Talk:Circular polarization

Citation:

Circular (and eliptical) polarization is possible because the propagating electric (and magnetic) fields can have two orthogonal components with independent amplitudes and phases (and the same frequency).

I would understand circular polarisation if E and M fields could have different frequencies. But with same frequencies, as stated here, I don't see why there should be circular polarization. Thanks, --Abdull 20:51, 4 Apr 2005 (UTC)

This article, and the related polarization article, have drifted a bit. The essential insight needed to understand all polarization phenomena is that the transverse wave is two-dimensional. The usual example of a water wave is confusing in this respect, because it is not; the water wave motion occurs only perpendicular to the water surface. Only the special case of linear polarization behaves like water waves. The electric field of a plane, two dimensional electromagnetic wave can be resolved into two orthogonal components, because, unlike a water wave, the wave "motion" is two-dimensional. Each of these components can have an independent phase and an amplitude. The question above demonstrates the need to emphasize the essential two-dimensional nature of the electromagnetic wave early in the article. I hope this helps.

AJim 03:54, 12 July 2007 (UTC)

direction of helices

Citation: "When looking toward the source, right hand circular polarized light rotates clockwise as time increases, and describes a right hand helix along the propagation axis."

Logic dictates that exactly one of these two statements is correct: (1) "When looking toward the source, right-hand circular polarized light rotates clockwise as time increases." (2) "[P]olarized light […] describes a right-hand helix along the propagation axis."

Anyone know which is true and which needs to be corrected?

direction of helices (2)

I agree with the inconsistency in the article.

the probelm is to differ between circular polarization helicity and handedness

Let's take light that describes a clockwise rotation along its direction:

• it has positive helicity.
• it is right-handed
• but left circular polarized, as the definition for circular polarisation comes from the "classic" spectroscopists who defined by looking into the beam /at the source, and not along the beam.

see: http://courses.washington.edu/phys55x/Physics%20557_lec9_App.htm

circularly polarizing materials

Now that this has a publicly accessible manifestation, in 3D movies such as Real D, could we have something more about the practicalities, circularly polarizing materials and Liquid Crystal filters for circular polarization, or at least links to articles about them? (I was intrigued that the left and right lenses of my briefly hired 3D glasses seemed to have different effects on colour filters in the theatre, and on my cellphone display. More about that would be interesting -- Hugh7 (talk) 08:34, 24 December 2007 (UTC)

I wrote something about "The classical way to produce circular polarization ..." here: Talk:Polarization#Photographic_Polarizers (at the current end of that section). Maybe we need to put that somewhere "official". In particular, it is important to know that reversing the direction light goes through a circular polarizer makes it a linear polarizer. --AJim (talk) 21:14, 19 March 2009 (UTC)

FM Radio

About this paragraph:

The term "circular polarization" is often used erroneously to describe mixed polarity signals used mostly in FM radio (87.5 to 108.0 MHz), where a vertical and a horizontal component are propagated simultaneously by a single or a combined array. This has the effect of producing greater penetration into buildings and difficult reception areas than a signal with just one plane of polarization. This would be an instance where the polarization would more appropriately be called random polarization (or simply unpolarized). See Stokes parameters.

If I understand correctly, an ordinary dipole antenna will radiate a linearly polarized wave. If there is a second radiating dipole nearby (a simple "array"), polarization of the wave seen at a distance from the antenna will depend on both the relative orientation of the second dipole and the relative phase of the signals driving the two dipoles (phasing is affected by feed line length differences, among other factors). In any case, if the two signals have a relative phase other than 0 or pi, the wave will necessarily be elliptically polarized, with circular polarization as a special case if the relative phase and amplitudes are just right. As long as the antennas do not move, I think the polarization state, for a line-of-sight signal, in any particular direction, will be stable and well defined as well and should not be called unpolarized.

--AJim (talk) 20:48, 19 March 2009 (UTC)

My understanding is that "mixed polarization" as described above is not allowed by the FCC -- only either Horizontal, Circular or Elliptical. Slant polarization, with H and V at different powers but in phase, is not allowed for FM or TV. See: CFR 47 § 73.316. I believe the entire paragraph should be removed.

