# What is Polarization: Definition and 660 Discussions

Polarization (also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. A simple example of a polarized transverse wave is vibrations traveling along a taut string (see image); for example, in a musical instrument like a guitar string. Depending on how the string is plucked, the vibrations can be in a vertical direction, horizontal direction, or at any angle perpendicular to the string. In contrast, in longitudinal waves, such as sound waves in a liquid or gas, the displacement of the particles in the oscillation is always in the direction of propagation, so these waves do not exhibit polarization. Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves (shear waves) in solids.
An electromagnetic wave such as light consists of a coupled oscillating electric field and magnetic field which are always perpendicular to each other; by convention, the "polarization" of electromagnetic waves refers to the direction of the electric field. In linear polarization, the fields oscillate in a single direction. In circular or elliptical polarization, the fields rotate at a constant rate in a plane as the wave travels. The rotation can have two possible directions; if the fields rotate in a right hand sense with respect to the direction of wave travel, it is called right circular polarization, while if the fields rotate in a left hand sense, it is called left circular polarization.
Light or other electromagnetic radiation from many sources, such as the sun, flames, and incandescent lamps, consists of short wave trains with an equal mixture of polarizations; this is called unpolarized light. Polarized light can be produced by passing unpolarized light through a polarizer, which allows waves of only one polarization to pass through. The most common optical materials do not affect the polarization of light, however, some materials—those that exhibit birefringence, dichroism, or optical activity—affect light differently depending on its polarization. Some of these are used to make polarizing filters. Light is also partially polarized when it reflects from a surface.
According to quantum mechanics, electromagnetic waves can also be viewed as streams of particles called photons. When viewed in this way, the polarization of an electromagnetic wave is determined by a quantum mechanical property of photons called their spin. A photon has one of two possible spins: it can either spin in a right hand sense or a left hand sense about its direction of travel. Circularly polarized electromagnetic waves are composed of photons with only one type of spin, either right- or left-hand. Linearly polarized waves consist of photons that are in a superposition of right and left circularly polarized states, with equal amplitude and phases synchronized to give oscillation in a plane.Polarization is an important parameter in areas of science dealing with transverse waves, such as optics, seismology, radio, and microwaves. Especially impacted are technologies such as lasers, wireless and optical fiber telecommunications, and radar.

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1. ### B How to build a simple polarization filter

For that we will need a laser pen and two square pieces of opaque, non reflecting material. In both these squares a slit will be cut, wide enough to let a beam of the laser pass through without any refraction effects. First, after the laser has been turned on, one of the squares is placed in...
2. ### I What is “absolute circular polarization fraction” for a pulsar?

In a pulsar paper, two terms were mentioned: circular polarization fraction and absolute circular polarization fraction. 1. What is the absolute circular polarization fraction? 2. What is the difference between them?
3. ### I Problem with the polarization of entangled photons

Consider this thought experiment : we use a source of identically vertically polarized photons, such as produced by a type 0 SPDC. One beam go to Alice and the second to Bob. 1. Whatever measurement Bob makes on its beam, if Alice use a vertically polarized detector, all photons are detected...
4. ### I Can the Last Maxwell's Equation Explain Polarization of a Wire's Insulator?

Hi there! Recently, I have been reading about polarization of a wire's insulator. First of all, I want to see a connection between the last Maxwell's Equation: $$\nabla\times\\B\ =\mu_0\ J\ +\mu_0\ \epsilon_0\ \frac{\partial E}{\partial t}$$ and the polarization. So I draw a simple cartoon...
5. ### I How to distinguish between diagonal vs horizontal/vertical polarization?

I have been working for some time on designing an experiment and have gotten stuck on one particular aspect. I would greatly appreciate any advice that can be offered. I'm using SPDC to produce two polarization-entangled photons. Through the course of the experiment I know that one of the...
6. ### I How different is a calcite crystal from a polarizer?

First of all, I apologize if I use incorrect terminology or I express myself poorly, I am trying my best. That said, I hope you guys are smart enough to understand me despite my shortcomings I know that calcite has birefringence, and I know that if you take calcite crystals and cut them and...
7. ### I Is Calcite a parallel to the Stern-Gerlach experiment?

When light passes through Calcite it is split into two beams opposite polarizations, doubling the image, and this sounds very similar to the Stern-Gerlach experiment where atoms are split into two beams with opposite polarizations The difference is that with light the opposite polarizations are...
8. ### How are polarization test cards created for proving polarized glasses?

I could swear I saw this topic in the forum in the past but haven't found it today. I was curious how polarization test cards are made to prove that a pair of glasses are polarized. Special ink or paint? What is that type of substance called or commonly used for? I'd love to use it for art. Does...
9. ### I Circular polarization and linear polarization of pulsars

Is there more circular polarization or linear polarization in the radiation flux of pulsars? Have any papers discussed this issue?
10. ### I Is there a generator of entangled photons with fixed polarization?

