at the output.
To verify this hypothesis, we need at least to try the same experince with some fence with different (larger) aluminium bars.
There should be some progressive decreasing of the output power when the bar width increase.
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To verify this hypothesis, we need at least to try the same experince with some fence with different (larger) aluminium bars.
There should be some progressive decreasing of the output power when the bar width increase.
I've already done several experiments with microwave. Here are some of them, which is relevant for explaining polarization.
Here's the model I proposed. I'me not really sure if it's new, since it's based on how a dipole antenna work. Can we derive Huygen's principle from equations of antenna? Or can we derive equations of antenna from Huygen's principle?
Investigation on microwave 37 : blocking mechanism
Investigation on microwave 38: blocking mechanism explanation
Investigation on microwave 39: Blocking mechanism evidence
Here's an example how the model can be used to predict experimental results.
Polarization twister design.
Signal splitting.
Asymmetric twister/splitter
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Here are some earliest experiments I've done with microwave to understand polarization.
video#4 shows a phenomenon called linear polarization which is observed in microwave transmission. Up to this point we just go with standard experimental setup usually done in school kids' physics laboratory.
VIDEO#5 shows something rarely demonstrated in schools lab, which is reflection by microwave linear polarizer.
In video#6, Elliptical Polarization is demonstrated using linearly polarized transmitter, a linear polarizer, and a reflector. There is also another method which is commercially used, but here we use already available components whose characteristics are individually identifiable.
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This video#9 shows a linearly polarized microwave's axis can be rotated by a sparse metal grating. It can also be turned into an elliptically polarized microwave if another sparse metal grating is added after the first.
I think this one is still not widely known. But you can get a significant insight to better understand polarization of electromagnetic waves.
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Following videos show interaction of microwave with partial polarizer.
This video introduces a new type of apparatus to explore microwave optics. The partial polarizing filter passes through microwave oscillating perpendicular to its axis while only partially blocks/reflects microwave oscillating parallel to its axis.
This video demonstrates axis rotation by partial polarizer.
Here we tried to produce circularly polarized microwave by using two partial polarizers to generate phase shift in vertical axis while leaving horizontal axis undisturbed.
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Here is another video investigating the effect of twin polarizer.
It shows the effect of double polarizer when they are close to each other but are still separated electrically. The last part shows the polarisation of microwave coming out from the last polarizer.
The next video will show the effect of double polarizer when they are close to each other and electrically connected, so stay tuned.
And here are videos demonstrating conjoined twin polarizer
In the end of the experiment, it's shown that rotating the receiver can make the reading down to 0, which means that the microwave is linearly polarized instead of eliptical or circularly polarized.
Here are some conclusions from the experiments using twin polarizers :
- microwave passed through a polarizer is oriented perpendicular to the conductors in the polarizer. In other words, polarizers can rotate microwave orientation.
- Electric conductance between polarizer's conductors modifies how they react to incoming microwave.
- Those findings further reinforce our hypothesis that matters interact with microwave by generating reactionary wave which then interferes with original wave.
My experiments put tight constraints on any attempt to explain polarization of electromagnetic radiation including light.
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I've already done several experiments with microwave. Here are some of them, which is relevant for explaining polarization.
Very good !
This kind of video is very helpfull.
I will try to do some comments about the experiences in the videos, one by one, just after viewing them.
I will perhaps say things you talk about in the other videos but i think it is better to do the comments just after viewing them one by one so as to stay with the facts.
Investigation on microwave 37 : blocking mechanism
So lets start gently with the "first" (number 37 here) : "Blocking mechanism".
The test of transmitance or passing thru (we cant say at this point if the wave is passing thru or re-emited) of the plastic material :
First glance, this material act as if there is no effect on the wave.
But more precisely, and not sure if you noticed : The value show on the wave receptor vary slightly when you move the plastic sheet.
When the plastic sheet stay still, it act as if it would have no effect on "the transmission" (this is how we can call this part of the phenomenon regardless of the internal behavior of the elementary physical objects within the matter) of the wave.