-- algocu (talk) 18:51, 10 September 2012 (UTC)

Since the immediately above note showed up on my user talk page as well as here, I will respond. My comment was directed to the idea that such a signal should not be called "unpolarized"; my interest is simply theoretical. Whether the FCC allows it is something else, but I agree it would be relevant in the context of that paragraph. If there are in-phase V and H components then I think the result is necessarily linear polarization in some plane, which might not be H or V (slant), and, for all I know, would not be allowed. If the components are not in phase there will be elliptical polarization of some sort, possibly circular, which might be allowed apparently. Incidentally, I remember hearing that circular polarization is used in some services not because of better penetration but because handedness reverses after reflection and thus a circularly polarized receiving antenna can achieve some immunity to multi-path distortion.

--AJim (talk) 20:05, 10 September 2012 (UTC)

complaints

The article needs to be more concise! —Preceding unsigned comment added by 96.248.168.165 (talk) 22:45, 6 April 2009 (UTC)

The article is too concise! I've been looking for a simple explanation of the "mechanics" of a circular-polarizing optical filter, and can't find it anywhere. WilliamSommerwerck (talk) 20:05, 19 May 2009 (UTC)

What do you mean by "mechanics"? Are you asking, "how do you make a filter that produces circularly polarized light"? --AJim (talk) 01:54, 20 May 2009 (UTC)

This article is absurdly long! Consider a rewrite using say Jackson, Griffiths, and maybe Lorrain and Corson as references. — Preceding unsigned comment added by 169.231.35.236 (talk) 03:08, 18 September 2011 (UTC)

meaning of variable z in mathematical description section

In this equation

$\mathbf {E} (\mathbf {r} ,t)=\mid \mathbf {E} \mid \mathrm {Re} \left\{|\psi \rangle \exp \left[i\left(kz-\omega t\right)\right]\right\}$

I see the variable r on the left side, but I see z on the right in the exponent and I do not know how these two variables are related. The variable z is not defined. Please forgive my ignorance if this should be obvious. However, if I need help, perhaps there are some other readers who will too. I do understand the significance of t as time, although I think it, and r should be defined also.

$\mathbf {B} (\mathbf {r} ,t)={\hat {\mathbf {z} }}\times \mathbf {E} (\mathbf {r} ,t)$

My same question applies to the : ${\hat {\mathbf {z} }}$ in the second equation. How is it related to r? --AJim (talk) 01:11, 13 May 2009 (UTC)

I agree with AJim, this article is very sloppy with definitions of mathematical symbols. Achoo5000 (talk) 04:58, 4 November 2009 (UTC)

Well it's a physics article so now wonder it's sloppy about mathematical definitions ;)

z usually denotes the displacement, whereas r denotes the current coordinates (or in the case of e.g. E(r,t) the space dependency just as t is the time dependency). ẑ then simply indicates the unit vector in the direction of the displacement.

I hope that's somewhat correct, I only skipped across the formulas (afterall I'm just an experimental physicist ;) ) Isron (talk) —Preceding undated comment added 09:52, 10 March 2010 (UTC).

Left handed verses right handed clarification

(The below section is lengthy and out of date, initially deleted by the co-Author, but then returned after discovering that doing so was bad form)

In the hope of putting an end to the right handed left handed confusion I have made the following changes in the text. I have included a description of the changes in these talk pages because of the importance of the issue.
Before

In physics, astronomy, and optics, polarization is defined as seen from the receiver, such as a telescope or radio telescope. By this definition, if you could stop time and look at the electric field along the beam, it would trace a helix which is the same shape as the same-handed screw. For example, right circular polarization produces a right-threaded (or forward-threaded) screw.

After

In physics, astronomy, and optics, polarization is defined as seen from the receiver, such as a telescope or radio telescope. By this definition, if you could stop time and look at the electric field along the beam, it would trace a helix which is the same shape as the same-handed screw. For example, as indicated in the diagram to the right, right circular polarization produces a right-threaded (or forward-threaded) screw, where the thumb of the right hand or the point of a right handed screw points away from the receiver. Using this same convention, this polarization is also referred to as clockwise because the electric field rotates in the clockwise direction from the point of view of the receiver.

I have also added the following subheading to the image on the right.

Right-handed/Clockwise circularly polarized light as seen from the receiver.
This is the convention used in physics, astronomy, and optics.

Although I have merely expanded what is already here, it would be helpful if others confirmed the accuracy of these changes.
Dave 2346 (talk) 01:26, 3 January 2010 (UTC)

I think you are mistaken. In physics, when considering handedness of a wave, the thumb points in the direction of propagation, not against it. Note also that if you turn a right-handed screw around (rotate it 180°), it remains a right-handed screw. It does not suddenly become a left-handed one. I think the discrepancy arises between whether one considers the shape of the helix at a fixed moment in time, or whether one considers the time evolution of the field vector in a plane perpendicular to the direction of propagation.

Given the apparent uncertainty among editors here, this section clearly requires citations to reliable sources to establish what definitions are correct in each field. I will remove some material and mark the rest cite-needed. By the way, Federal Standard 1037C does not clearly say what the article claims. It says "Circular polarization may be referred to as "right-hand" or "left-hand," depending on whether the helix describes the thread of a right-hand or left-hand screw, respectively."--Srleffler (talk) 07:16, 3 January 2010 (UTC)

As far as I can recall (and this should be checked in a reliable source), in physics one considers the evolution of the field vectors in a fixed plane (such as the plane of the receiver). The thumb points in the direction of propagation, while the fingers point in the direction the field vectors rotate in time. If one considers the helix formed by the tips of the field vectors at a single instant of time, a "right handed" wave according to this definition will have a helix that resembles the thread of a left-handed screw. I think the claim in the article that the physics definition matches the thread of a screw is simply wrong, but rather that this is true of the engineering definition. If I am right, then the figure is actually a left-handed wave using the physics definition, and the claim that Federal Standard 1037C uses the engineering definition is correct. If I am mistaken, then the claim about FS-1037C is simply wrong; the article as written does not agree with that source.--Srleffler (talk) 07:41, 3 JanuaryAuthor, Jan 15th 2010 (UTC)

Left handed verses right handed clarification Continued.

The images in the "General Description" section appear to be incorrect. Their captions should be switched. The animations of the handedness appear correct, but they are opposite of these incorrectly captioned images when you compare the helixes. — Preceding unsigned comment added by 2601:285:8200:64F0:89A2:58FF:DB15:44C1 (talk) 21:34, 11 December 2022 (UTC)

Srleffler, I think I've got it cornered.

It would seem with optics and physics that you point your thumb in the opposite direction of travel.
I came across this book.

HANDBOOK OPTICS Volume I,Devices , Measurements and Properties,Michael Bass
http://heartfeltemotion.com/Handbook_of_optics_second%20edition_Vol_1_Bass_M.pdf

It says in a footnote on page 272

Right-circularly polarized light is defined as a clockwise rotation of the electric vector when the observer is looking against the direction the wave is traveling .

In volume 2 we have a mathematical example..

HANDBOOK OPTICS Volume II,Devices , Measurements and Properties,Michael Bass
http://heartfeltemotion.com/Handbook_of_Optics_2_edition_vol2_Bass_M.pdf
Page 469 Equ (49) Quote:

In terms of the original stationary x , y axes , the optical field components at the output are
Eox = Ei (Constant) cos ω t - (Not important)
Eoy = Ei (Constant) sin ω t - (Not important)

The first terms in Eox and Eoy represent left circular polarization at the original optical frequency ω

With regards to Engineering.

In the book
Electromagnetic Waves & Antennas – S. J. Orfanidis.pdf
http://heartfeltemotion.com/Electromagnetic_Waves_and_Antennas_S._J._Orfanidis.pdf

Start reading 3/4 of the way down on page 44 and he talks in detail

Thus, the tip of the electric field vector rotates counterclockwise on the xy-plane. To decide whether this represents right or left circular polarization, we use the IEEE convention, which is as follows.Curl the fingers of your left and right hands into a fist and point both thumbs towards the direction of propagation. If the fingers of your right (left) hand are curling in the direction of rotation of the electric field, then the polarization is right (left) polarized.†

The footnote reads

†Most engineering texts use the IEEE convention and most physics texts, the opposite convention.

Are you in agreement that the Federal Standard 1037C adopts the convention of the physicists and the IEEE goes the way of the engineers?

Although this will be my first major edit I am going to see if I can make all this clear to the reader. By all means give me your feedback.
Dave 2346 (talk) 02:48, 5 January 2010 (UTC)

Left handed verses right handed clarification Continued. - Still inconsistent

This article seems to still be incorrect and inconsistent(?).