Hello everyone! I don't know where to look for information - maybe here it will work :) Is there a generator of entangled photons with fixed polarization? If not, is it theoretically possible to build or is it against the laws of physics. I need this knowledge for further computer...
11. ### I Hidden phase in polarization tests of Bell's inequality?

Hi there, i must preface with saying my understanding of the problem is limited to undergraduate quantum mechanics, since my spacialization is chemistry. I know the basic principles, like hilbert spaces, vector bases etc... I'm only asking this question because i genuinely want to understand...
12. ### B B-Modes in CMB Polarization - any change since BICEP2 in 2015?

Hello. I was wondering if there have been any further developments on the topic of B-modes in the CMB polarization since this 2015 paper? https://arxiv.org/abs/1502.00612 A Joint Analysis of BICEP2/Keck Array and Planck Data The above paper declares that... 'We find strong evidence for dust...
13. ### I Polarization of Light -- Please help me with some basic questions

I'm studying optics in this semester and one of the topic is polarization of light. Please help me. For ease of understanding we only consider the electric field E, right? I'm confused, if light passes through a polarizer then there will only be one field whose direction of vibration is only...
14. ### I What happens when circular polarization meets a diagonal polarizer?

I'm finding what seems to be conflicting information on this question and could really use some help. It's my understanding that circularly polarized light is composed of two perpendicular linearly polarized components with a 90 degree phase shift between them. When considered individually...
15. ### A How Many Hidden Variables Would It Take to Model Photon Polarization?

Suppose the EPR* concept were true as it would be applied to entangled photon polarization. (Please note: I am not saying it is.) They thought QM was incomplete, because there must exist "elements of reality" (hidden variables) that supplied the highly correlated results on entangled particle...
16. ### Induced polarization for collision between conducting spheres

For this part (b) of this problem, The solution is, However, would a better explanation be: As the spheres are conductors, there will be free electrons within and on the surface of the conductors that will be polarized by the external electric field between the conductor. This will decrease...
17. ### B How to evaluate whether a photon's polarization is in superposition?

Is there an accepted experimental methodology for determining whether a photon's polarization is in superposition or not?
18. ### I Understanding Light Polarization: An Intuitive Explanation

In this thread, I set out an analogy illustrating what quantum entanglement is; further in my post there is a description of the experiment with polarizers and waveplates, corresponding to this model (CHSH inequalities). To understand it, you need to understand what polarization is. I have read...
19. ### I Polarization in Rabi oscillations

Hello! I have 2 levels, with quantum numbers ##(J=0,m_J=0)## and ##(J=1,m_J=1)## and I am a bit confused about whether I can drive Rabi oscillations between them with a fixed laser polarization. Assuming I start in the ##(J=0,m_J=0)##, I would need right-circularly polarized light to drive that...
20. ### I Polarization of photons quantum mechanically

What is it of the photon that gets polarized from a quantum mechanical perspective? In the classical perspective it is often thought that it is the oscillating electric field that gets polarized. But in the quantum case: Is it the de Broglie wave function? Or is it the spin and in case it is the...
21. ### A Selection rule for spectra with circular polarization

Hello everybody! I have a silly question that is blowing my mind. When there is a circular polarized electric field, it can be interpreted as the real part of a complex field, for example $$E(t) = E_0( \hat{x}+i\hat{y}) e^{-i\omega t}$$ Now, for some selection rules it is useful to calculate the...
22. ### Selection rules in electron transitions

Not sure if this belongs in Chemistry or Physics. Even less sure if I understand the selection rules for electron transition correctly; hence this question. So I would be grateful for someone to please correct the following: Letting n and m be energy levels An electron that absorbs a photon...
23. ### I Question about polarization of light by scattering in the atmosphere

My book says: I don't understand why the bottom eye only sees the horizontal red arrow and not the other angles (black arrows)
24. ### I Dipole moment of a cylinder of uniform polarization

If I want to calculate the dipole moment of a dielectric cylinder of uniform polarization perpendicular to its axis, I could multiply the polarization by the volume of the cylinder, which is okay. But another method is to consider the cylinder to be a superposition of two cylinders of equal and...
25. ### I Rotating Polarization with Optics: Exploring the Principle

In optics experiments, I often see the following optics configuration to rotate the polarization of an incident linearly-polarized laser beam. The final reflected beam has its polarization rotated by 90 degrees. My question is: 1) Between the quarter plate and the mirror( reflecting surface)...
26. ### I Polarizing filter synthesis and dynamics

I have found a fair amount of sources for studying polarized light but I haven't found sources discussing synthesis of polarizers in detail along with mechanistic discussion.
27. ### B Exploring the Impact of Photon Polarization on Electron State Changes

How does the polarization of a photon impact the state change of an electron that absorbs it? Presumably the change of an electrons state (including spin) differs based on the polarization of the photon it absorbs.
28. ### I Understanding the Expression for a Linear EM Wave Transmission?