But if you move the plastic sheet, and during the move only, you have less "transmission".
And from there you could eventualy test some type of moving, rotation, upward/downward, backward/forward with this kind of "neutral" material.
Now, let suppose the plastic material is "neutral"
Your result :
1. Spare continuous vertical grid 6mm horizontal gap : 30% "passing" (you use the word "passing" word and it is probably better than using like me the "transmission" word, but we mean the same).
2. Dense continuous vertical grid 3mm horizontal gap : 0% "passing" (you use the "spare" and "dense" word but i think that saying that is almost meaningless (they are not categories), the distance in mm is the only usefull value).
3. Dense continuous grid, 3mm horizontal gap 10/10 vertical gap : 2% "passing".
4. Additional : Almost Same as 3 (the vertical gap is not 10mm but 5mm, this is what is suppose because you have 20 gap instead of 10) but the copper grid has been replaced by aluminium sheet.
In this case we have around 90% "passing".
I see it is the experience is suggested in my previous post.
Some basic criticism (perhaps you could correct the video) :
You give the grid spacing in mm but you dont give the wavelength of the emiter.
You forget to say the type of the polarisation of the wave; saying it is linear is no sufficient, you need to say the direction : Here the polarisation is linear and vertical.
We dont know "the tolerance" of the measure : Per example if the wave is polarised with the angle 90, is some wave polarised with the angle 92 received (with some loss of power of course) too ?
Same with the emiter : Whats the gauss (i suppose) power value around the mean ? (The variance).
More advanced criticism.
We dont really know if the grids are connected together (this could have some incidence on the result if we talk about electron movement)
You changed the copper with the aluminium (different materials so perhaps different behaviour) and also they do no have the same thickness.
Copper wire should be presented nacked so to be sure the plasic around it cant interfer with the result.
It is not clear what "passing" mean : Perhaps effect of the the grid is the rotating of the polarisation by exactly some angle and if you rotate the receptor by the same angle you will get 100% "passing".
Same with the wave length, perhaps the grid only change the wave length without changing the polarisation and the receptor is not well suited to receive these waves.
Perhaps it change both (polarisation rotation and wave length).
Something you could do to investigate the "passing" more accuratly is to verify that when you rotate the receptor (using per example steps of 10 degrees so as the get out of the gauss curve... (or whatever is best suited with your material) and you note the power value, you end up with the same passing value ( you can do the curve interpolation so as to be able to do the integration (the sum)).
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I will try to do some comments about the experiences in the videos, one by one, just after viewing them.
I will perhaps say things you talk about in the other videos but i think it is better to do the comments just after viewing them one by one so as to stay with the facts.
Agreed.
But more precisely, and not sure if you noticed : The value show on the wave receptor vary slightly when you move the plastic sheet.
When the plastic sheet stay still, it act as if it would have no effect on "the transmission" (this is how we can call this part of the phenomenon regardless of the internal behavior of the elementary physical objects within the matter) of the wave.
But if you move the plastic sheet, and during the move only, you have less "transmission".
And from there you could eventualy test some type of moving, rotation, upward/downward, backward/forward with this kind of "neutral" material.
Good observation. That's why I said that it doesn't affect "significantly", compared to the effect of the conductors.
Now we know that the plastic movement does affect the transmittance of microwave. I think it's worth further exploration in the next videos. We would have to find some ways to amplify the effects to produce reliable, unambiguous, and hopefully quantitative results.
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2. Dense continuous vertical grid 3mm horizontal gap : 0% "passing" (you use the "spare" and "dense" word but i think that saying that is almost meaningless (they are not categories), the distance in mm is the only usefull value).
I used those words because the experiment is meant to emphasize the difference, where there are only two sets of gaps here.
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4. Additional : Almost Same as 3 (the vertical gap is not 10mm but 5mm, this is what is suppose because you have 20 gap instead of 10) but the copper grid has been replaced by aluminium sheet.
In this case we have around 90% "passing".
The purpose of this experiment is simply to show that opacity of an object is not just linearly correlated to the area coverage of the conductors. I didn't want to add more complexities beyond what's necessary to reach the goal. If you think there are some valuable information we can potentially get from such experimental variations, please let me know. I'll consider to do that.
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Some basic criticism (perhaps you could correct the video) :
You give the grid spacing in mm but you dont give the wavelength of the emiter.
You forget to say the type of the polarisation of the wave; saying it is linear is no sufficient, you need to say the direction : Here the polarisation is linear and vertical.
We dont know "the tolerance" of the measure : Per example if the wave is polarised with the angle 90, is some wave polarised with the angle 92 received (with some loss of power of course) too ?
Same with the emiter : Whats the gauss (i suppose) power value around the mean ? (The variance).
Those videos are part of a series compiled in a playlist named Investigation on Microwave Transceiver.
The specifications of the equipment are mentioned and shown in earlier videos. The newest video is #71. I don't want to waste much time explaining them over and over again. I can simply put them in video description.
You can see the whole video series in my other thread if you are interested.
https://www.thenakedscientists.com/forum/index.php?topic=66414.0
The intensity of the emitter may be stated in Watt/m?. But the experimental kit only enables us to make relative measurements. I don't have the tools to measure them in some standard units.
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We dont really know if the grids are connected together (this could have some incidence on the result if we talk about electron movement)
I also tested the grid with the conductors are connected at their ends. When those connectors are far from interacting area, they have no visible effect.
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Copper wire should be presented nacked so to be sure the plasic around it cant interfer with the result.
The effects of the plastic or rubber are not significant.
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It is not clear what "passing" mean : Perhaps effect of the the grid is the rotating of the polarisation by exactly some angle and if you rotate the receptor by the same angle you will get 100% "passing".
I addressed this concern in another video. But here, there is no rotation of polarization axis detected. Symmetric structure of the grid doesn't suggest that either.
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Same with the wave length, perhaps the grid only change the wave length without changing the polarisation and the receptor is not well suited to receive these waves.
It's very unlikely, considering that there would also be change of frequency. Superposition of waves with slightly different frequency would produce beat, which is unobserved here.
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The newest video is #71.
This video is also related to polarization, and how it's affected by reflection.
When editing the experiment with double reflector, I got an idea that diagonally polarized microwave can produce interesting results. I hope to share the new video with you soon. Stay tuned.
Here it is. I hope you enjoy it.
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But more precisely, and not sure if you noticed : The value show on the wave receptor vary slightly when you move the plastic sheet.
When the plastic sheet stay still, it act as if it would have no effect on "the transmission" (this is how we can call this part of the phenomenon regardless of the internal behavior of the elementary physical objects within the matter) of the wave.
But if you move the plastic sheet, and during the move only, you have less "transmission".
And from there you could eventualy test some type of moving, rotation, upward/downward, backward/forward with this kind of "neutral" material.
Good observation. That's why I said that it doesn't affect "significantly", compared to the effect of the conductors.
Now we know that the plastic movement does affect the transmittance of microwave. I think it's worth further exploration in the next videos. We would have to find some ways to amplify the effects to produce reliable, unambiguous, and hopefully quantitative results.
I've checked this out, and come to conclusion that the change of transmission is caused by diffraction and grazing reflection effects. When the edge of the plastic board is hit by microwave beam, some power of the beam is deflected to slightly different direction, reducing power of the beam going in straight direction.
I have uploaded new video showing diffraction in microwave frequency.
Basically, the experiment result leads us to conclude that diffraction comes from the material blocking the microwave path. When the obstruction is opaque enough, we find no diffraction. It's similar to my experiment using laser showing non-diffractive obstruction.
This result is not widely known yet.
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Ok.
I watched the videos.
Not simple to do some review for everyone of them because of the redundancy and the lack of some link between them..
So i finaly will try some other approach.
Here, what i have see is that you dont really do some experimentation everyone would agree with, but instead do some demonstration, using for your conclusion things you state they are right (because it is what you think it is what every scientist believe) This is very confusing for the viewer who dont master the physic of light.
Something that you should have done at first place :
Trying to understand how your emmiter/receiver apparatus is working, without any additional material.
This should be the basis of every further observation.
1. What is the constitution of the "wave" the emmiter produce.
Per example you are talking of "the wave" of the beam, and it is at this level of detail that all your reasoning is relying uppon.
But i am pretty sur there are many waves that constitute the beam.
So you have to start with some definition :
What is the wave.
What is the beam.
Where is the emmitter (the emmiter is not localised, it is a rod). Perhaps we could use something to have lower signal but more spacialy concentrated ?
Why do we have some rectangular plastic "tube" added to the emmiter and receiver ? (strange design..)
What is the dispersion of the beam ??? What is the dispersion of the photon ??? This is essential to understand all what follow.
This sort of fundamental questioning can help to avoid confusion between the wave representation everyone show (the electric and magnetic wave) advancing in space, and the real physical object.
When we see this kind of representation, we can be confused by the sinusoid representing the electrical wave ... a wave ??? (i know what a field is but a wave ...) and where it is placed into the space (majority of fields have a infinite action within space).
So before playing with the polarity i think you should clarify what "a wave" is (using experiments of course).
Other thing.
Some error in some video (i suppose i have see) is that if you turn the receiver, the value can change with no valid reason, due to the gravity... because the needle is impacted by gravity.
So you should avoid to turn the receiver (until you have some digital receiver), and turn the emitter instead.
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So you have to start with some definition :
What is the wave.
What is the beam.
This is how Google defines wave, with physics as context.
a periodic disturbance of the particles of a substance which may be propagated without net movement of the particles, such as in the passage of undulating motion, heat, or sound.
And the more specific context for electromagnetic wave.
a variation of an electromagnetic field in the propagation of light or other radiation through a medium or vacuum.
And this is how beam is defined.
a ray or shaft of light.
a directional flow of particles or radiation.
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Where is the emmitter (the emmiter is not localised, it is a rod). Perhaps we could use something to have lower signal but more spacialy concentrated ?
Basically this series of experiment is a sequel of previous experiments regarding diffraction of light, which leaves some unanswered questions. I hope from the next experiments we can build a workable model to explain the behavior of electromagnetic waves in general, and their interaction with matters.
video #1 : Introduction
In this video series we are going to investigate another form of electromagnetic wave, which is commonly called microwave. By doing so, hopefully we can get better understanding on the nature of electromagnetic wave.
A huge advantage of using microwave compared to visible light is its wavelength which is in the order of a few centimeters, which makes it convenient to manipulate. Variables obscured by the small scale of optical experiments can be easily observed and manipulated.
Why do we have some rectangular plastic "tube" added to the emmiter and receiver ? (strange design..)
Rectangular "tubes" are not made of plastic. They are made from metal, and act as directional antenna, which concentrate microwave beam to one narrow direction, hence the wave signal can still be measured for longer distance.
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This sort of fundamental questioning can help to avoid confusion between the wave representation everyone show (the electric and magnetic wave) advancing in space, and the real physical object.
When we see this kind of representation, we can be confused by the sinusoid representing the electrical wave ... a wave (i know what a field is but a wave ...) and where it is placed into the space (majority of fields have a infinite action within space).
So before playing with the polarity i think you should clarify what "a wave" is (using experiments of course).
I addressed more basic questions about electromagnetic wave in some other threads. This one is about demonstrations for polarization of light. I made the experiments especially for the cases where common explanations I found online don't seem to add up, thus need clarifications.
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So you have to start with some definition :
What is the wave.
What is the beam.
This is how Google defines wave, with physics as context.
a periodic disturbance of the particles of a substance which may be propagated without net movement of the particles, such as in the passage of undulating motion, heat, or sound.
And the more specific context for electromagnetic wave.
a variation of an electromagnetic field in the propagation of light or other radiation through a medium or vacuum.
And this is how beam is defined.
a ray or shaft of light.
a directional flow of particles or radiation.
Yes, but do you think this kind of mathematical "representation" is compatible with the experimentation you do ?
You infer in a spacialy way and you conclude using this mathematical representation (i dont say you are the only one doing this, so i suppose you already have conditioned thinking).
Perhaps to understand the problem it could be usefull to use the classical "representation" you showed at 1mn02 of this video :
Here, you show some spacialy representation of the "electric field".
Do you really think the figure show how the "field" occupy the 3D space ?
Do you really think the field stop at the value showed by the "arrow" of the field ?
Do you really think the field is limited at some plane ?
If you add the magnetic component of the wave, do you think the field is some monopole ?! (why nobody talk about the N and S of the magnetic field ?)
Do you think the field (result of the photons) cant be received at 100 km perpendicular of the moving independently of the wave length ? (This would be a nice discovery, so we could do the jedi lightsaber...)
What has the lateral espacement of the grid to do with the longitudinal wave length ?...
Etc.
Therefore, i think you should try to explain with "words" and reasoning what the wave "is", at first place (and dont just repeat wrong things you have heard already, so as to add some knowledge).
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Rectangular "tubes" are not made of plastic. They are made from metal, and act as directional antenna, which concentrate microwave beam to one narrow direction, hence the wave signal can still be measured for longer distance.
Thats bad, because this hinder logicaly some further investigation on the change of direction of the raw wave (you dont know what this initial change could have change on the raw wave)
Furthermore, to be sure to have some straight wave you should use some parabolic reflector like used with radars.
Like here : https://www.radartutorial.eu/06.antennas/Antenne%20parabolique.fr.html
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Thats bad, because this hinder logicaly some further investigation on the change of direction of the raw wave (you dont know what this initial change could have change on the raw wave)
The behaviour of microwave horns is well understood.
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The behaviour of microwave horns is well understood.
But surely the principle of doing experimentation is not well understood by anyone.
You can not demonstrate reliably any further phenomenon behaviour if your experimental devices itself use the phenomenon you want to study.
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Yes, but do you think this kind of mathematical "representation" is compatible with the experimentation you do ?
You infer in a spacialy way and you conclude using this mathematical representation (i dont say you are the only one doing this, so i suppose you already have conditioned thinking).
I don't think that I have to reinvent the wheel. So far, the model I used here haven't lead to contradiction. The experiments are needed to see how matters react to incoming electromagnetic radiation, by emitting reactionary wave. Those waves are then combined by superposition.
My model can be thought as an extention to the working principle of antenna, which can be shown clearly here.
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Human knowledge about electromagnetic waves is pretty much accurate, at least for some commonly used spectra. Here is some examples.
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You are still wrong and I think that it would be kind to the OP if a passing mod could split my forlorn attempts to educate you into a separate thread.
the thought had occurred to me, when I get a spare moment I’ll go through this.
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You are still wrong and I think that it would be kind to the OP if a passing mod could split my forlorn attempts to educate you into a separate thread.
the thought had occurred to me, when I get a spare moment I’ll go through this.
Thanks.
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Investigation on Polarization of Light 2 : Diffuse Reflection and Fluorescence
Demonstrating the effect of diffuse reflection and fluorescence to polarized light.
In the next videos I will demonstrate that even specular reflections can produce non-trivial behaviors of light polarisation.
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In the next videos I will demonstrate that even specular reflections can produce non-trivial behaviors of light polarisation.
For comparison, I consider the behavior of microwave polarization in the video below as trivial, although it may not be widely known to lay persons.
The newest video is #71.
This video is also related to polarization, and how it's affected by reflection.
When editing the experiment with double reflector, I got an idea that diagonally polarized microwave can produce interesting results. I hope to share the new video with you soon. Stay tuned.
Here it is. I hope you enjoy it.
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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)
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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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Sunglasses!
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Sunglasses!
Not all sunglasses are polarizing.
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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.
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If you want to compare various types of 3d glasses, just watch this video.
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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?
5018 Views
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Here's one clue for one of the errors.
https://en.wikipedia.org/wiki/Polarizer#Absorptive_polarizers
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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There's one comment on the YouTube video which I think more people should know.
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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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?
5018 Views
In 1:40, he only explain the need for linear polarization. The comment I quoted above explains why circular polarizer is needed.
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Here's one clue for one of the errors.
https://en.wikipedia.org/wiki/Polarizer#Absorptive_polarizers
A Polaroid polarizing filter functions similarly on an atomic scale to the wire-grid polarizer. ...
https://en.wikipedia.org/wiki/Polarizer#Wire-grid_polarizers
(https://upload.wikimedia.org/wikipedia/commons/thumb/9/94/Wire-grid-polarizer.svg/680px-Wire-grid-polarizer.svg.png)
This is contrary to the diagram shown in the video at 2:33.
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This is how circular polarizers work.
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
(https://upload.wikimedia.org/wikipedia/commons/thumb/8/84/Circular.Polarization.Circularly.Polarized.Light_Circular.Polarizer_Creating.Left.Handed.Helix.View.svg/990px-Circular.Polarization.Circularly.Polarized.Light_Circular.Polarizer_Creating.Left.Handed.Helix.View.svg.png)
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
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.
(https://upload.wikimedia.org/wikipedia/commons/thumb/8/82/Circular.Polarization.Circularly.Polarized.Light_Circular.Polarizer_Passing.Left.Handed.Helix.View.svg/990px-Circular.Polarization.Circularly.Polarized.Light_Circular.Polarizer_Passing.Left.Handed.Helix.View.svg.png)
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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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Demonstrating circular polarization using 3D glasses.
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The next video will demonstrate circular polarization using double 3D glasses.
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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.
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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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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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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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It turns out that the guest didn't think about CD and polarisation by scattering.
I assume that you are referring to circular dichroism.
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.
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
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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.
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...
What "false assumptions" were you talking about?
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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.
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...
What "false assumptions" were you talking about?
I must admit that you have an extraordinary confidence I've rarely seen before.
Steve Mould seemed to assume that optical rotation isn't affected by light frequency when he was asked to predict the result. Your reply indicates that you've made the same assumption.
The host seemed to expect that the results weren't widely known yet. Otherwise, he wouldn't ask about it in the first place.
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Your reply indicates that you've made the same assumption.
No.
My reply says that optical rotation is affected by wavelength.
That's what ORD is.
Try reading what I said a few times.
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The host seemed to expect that the results weren't widely known yet.
I have textbooks from the 1930s which make it clear that the phenomenon was well known then.
A guy on YT didn't know about it; so what?
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Steve Mould seemed to assume that optical rotation isn't affected by light frequency
Here's a picture of two clips from that video. They both show pictures from Steve Mould's video.
In it, you can clearly see the different colours you get at different angles.
And yet you say that he didn't expect to see different colours.
Your assertion is absurd.
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Once again...
Quote from: Bored chemist on Today at 13:14:17
What "false assumptions" were you talking about?
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Here's the second video.
I pointed in the comments section about a problem with the explanation at 4:30. It says that receiving particle is accelerated perpendicular to the acceleration of the transmitting particle. But experiments with dipole antennas show that they are parallel to each other.
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Here's a picture of two clips from that video. They both show pictures from Steve Mould's video.
In it, you can clearly see the different colours you get at different angles.
And yet you say that he didn't expect to see different colours.
Your assertion is absurd.
In 3B1B's video, Steve was asked to predict the result, and he literally said nothing will happen. It's not my assertion. By saying that, he made some implicit assumptions which he wasn't aware of due to time constraints to think about it more thoroughly.
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Once again...
Quote from: Bored chemist on Today at 13:14:17
What "false assumptions" were you talking about?
I've answered that. You're free to accept it or not.
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Your reply indicates that you've made the same assumption.
No.
My reply says that optical rotation is affected by wavelength.
That's what ORD is.
Try reading what I said a few times.
Which part of this says that?
That can't be right because circular birefringence does not, of itself explain the colours.
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The next video will demonstrate circular polarization using double 3D glasses.
Here it is. I hope you enjoy it.
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In 3B1B's video, Steve was asked to predict the result, and he literally said nothing will happen.
And I explained why.
Perhaps he would have if he had been given longer to think about it.
Circular birefringence says that a sugar solution will rotate the plane of polarised light.
It does not say anything about colours, does it?
So, when I said " circular birefringence does not, of itself explain the colours." I was right, wasn't I.
ORD does explain the colours.
The polarisation by scattering explains why you do not need an analysing filter to see themhe made some implicit assumptions which he wasn't aware of
He was aware of the facts.
He even made a very good video about them.
You seem to be muddling up two things
Not knowing about something and
not realising, at short notice, that something you know is applicable here.
He didn't make the wrong assumption. He just didn't think his deduction through properly.
So, once again...
Quote from: Bored chemist on Yesterday at 13:14:17
What "false assumptions" were you talking about?
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Unexpected results come from false assumptions.
You seem to mean "If you don't give people time to think about something properly, they may make a mistake."
That's not surprising.
It's also nothing to do with physics.
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I pointed in the comments section about a problem with the explanation at 4:30. It says that receiving particle is accelerated perpendicular to the acceleration of the transmitting particle. But experiments with dipole antennas show that they are parallel to each other.
For what it's worth, I think you are right.
But I don't think it matters much.
At about 07:15 he gets it right.
So, you can't say "He is making a false assumption", But you can say he messed up when writing his script.
Congratulations! you proved he's human.
Quote from: hamdani yusuf on Yesterday at 13:54:48
Don't you realize that the experiment in the video uses linearly polarized light, instead of circularly polarized light?
And at 18:30 to 19:00 or so, the video explains why your objection was irrelevant.
I already knew that.
Did you?
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For what it's worth, I think you are right.
But I don't think it matters much.
At about 07:15 he gets it right.
So, you can't say "He is making a false assumption", But you can say he messed up when writing his script.
Congratulations! you proved he's human.
If a mistake is not addressed, then there is risk that it will be repeated. Someone who learns from the video might get unnecessarily confused, and subsequently make bigger or further mistakes.
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Here's another simple way to demonstrate the polarization of light using every day objects.
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I've recorded a video showing behavior of absorptive polarizer in visible light. It's in contrast to reflective polarizer I've shown using metal grids in microwave spectrum.
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Searching for reflective polarizer, I found this video.
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Searching for absorptive polarizer in YouTube doesn't give informative videos, but Google gives some sources. Some of them equate it to dichroic polarizer. So, I searched it in YouTube and get some results.
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Other results from the searching only give theoretical explanation without physical demonstration.
Although this one is pretty good.
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Polarizer ? How it Works: Visible Light Linear Polarizers
METHODS OF PRODUCING LINEAR POLARIZED LIGHT:
There are numerous ways of developing linearly polarized light. There are three widely known mechanisms:
Double refraction or birefringence
Reflection
Dichroism
...
DICHROIC ABSORPTIVE POLARIZERS
API?s and most commercially produced polarizers are dichroic polarizers. They exhibit dichroism; the property of absorbing light that is polarized in a particular direction. A dichroic linear polarizer can be considered as having an indicated absorption and transmission axis. The transmission axis is also referred to as the ?polarizing axis.? Stretched Polyvinyl Alcohol (PVA) is most commonly used in dichroic polarizers.
https://www.apioptics.com/about-api/resources/visible-light-linear-polarizer/
This is one of the results in Google search.
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In Wikipedia article, reflective polarizer is called beam-splitting polarizer.
Linear polarizers can be divided into two general categories: absorptive polarizers, where the unwanted polarization states are absorbed by the device, and beam-splitting polarizers, where the unpolarized beam is split into two beams with opposite polarization states.
https://en.m.wikipedia.org/wiki/Polarizer
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This demonstration of polarization rotation by polarizer should be enough to explain and demistify what's so called three polarizers paradox.
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three polarizers paradox.
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I've recorded a video showing behavior of absorptive polarizer in visible light.
Here it is.
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three polarizers paradox.
It's not really a paradox.
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three polarizers paradox.
It's not really a paradox.
A paradox is a logically self-contradictory statement or a statement that runs contrary to one's expectation.
There are someone clearly expected different results, otherwise they won't call it weirdweird, creepy, or counterintuitive.
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He suggests near the end of the video, calling the polarizer filter may lead people to expect different results.
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I just got an even stronger evidence that diffracted light is produced by the edges of the obstacle, instead of the space between those edges. The experiment involves linear polarization.
I've finally uploaded the video.
In a previous video from my other thread, the edges of polarizers are used to produce diffraction pattern. From the results, we can cross-check our current model on how light interacts with matter.
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A paradox is a logically self-contradictory statement or a statement that runs contrary to one's expectation.
Correct and it is not logically self-contradictory to have light show through when a polarizer is at 45 deg between two polarizers at 90 deg to each other. You get exactly what is expected if you have any knowledge about quantum physics.
A boat that is made out of steel is not a paradox if you understand buoyancy even though steel sinks.
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For what it's worth, the classical description of polarisation also explains the transmission through three polarisers.
It's not a very paradoxical paradox.
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For what it's worth, the classical description of polarisation also explains the transmission through three polarisers.
It's not a very paradoxical paradox.
I agree. The article below explains how it's explained classically, and identifies the cause of confusions.
http://alienryderflex.com/polarizer/
Third-Polarizing-Filter Experiment Demystified ? How It Works
Spookiness and the Word ?Filter?
Why do these results seem spooky? The reason is because of the misapplication of the word ?filter.? A filter is commonly understood to mean a device that knocks some items out of a stream, while leaving others essentially untouched. A good example of a filter is a sieve ? it blocks objects of a particular size, while allowing objects of other sizes to pass through.
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=85375.0;attach=34165;image)
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=85375.0;attach=34167;image)
Understood this way, the results of the polarizer experiment are indeed spooky. If the all-blocking equivalent of Figure 2 is constructed using sieves or color frequency filters (see Figures 4 and 5), we are certainly confident that the addition of more filters in the middle of the sequence will not yield different results at the end.
But what if our so-called ?filters? could not only block components of the stream, but also change them? Then we would not be surprised at all if the addition of new ?filters? in the middle caused items to get through to the end. If a sieve could not only block particles, but also change their size, or if a color filter could not only block frequencies, but shift light to a different frequency, then all bets are off.
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In my other thread on microwave transmission, I've shown some effects of polarization which have similarities with the effects in visible light spectrum. But I haven't found the analogue of conjoined twin polarizer.
Here is another video investigating the effect of twin polarizer.
It shows the effect of double polarizer when they are close to each other but are still separated electrically. The last part shows the polarisation of microwave coming out from the last polarizer.
The next video will show the effect of double polarizer when they are close to each other and electrically connected, so stay tuned.
And here are videos demonstrating conjoined twin polarizer
In the end of the experiment, it's shown that rotating the receiver can make the reading down to 0, which means that the microwave is linearly polarized instead of eliptical or circularly polarized.
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Light Interference versus Polarization
In this demonstration, a Michelson-Morley Interferometer is used to create an interference pattern between a beam of light with itself. This interference seems to be abolished when one ray's polarization is rotated by 90 degrees.
This video can save me money, time and effort to demistify experimental results with light.