As stated correctly (I believe) under "direction of helices (2)"

Let's take light that describes a clockwise rotation along its direction:

* it has positive helicity. * it is right-handed * but left circular polarized, as the definition for circular polarisation comes from the "classic" spectroscopists who defined by looking into the beam /at the source, and not along the beam.

makes the following figure text inconsistent:

Right-handed/Clockwise circularly polarized Light (as seen from the receiver)

and the text:

It is also considered clockwise circularly polarized because for a receiver observing the wave approaching, the field rotates in the clockwise direction as it passes a given point in space.

The figure shows a wave that following its direction:

has positive helicity is right-handed has clockwise rotation

but seen from the receiver has counter clockwise rotation and what may be defined as left handed circularly polarized light.

Following parts are also inconsistent:

In this case the handedness of the helix does not match the defined handedness of the wave.

and

When determining if the wave is clockwise or counter-clockwise circularly polarized, one takes the point of view of the transmitter, and while looking in the same direction which the wave is propagating, observes the direction of the temporal rotation of the field.

To me this entire section is a bit hard to understand, would be nice if it was rewritten. For example i don't understand the concept of:

If one freezes the wave in time, the handedness of the screw type nature of the field, matches the defined handedness of polarization.

How does "freezing the wave in time" illustrate a movement path? I get really confused when reading this section, I hope im not the only one.

12:16, 23 March 2010 (UTC) —Preceding unsigned comment added by 194.71.85.66 (talk)

As it happens I am working on a new section for this page that will have lots of illustrations. Be sure to put the page on your watch list as it will be changing significantly in the next few days. At that time I would very much appreciate your feedback just as you have given it here.

Later I will be including a table in the section you are talking about which might help clear things up. I'll take another look at the text to see if it is misleading or contradictory as you say.<br)

In the mean time here is one of the images I've created and will be adding, it is an animation of right hand clockwise polarized light,(As defined by the receiver) http://commons.wikimedia.org/wiki/File:Cxircularly.Pxolarized.Lxight_Rxight.Hxanded.Axnimation.305x190.255Colors.gif .Point your right thumb toward the source and curl your fingers.

We thank you for your time.

Dave3 (talk) 20:11, 24 March 2010 (UTC)

Hello everyone!

I believe that what is described now in the article as the accepted convention about right- and left-handed polarization in physics is incorrect.

I read the discussion and I think that Srleffler's surmise (03 Jan 2010) about the physics convention is correct (i.e. point thumb in direction of propagation). According to RP Feynman's lectures (Vol. 1, ch.33-1) this is the convention used in physics. There might be different conventions in optics.

Greetings! (Nov 12th 2010) —Preceding unsigned comment added by 193.190.253.147 (talk) 13:40, 12 November 2010 (UTC)

I just checked and you are right. Here is the quote.

Feynman's lectures (Vol. 1, ch.33-1)

If the end of the electric vector, when we look at it as the light comes straight toward us, goes around in a counterclockwise direction, we call it right-hand circular polarization. ... Our convention for labeling left-hand and right-hand circular polarization is consistent with that which is used today for all the other particles in physics which exhibit polarization (e.g., electrons). However, in some books on optics the opposite conventions are used, so one must be careful.

In light of this I’m thinking that maybe we should just call the “In physics, astronomy, and optics” convention just the “First convention” and the second convention, the “Second convention” and then at the end explain in more detail what a mess the whole convention thing is in. At least that way we will not be misleading people.

If the there are no objections I will begin working on this. Dave3457 (talk) 04:09, 13 November 2010 (UTC)

Creation of a new first section...,General description

I reworked the introductory sentence because of the creation of a new first section, General description. No information was lost, it was worked into the new section.
The images are the appropriate size for my computer screen resolution of 1280x800 but are 25% wider for those using a resolution of 1024x768 but it doesn't seem to be too bad. The images are also somewhat distorted using that resolution. I don't know the percentage of people using each resolution but I don't know how it could be avoided anyway. I've read the thumbnail help section but if you know of a way to overcome this issue please let me know. Dave3457 (talk) 04:15, 14 April 2010 (UTC)

British spelling of circular polarization

I removed the bracketed note about the British spelling of polarization which read “In electrodynamics, circular polarization (also circular polarisation) of electromagnetic radiation is a polarization such that ….” Instead I just included a reference. I don’t know about anyone else but I can’t help but feel the bracketed note is a major distraction for the reader in a sentence that is very important and is all ready very concentrated with more important information. It doesn’t help that the spellings are so close and an “s” looks a lot like a “z”. I know personally that when I first read it, it completely threw me off. The alternative British spelling of polarization is already noted in the first sentence of the Polarization article and I’m not sure that isn’t enough. Ruining the flow of such an important sentence seems to be a very high price to pay for such a thing and doesn’t serve the British people any more than anyone else given its distractive nature.
The ratio of Google hits between "circular polarization" and "circular polarisation" is 5:1 and so it can be argued that it should mentioned more prominently, however I don’t believe such a high price has to be paid. It could be argued that more than a footnote is in order to warn people who are using search engines to research the subject, however, again, I think the first sentence is jammed with enough information as it is. Dave3457 (talk) 04:15, 14 April 2010 (UTC)

Added animations in Handedness section

While I added 3 animations just now, 2 are identical and so only 2 will be downloaded from the server by the surfer. Each are 290Kb and have been optimized. I tried to keep their size below 300Kb which is the size of the animation in the GIF animation article. If there are excessive delays in downloading the page, the left-handed animation can be removed if it really needs to be. Dave3457 (talk) 04:15, 14 April 2010 (UTC)

Corrected $\psi _{L}$ and $\psi _{R}$ Definitions

The formula for $\psi _{L}$ and $\psi _{R}$ were clearly wrong as they were completely independent of the relative phase between the x and y components. All that was shown was a global phase $\exp \left(\alpha _{x}\right)$ which can be ignored as it is present in both.

If you compute $\langle L|\Psi \rangle$ and $\langle R|\Psi \rangle$ you get the correct expressions. —Preceding unsigned comment added by 155.198.206.131 (talk) 11:06, 23 April 2010 (UTC)

Bra-ket notation unnecessary?

It seems that section Circular_polarization#Mathematical_description is using bra-ket notation -- anyone against simplifying it using undergraduate-level vectors and matrices notation? Thanks. Fgnievinski (talk) 03:13, 1 June 2010 (UTC)

That would seem very appropriate. If you do change it, may I suggest that you might think about placing what is already there into a separate, possibly hidden, section titled “Mathematical Description using Bra-ket notation” or something like that. Someone obviously spent quite a bit of time putting it together and it may be of use to those familiar with the notation. Note that in quantum mechanics circular polarization is mathematically interpreted as the spin of the photon. That’s most certainly the reason for the Bra-ket notation. In fact it would be great if someone included something to that effect on this page. Everything I know about it is pretty much summed up in this quote….I’ve cut and pasted the quote here for myself, yours or anyone else’s reference. Introduction_to_Quantum_Theory_2ED_David_Park_Sec_2.2_Pg32
Dave3457 (talk) 21:35, 30 June 2010 (UTC)

I understand where you guys are coming from, especially in the sense of actual application of the physics to real life "macroscopic" electronics (eg building antennas, measuring power delivered through EMI to a circuit, etc.). However, understanding the physics from a purely theoeretical and "self-consistent" point of view.... where all you care about is the way to create a circularly polarized photon and not its interaction with a conductive boundary or chiral polarizer.... is easier with Bra-Ket/Dirac. This is one of the great things about this notation: its graphically/notationally simple. its symmetry and lack of messy notation and symbols helps to keep your mind focused. You don't need to worry about whether or not you must perform a convolution over a complex domain, or a messy integral equation. Instead, you implicitly assume things about inner products, actions of operators, changes of basis, outer products, etc. that do not require as much thought. I always appreciate straightforward R3 representations when I need to imagine something that is interacting with a real system. But if I am concerning myself with a hypothetical particle, atom, photon, molecule, etc. that is floating in space somewhere, Dirac Notation is the way to go.184.189.220.114 (talk) 20:03, 8 March 2013 (UTC)

Fgnievinski’s Recent Changes

I noticed you’ve been putting time into the page. I’ve liked most of your changes. Some months ago I created the “General description” article/images and also tried, like you, to make the Handedness section more comprehensible. At first, for aesthetic purposes, I liked your idea of putting the left-handed images on the left side of page. I’m assuming you did it because edit links where bunching up on your screen or something. However, whatever we do I feel both images need to be on the same side of the page. That way people can more easily compare the left-handed polarization images to the right-handed polarization images. In my view practicality has to override aesthetics in this case.