Hi, I have an expression in my textbook that I don't really understand. I have 2 questions regarding this expression for a linear EM wave## \tilde{\vec{E_{0i}}} = (E_{0x} \hat{x} \pm E_{0y} \hat{y}) e^{i(kz- \omega t)}## ## \tilde{\vec{E_{0t}}} = (\sum_j E_{oij} e_{pj}) \hat{e_p} ## ##...
29. ### Characterizing an unknown eliptical polarization

In reality I don't have access to the lab thanks to covid, so I was told that the exiting beam is linearly polarized at +12 degrees when the waveplate is rotated to +70 degrees. I tried plugging these numbers in but got back a complex number for the first component in the Jones vector, when it...
30. ### The polarization charge density ##\rho##p in a charged dialectric

Hi, I have a dialectric cube and inside the center of the cube I have a part where we have Introduced evenly electrons. I have to find the polarization charge density in the 3 regions. I know outside the cube is the vacuum, thus ##\vec{P} = 0## and inside the dialectric (non charged part)...

32. ### B Polarization of a single photon

I was just reading on this forum (and other sources) about the relationship between photon spin and the polarization of light. From what I have gathered, photon spin corresponds to circular polarization: +1 and -1 spins correspond to right and left helical polarizations. So I have a few...

39. ### I Question on circular polarization and the quantum eraser

Looking at the wikipedia page for the (original) quantum eraser (https://en.wikipedia.org/wiki/Quantum_eraser_experiment), quarter-wave plates in front of the slits change photons from being linearly polarized to being circularly polarized. I think this is the case when there is no polarizer in...
40. ### Rotation of the plane of polarization of light by glucose

Hi guys, Online I found this really cool experiment that uses a glucose solution(e.g. in a beaker) to rotate the plane of polarization of a polarized light beam passing through it, of an angle ##\theta## which depends on the frequency of the EM wave. Then, for example, watching white light...
41. ### Calculating the degree of polarization of reflecting light

I am looking for in an equation that's spits out the degree of polarization of reflected light, with incidence angle and the refractive indexes as inputs. an article online article had this graph decribing the degree of polarization as a value between 0 and 1 plotted against the angle of...
42. ### I Polarization mode symmetries of massless particles

I am just reading Carroll's textbook on GR, where at the end of chapter 7.4 Gravitational Wave Solutions he discuss how rotational symmetries in polarization modes are related to spin of massless particles. He then explains that we could expect associated spin-2 particles to gravity - gravitons...
43. ### Polarization of EM waves is preserved after reflection/refraction -- Why?

Hello, here's my question: during the usual derivation of Fresnel's equations, it is assumed that an incident EM wave (plane monochromatic) is transverse electric or magnatic and that it keeps this nature after reflection and transmission. How can this be proven? Thank you!
44. ### Electrostatic Induction in Metals vs Insulators

If we have a small dielectric sphere and a point charge, they will experience an attractive force due to electrostatic induction. (From the elongation/rotation of charges bound to individual atoms). Likewise, if we have a small metallic sphere and a point charge, they will experience an...
45. ### How does a wave with circular polarization behave?

does an em wave with circular polarization behave like a coil, i.e. do perpendicular electromagnetic fields join internally? I am very confused on this subject
46. ### Polarization of a solid sphere of nonconducting material

a) Just using the equations gives us: surface charge density = ## \rho_{\rho s} = kR^2 ## volume charge density = ## \rho_\rho = -4kR ## b) I am not sure here but the Q on the shell is the same as within. If that's the case we can use gauss law to find Q which I guess is the total charge. ##...
47. ### Find the electric field from polarization

Attempt at solution: a) Since I need help with b) this section can be skipped. Results : ##ρ_{psa} = -Pa ## ##ρ_{psb} = Pb ## ##ρ_{p} = \frac {-1}{R^2} \frac {∂(R^2PR)}{∂R} = -3P ## b) This is where I am unsure (first time using gauss law for P) so I need some confirmation here: ## \int...
48. ### Electrostatics problem related to polarization and a cylindrical dielectric

I understand that the above eqs would be used but I clearly don't know how to use them. I am a bit confussed.
49. ### Does a material change the direction of polarization of light?

The polarization referes to the direction of the electric field of a light wave which is to be one direction. The unpolarized light interacts with a material in various ways such as reflection, scattering, refraction. and each of which can transform an unpolarized light into a vertically or...
50. ### Apparatus for a polarization filter rotator dial

Wondering where I can purchase the polarization filter rotator dial equipment? I tried searching online and couldn't find it. I will like to rotate the polarization filter sheets and measure the angle of the rotation but I can't find that equipment online. I have attached the image below: