[hamdani yusuf (OP)]

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.

[hamdani yusuf (OP)]

Investigation on Polarization of Light 2 : Diffuse Reflection and Fluorescence

Demonstrating the effect of diffuse reflection and fluorescence to polarized light.

[Bored chemist]

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.

[hamdani yusuf (OP)]

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.

[hamdani yusuf (OP)]

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.

[hamdani yusuf (OP)]

This video is quite new, but some explanations given here are misleading.

Can you spot the errors?

[Deecart]

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.

[hamdani yusuf (OP)]

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.

[Deecart]

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.

[hamdani yusuf (OP)]

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

[hamdani yusuf (OP)]

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.

[hamdani yusuf (OP)]

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.

[hamdani yusuf (OP)]

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.

[hamdani yusuf (OP)]

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.

[Deecart]

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)).

[hamdani yusuf (OP)]

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.

[hamdani yusuf (OP)]

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.

[hamdani yusuf (OP)]

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.

[hamdani yusuf (OP)]

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.

[hamdani yusuf (OP)]

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.