Unless you object I’m going to move your quotes of the IEEE convention into the appropriate reference at the bottom of the page. I do not see the need to put the reader through the trouble of deciphering those sentences as they do not convey any new information and can only serve to confuse the reader. What is your take? Dave3457 (talk) 21:43, 30 June 2010 (UTC)

Hi Dave. Sorry, didn't see your msg before. Thanks for asking, but I guess the best way to catch one's attention is to edit it -- I'm all for Wikipedia:BOLD,_revert,_discuss_cycle! ;-) Thanks for your time. Fgnievinski (talk) 16:12, 2 July 2010 (UTC)

Ok, thanks for the link. I guess your a more aggressive personality then myself :) I do agree I could afford to be more bold, but the BRD page itself does say it should be a fall back. Dave3457 (talk) 18:08, 2 July 2010 (UTC)

Size of images in General Description section.

Fgnievinski, I noticed you reduced the pixel width from 485px to 400px. For people with a screen resolution of 1024X768 , 400px or even lower would be the ideal size. However this webpage, http://www.w3schools.com/browsers/browsers_display.asp says that 76% of people use a larger screen resolution than 1024X768.(And it's rising rapidly,2009-57%_2010-76%) I personally have a resolution of 1600x900 and when viewing the page using IE, the images are definitely on the small side (Although I admit, not so small you can’t extract the information.) (Note: In IE increasing the text size does not increase the image size while in Firefox the default is to have the image size increase along with an increase in text size and so the issue is not as great for Firefox users. I think about 25% of people use Firefox. I went ahead and split the difference and set the resolution to 440px, although I am all ears if you think it is too large. I have to admit to having a bias here. Having put all of those hours into them I personally would prefer them on the large size rather than on the small size. What led you to decrease the pixel size? Note that I am not necessarily objecting but only trying to find the optimum pixel size.Dave3457 (talk) 21:53, 30 June 2010 (UTC)

Same as above. Fgnievinski (talk) 16:15, 2 July 2010 (UTC)

Temporary removal of Federal Standards reference.

For now I have removed the reference to the Federal Standard as Steve Quinn has pointed out a second reference to circular polarization handedness on their site that contradicts the present one we are referencing. (I've placed it below) I have sent an email to the Federal Standards website and am waiting for a reply. If you are interested in this issue, the email I sent is posted at Talk:Polarizer/Lengthy_quotes#Email_to_Federal_Standards_website where Steve and I are discussing matters.

This convention matches that of the U.S., Federal Standard 1037C.

Dave3457 (talk) 00:19, 2 July 2010 (UTC)

Is frequency important

In circularly polarized radiation, does the rotation frequency have a fixed (1:1?) ratio with the frequency of the EM radiation/photons ?

If one rotates an aerial or linear polarizer slowly (compared to the EM frequency) is the radiation wholly, slightly, or not at all circularly polarized ?

Should the article clarify the above ? Rod57 (talk) 11:49, 3 August 2010 (UTC)

I assume you are talking about the frequency with which the electric vector rotates. It is, necessarily, the same as the frequency of the radiation. For the simple case used as an illustration, if you consider the vector to be the sum of two orthogonal components, then you can say that the rotation of the sum vector is caused by the fact that the two components are 90 degrees out of phase. The sum vector makes one rotation for one cycle of the components.

As to your second question, I think a "slow" rotation (as you might do by hand) would be better described as a changing direction of linear polarization. For light, we are talking about huge differences in frequency between the light frequency and the rotation frequency. Correct me if I am wrong, but for 600 nm light (red) I calculate a frequency of about 5*10¹⁴ Hz, compared to perhaps 1 Hz for hand rotation. I do think the effect of this rotation might be noticeable in terms of received signal strength for a linearly polarized receiver, and think that a circularly polarized receiver would not be affected by this rotation.

As to your third question, how do you suggest we improve the explanation?

--AJim (talk) 18:25, 4 August 2010 (UTC)

Many thanks. We could just say, when we first talk about the rotation of the electric vector, that the rotation frequency is the same as (or rather replaces) the frequency of the linear oscillations (and say that it is very different than a rotating direction of linear polarization).

Two follow up questions :

Can a single photon be circularly polarized, or is it a collective phenomenon ?

If one did rotate a 1kHz radio transmitter at 500Hz and then at 1kHz, what % of its radiation would be circularly polarized in each case ? Rod57 (talk) 11:46, 5 August 2010 (UTC)

Thanks. I will think about how to incorporate your suggestion into the description. Or be bold, and do it yourself.

I think photons individually satisfy all the polarization phenomena. You should check the photon polarization article. Circular polarization arises simply because the transverse wave description is two-dimensional and therefore it can have two orthogonal components of independent phase and amplitude. I think circular polarization was predicted by Fresnel and maybe Young (and their associates) as an immediate consequence of realizing that light could be described as a transverse wave.

I have not worked out your second question in detail. Maybe you should; it is a good question. Note though that a 1 kHz half-wave antenna would be about 150 km long; it would be a good trick to construct it, much less to rotate it. However, if you could try the experiment, I think the 1 kHz rotation solution would, surprisingly, be linearly polarized because the driving sine wave amplitude would match the antenna rotation frequency, so that one component would be zero. I think the 500 Hz rotation solution might be circularly polarized, but I could be wrong.

--AJim (talk) 14:42, 5 August 2010 (UTC)

Slight rewrite of Handedness convention section

It was drawn to our attention that in the Feynman's lectures, Feynman says that quantum physicists use the “From source” IEEE convention and so I included that information. (Search “Hello everyone!” on this page for the comment.)
I also took the opportunity to do a slight rewrite of the entire section.
Because the IEEE convention seems to be the more dominant convention I reversed the order that the two conventions were presented. I changed the headings of the two conventions identifying them by point of view instead of user. The first convention section is now called “First convention: From the point of view of the source”. I created a third section summarizing who uses which convention and added a comment about how the The Institute for Telecommunication Sciences (ITS) is presently proposing two contradictory conventions of handedness. (I sent them an email several months ago with no response, after trying again I will be sending another to a different email address. Update: They are not updating 1037C any more, it is for archival purposes only. Refer here for email and response. )

I made no substantial changes with regards to who uses which convention except the addition mentioned above and the referenced comment that “Many radio astronomers ...use (the from source) convention.”

I removed the image of the satellite, not being sure what it contributed, here is the code if someone wishes to put it back. [[Image:GPS Satellite NASA art-iif.crop.jpg|thumb|GPS L-band antenna elements (helical) are right-handed as seen from the transmitter.]]
With regards to its caption, note that the helix is right-handed irrespective of which direction you point your thumb, making the “as seen from the transmitter.” statement misleading. Dave3457 (talk) 16:19, 19 January 2011 (UTC)

Bra-ket notation confusing and possibly wrong

The definition

$|\psi \rangle \ {\stackrel {\mathrm {def} }{=}}\ {\begin{pmatrix}\psi _{x}\\\psi _{y}\end{pmatrix}}={\begin{pmatrix}\cos \theta \exp \left(i\alpha _{x}\right)\\\sin \theta \exp \left(i\alpha _{y}\right)\end{pmatrix}}$

appears to define the Bra-ket terms as 2 element vectors, which forces E to be a two element vector. Later this vector appears in a cross product expression which is only defined for 3 element vectors. You should explain that the direction of propagation is along the z axis and make these definitions 3 vectors with 0 z components. However I see no reason to use this notation at all. No one who hasn't had quantum mechanics will understand this.

While it is true that the Jones calculus is defined on a 2-D subspace, a more consistent way to view that is that a 2 x 1 Jones vector really multiplies , on the right hand side, a 3 x 2 matrix whose columns span the transverse plane, orthogonal to the direction of propagation. Perhaps even better would be to explicitly include $e_{x},e_{y}$ unit vectors in the definition. Oh by the way the fact that the plane wave is propagating in the z direction has to be inferred and is not explicitly stated.

If you are going to use unusual math conventions I'd almost rather see quaternions employed here since it makes the notation considerably more compact. — Preceding unsigned comment added by Mattcbro (talk • contribs) 02:37, 17 August 2011 (UTC)

When is the cross product applied? It may be true that most people are not familiar with bra-ket notation, but it is also the case that most people are not familiar with quaternions, and the fact is that bra-ket notation is very suitable in this case since light polarization is quantized by nature. Can you show us how to use quaternions in this case and why it would be better? —Kri (talk) 18:24, 21 August 2011 (UTC)

Okay, I saw where the cross product was applied: in the beginning of the section Mathematical description. —Kri (talk) 18:37, 21 August 2011 (UTC)

I added a simple change that at least now makes it mathematically correct, without changing the spirit of the article whatsoever. Hope that helps. As for the Quaternion approach, there are several ways to do it. One example can be found in this page: http://www.av8n.com/physics/maxwell-ga.htm#sec-plane-waves though it uses the more general context of geometric algebra. Equation (39) on that page tells most of the story. The waves are broken down into a product of three components, one of which encapsulates the Jones calculus. With biquaternions, both the E and H fields are encapsulated in one equation, real quaternions requires two. The interesting part that comes into play is when propagation media alter the polarization, but that's another story.

Does this needs to be a separated article?

Why is this separated from Polarization (waves) ? --TiagoTiago (talk) 23:21, 29 October 2011 (UTC)

For what it is worth, Elliptical polarization and linear polarization also have their own pages. Dave3457 (talk) 03:14, 30 October 2011 (UTC)

Paragraph from polarizer page belongs here if anywhere

I removed the following paragraph for a couple of reasons. First, I don’t think it was in the interest of the readers for the article to suddenly start talking in terms of quantum mechanics. Second, I'm pretty sure statements made in it were not true. First, the Heisenberg uncertainty principle does not allow you to imagine traveling particles with a distinct position and momentum. Also, photons can’t stop spinning. Whoever put it their, may I suggest you correct it and put it in the quantum mechanics section in this article. Dave3457 (talk) 04:49, 22 November 2013 (UTC)

collapse of paragraph removed

The illusion of a continuous 'wave' is also a mental construct. We might imagine the animation of this single electric field a step closer to physical fact if we supposed the moving helix were fixed as an unmoving record of the arrow's effect and the clocklike circle were itself in motion from the lower right to the upper left in the illustration. The circle serves only as a framing device for the arrow’s rotating motion. But is the photon that actually moves, symbolized here as the point at the center of that circle, i.e., the axis of that rotating ‘arrow.’ Representing the instantaneous electric field as a vector magnitude, the arrow appears to rotate, but in fact the photon spins as it manifests the field. Linear polarization stops the spin.

Reversal of Handedness by Reflection

This explanation appears to be inadequate for several reasons. Firstly, only a polished metal mirror gives a phase shift to reflected light waves, whereas a glass mirror with metal backing does not phase shift light waves. Secondly, if both orthogonal components are phase shifted by the same amount when reflected, the handedness of the circularly polarised light should not change.

A better explanation is with the quantum (photon) model of light rather than the classical (wave) model. For example, a better explanation could be: "Circularly-polarized light is made of photons with their spins parallel to their momentum. The mirror reverses the photons' momentum but does not affect their spins, thus reversing the handedness of the circularly polarised light."

Of course there is no doubt a valid classical (wave) explanation of this phenomenon, but I don't know what it is.

--User:Xaviergisz

Other Orthogonal Decompositions

Really, an edit war. About the Circular polarization article. I think there are two important points alluded to here, first that the orthogonal Cartesian components do not need to be "horizontal" and "vertical". S and P polarizations are very useful, for instance. Second, that any polarization state can be described as the sum of a right and a left handed circular component. Maybe there is a better way to say it. I do think this is a good place to point it out, and not irrelevant. --AJim (talk) 03:33, 14 November 2014 (UTC)

S and P are the same as horizontal and vertical, so the first point is moot. As for the second point, it might belong in Polarization (waves), not here -- in fact, it's already mentioned at the end of Polarization state; in circular polarization, a particular orthogonal basis has already been chosen. Fgnievinski (talk) 12:25, 14 November 2014 (UTC)

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Conventions are confused and incorrect in the article

In Optics we use the second convention, where left-handed (ccw) circularly polarized wave traces a RIGHT handed helix, so from the perspective of the source and and CONSTANT position the wave rotates counter-clockwise in time, and from the perspective of an observer and CONSTANT time the wave rotates counter-clockwise as it travels TOWARDS the observer.

Similarly a right-handed circular polarized wave traces a LEFT handed helix in space, and from the perspective of the source and constant position the wave rotates clockwise, and from the perspective of the observer and constant time, the wave rotates clockwise. From the perspective of the source the left handed helix travels counter-clockwise.

Visually take this left-handed helix and translate it forward, away from the source. At a constant position (a plane normal to the propagation), the helix travels through it and the wave will be rotating clockwise in the plane.

For the "first" convention, used in engineering and quantum mechanics, the left-handed polarization corresponds to the left handed helix.

The article is confused.

Article issues and classification

Reassess to C-class. The article fails the B-class criteria (#1 and #4). There are March 2011 and June 2021 "citation needed" tags and an April 2018 "overly lengthy quotations" tag. There are unsourced sentences, paragraphs, subsections, and sections. -- Otr500 (talk) 17:27, 27 February 2023 (UTC)