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Polarization

In electrodynamics, polarization is the property of electromagnetic wave Electromagnetic radiation

Electromagnetic radiation is generally described as a self-propagating wave [i] in space with electric [i] ... 

s, such as light Light

Light is electromagnetic radiation [i] with a wavelength [i] that is visible to the eye [i] or, in a technical [i] ... 

, that describes the direction of their transverse electric field Electric field

In physics [i], the properties of space that surrounds an electric charge [i] can be described using an ele ... 

. More generally, the polarization of a transverse wave Transverse wave

A transverse wave is a wave [i] that causes a disturbance in the medium perpendicular to the direction i ... 

 describes the direction of oscillation in the plane perpendicular to the direction of travel. Longitudinal waves such as sound wave Sound

Sound is a disturbance of mechanical energy [i] that propagates through matter [i] as a wave [i]. ... 

s do not exhibit polarization, because for these waves the direction of oscillation is along the direction of travel.

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Encyclopedia

In electrodynamics, polarization is the property of electromagnetic wave Electromagnetic radiation

Electromagnetic radiation is generally described as a self-propagating wave [i] in space with electric [i] ... 

s, such as light Light

Light is electromagnetic radiation [i] with a wavelength [i] that is visible to the eye [i] or, in a technical [i] ... 

, that describes the direction of their transverse electric field Electric field

In physics [i], the properties of space that surrounds an electric charge [i] can be described using an ele ... 

. More generally, the polarization of a transverse wave Transverse wave

A transverse wave is a wave [i] that causes a disturbance in the medium perpendicular to the direction i ... 

 describes the direction of oscillation in the plane perpendicular to the direction of travel. Longitudinal waves such as sound wave Sound

Sound is a disturbance of mechanical energy [i] that propagates through matter [i] as a wave [i]. ... 

s do not exhibit polarization, because for these waves the direction of oscillation is along the direction of travel.

Theory


Basics - plane waves

The simplest manifestation of polarization to visualize is that of a plane wave, which is a good approximation to most light waves . All electromagnetic waves propagating in free space or in a uniform material of infinite extent have electric Electric field

In physics [i], the properties of space that surrounds an electric charge [i] can be described using an ele ... 

 and magnetic field Magnetic field

In physics [i], a magnetic field is that part of the electromagnetic field [i] that exists when there is ... 

s perpendicular to the direction of propagation. Conventionally, when considering polarization, the electric field vector is described and the magnetic field is ignored since it is perpendicular Perpendicular

In geometry [i], two lines [i] are considered perpendicular if one falls on the other in such a way ... 

 to the electric field and proportional to it. The electric field vector may be arbitrarily divided into two perpendicular components labelled x and y . For a simple harmonic wave Simple harmonic motion

Simple harmonic motion is the motion of a simple harmonic oscillator [i] ... 

, where the amplitude of the electric vector varies in a sinusoidal manner, the two components have exactly the same frequency. However, these components have two other defining characteristics that can differ. First, the two components may not have the same amplitude Amplitude

[i] measure of a [[wave]... 

. Second, the two components may not have the same phase, that is they may not reach their maxima and minima at the same time. The shape traced out in a fixed plane by the electric vector as such a plane wave passes over it , is a description of the polarization state. The following figures show some examples of the evolution of the electric field vector with time , along with its x and y components , and the path traced by the tip of the vector in the plane :




In the figure on the left, the two orthogonal components are in phase. In this case the ratio of the strengths of the two components is constant, so the direction of the electric vector is constant. Since the tip of the vector traces out a single line in the plane, this special case is called linear polarization. The direction of this line depends on the relative amplitudes of the two components.

In the middle figure above, the two orthogonal components have exactly the same amplitude and are exactly ninety degrees out of phase. In this case one component is zero when the other component is at maximum or minimum amplitude. There are two possible phase relationships that satisfy this requirement: the x component can be ninety degrees ahead of the y component or it can be ninety degrees behind the y component. In this special case the electric vector traces out a circle in the plane, so this special case is called circular polarization Circular polarization

In electrodynamics [i], circular polarization of electromagnetic radiation [i] is a polarization [i] suc ... 

. The direction the field rotates in depends on which of the two phase relationships exists. These cases are called right-hand circular polarization and left-hand circular polarization, depending on which way the electric vector rotates.

All other cases, that is where the two components are not in phase and either do not have the same amplitude and/or are not ninety degrees out of phase are called elliptical polarization because the electric vector traces out an ellipse Ellipse

The search term "Elliptical" redirects to this page; for the exercise machine, see Elliptical trainer [i] ... 

 in the plane .

The "cartesian" decomposition of the electric field into x and y components is, of course, arbitrary. Plane waves of any polarization can be described instead by combining waves of opposite circular polarization, for example. The cartesian polarization decomposition is natural when dealing with reflection from surfaces, birefringent Birefringence

Birefringence, or double refraction, is the decomposition of a ray [i] of light [i] into two r ... 

 materials, or synchrotron radiation Synchrotron radiation

Synchrotron radiation is electromagnetic radiation [i], similar to cyclotron radiation [i], but generate ... 

. The circularly polarized modes are a more useful basis for the study of light propagation in stereoisomer Stereoisomerism

Stereoisomers are isomeric molecules [i] whose atomic connectivity is the same but whose atomic a ... 

s.

Incoherent radiation


In nature, electromagnetic radiation is often produced by a large number of individual radiators, producing waves independently of each other. This type of light is described as incoherent. In general there is no single frequency but rather a spectrum Spectrum

A spectrum is a condition or value that is not limited to a specific set of values but can vary infinel... 

 of different frequencies present, and even if filtered to an arbitrarily narrow frequency range, there may not be a consistent state of polarization. However, this does not mean that polarization is only a feature of coherent radiation. Incoherent radiation may show statistical correlation Correlation

In probability theory [i] and statistics [i], correlation, also called correlation coefficient, in ... 

 between the components of the electric field, which can be interpreted as partial polarization. In general it is possible to describe an observed wave field as the sum of a completely incoherent part and a completely polarized part. One may then describe the light in terms of the degree of polarization, and the parameters of the polarization ellipse.

Parameterizing polarization


For ease of visualization, polarization states are often specified in terms of the polarization ellipse, specifically its orientation and elongation. A common parameterization uses the azimuth angle, ? and the ellipticity, e . An ellipticity of zero corresponds to linear polarization and an ellipticity of 1 corresponds to circular polarization. The arctangent of the ellipticity, ? = tan−1 e , is also commonly used. An example is shown in the diagram to the right. An alternative to the ellipticity or ellipticity angle is the eccentricity, however unlike the azimuth angle and ellipticity angle, the latter has no obvious geometrical interpretation in terms of the Poincaré sphere .

Full information on a completely polarized state is also provided by the amplitude and phase of oscillations in two components of the electric field vector in the plane of polarization. This representation was used above to show how different states of polarization are possible. The amplitude and phase information can be conveniently represented as a two-dimensional complex Complex number

In mathematics [i], a complex number is a number [i] of the form
... 

 vector :

Here and denote the amplitude of the wave in the two components of the electric field vector, while and represent the phases. The product of a Jones vector with a complex number of unit modulus Absolute value

In mathematics [i], the absolute value of a real number [i] is its numerical value without regard to it ... 

 gives a different Jones vector representing the same ellipse, and thus the same state of polarization. The physical electric field, as the real part of the Jones vector, would be altered but the polarization state itself is independent of absolute phase. The basis vectors used to represent the Jones vector need not represent linear polarization states . In general any two orthogonal states can be used, where an orthogonal vector pair is formally defined as one having a zero inner product Inner product space

In mathematics [i], an inner product space is a vector space [i] with additional structure, an inner... 

. A common choice is left and right circular polarizations, for example to model the different propagation of waves in two such components in circularly birefringent media or signal paths of coherent detectors sensitive to circular polarization.



Regardless of whether polarization ellipses are represented using geometric parameters or Jones vectors, implicit in the parameterization is the orientation of the coordinate frame. This permits a degree of freedom, namely rotation about the propagation direction. When considering light that is propagating parallel to the surface of the Earth, the terms "horizontal" and "vertical" polarization are often used, with the former being associated with the first component of the Jones vector, or zero azimuth angle. On the other hand, in astronomy Astronomy

Astronomy is the science [i] of celestial objects and phenomena [i] that originate outside the Earth's atmosphere [i] ... 

 the equatorial coordinate system Equatorial coordinate system

The equatorial coordinate system is probably the most widely used celestial coordinate system [i], whose ... 

 is generally used instead, with the zero azimuth corresponding to due north. Another coordinate system frequently used relates to the plane made by the propagation direction and a vector normal to the plane of a reflecting surface. This is known as the plane of incidence. The rays in this plane are illustrated in the diagram to the right. The components of the electric field parallel and perpendicular to this plane are termed p-like and s-like . Light with a p-like electric field is said to be p-polarized, pi-polarized, tangential plane polarized, or is said to be a transverse-magnetic wave. Light with an s-like electric field is s-polarized, also known as sigma-polarized or sagittal plane polarized, or it can be called a transverse-electric wave.

In the case of partially polarized radiation, the Jones vector varies in time and space in a way that differs from the constant rate of phase rotation of monochromatic, purely polarized waves. In this case, the wave field is likely stochastic, and only statistical Statistics

Statistics is a mathematical science [i] pertaining to the collection, analysis, interpretat... 

 information can be gathered about the variations and correlations between components of the electric field. This information is embodied in the coherency matrix:







where angular brackets denote averaging over many wave cycles. Several variants of the coherency matrix have been proposed: the Wiener Norbert Wiener

Norbert Wiener was an American [i] theoretical and applied [i] mathematician [i] ... 

 coherency matrix and the spectral coherency matrix of Richard Barakat measure the coherence of a spectral decomposition of the signal, while the Wolf coherency matrix averages over all time/frequencies.

The coherency matrix contains all of the information on polarization that is obtainable using second order statistics. It can be decomposed into the sum of two idempotent matrices, corresponding to the eigenvector Eigenvalue, eigenvector and eigenspace

In mathematics [i], an of a transformation [i]In this context, only linear transformation [i] ... 

s of the coherency matrix, each representing a polarization state that is orthogonal to the other. An alternative decomposition is into completely polarized and unpolarized components. In either case, the operation of summing the components corresponds to the incoherent superposition of waves from the two components. The latter case gives rise to the concept of the "degree of polarization", i.e. the fraction of the total intensity contributed by the completely polarized component.

The coherency matrix is not easy to visualize, and it is therefore common to describe incoherent or partially polarized radiation in terms of its total intensity , degree of polarization , and the shape parameters of the polarization ellipse. An alternative and mathematically convenient description is given by the Stokes parameters Stokes parameters

The Stokes parameters are a set of values that describe the polarization [i] state of electromagnetic radiation [i] ... 

, introduced by George Gabriel Stokes George Gabriel Stokes

Sir George Gabriel Stokes, 1st Baronet was an Irish [i] mathematician [i] and physicist [i] ... 

 in 1852. The relationship of the Stokes parameters to intensity and polarization ellipse parameters is shown in the equations and figure below.




Here Ip, 2? and 2? are the spherical coordinates Spherical coordinate system

In Mathematics [i], the spherical coordinate system is a coordinate system [i] for representing geometri... 

 of the polarization state in the three-dimensional space of the last three Stokes parameters. Note the factors of two before ? and ? corresponding respectively to the facts that any polarization ellipse is indistinguishable from one rotated by 180°, or one with the semi-axis lengths swapped accompanied by a 90° rotation. The Stokes parameters are sometimes denoted I, Q, U and V.

The Stokes parameters contain all of the information of the coherency matrix, and are related to it linearly by means of the identity matrix plus the three Pauli matrices:

Mathematically, the factor of two relating physical angles to their counterparts in Stokes space derives from the use of second-order moments and correlations, and incorporates the loss of information due to absolute phase invariance.

The figure above makes use of a convenient representation of the last three Stokes parameters as components in a three-dimensional vector space. This space is closely related to the Poincaré sphere, which is the spherical surface occupied by completely polarized states in the space of the vector

All four Stokes parameters can also be combined into the four-dimensional Stokes vector Stokes parameters

The Stokes parameters are a set of values that describe the polarization [i] state of electromagnetic radiation [i] ... 

, which can be interpreted as four-vectors of Minkowski space. In this case, all physically realizable polarization states correspond to time-like, future-directed vectors.

Propagation, reflection and scattering

In a vacuum Vacuum

A vacuum is a volume [i] of space [i] that is substansively empty of matter [i], so that gaseous pressur ... 

, the components of the electric field propagate at the speed of light Speed of light

The speed of light in a vacuum [i] is an important physical constant [i] denoted by the letter c for ... 

, so that the phase of the wave varies in space in time while the polarization state does not. That is:
where k is the wavenumber and positive z is the direction of propagation. As noted above, the physical electric vector is the real part of the Jones vector. When electromagnetic waves interact with matter, their propagation is altered. If this depends on the polarization states of the waves, then their polarization may also be altered.

In many types of media, electromagnetic waves may be decomposed into two orthogonal components that encounter different propagation effects. A similar situation occurs in the signal processing paths of detection systems that record the electric field directly. Such effects are most easily characterized in the form of a complex 2×2 transformation matrix called the Jones matrix:

In general the Jones matrix of a medium depends on the frequency of the waves.

For propagation effects in two orthogonal modes, the Jones matrix can be written as:

where g1 and g2 are complex numbers representing the change in amplitude and phase caused in each of the two propagation modes, and T is a unitary matrix representing a change of basis from these propagation modes to the linear system used for the Jones vectors. For those media in which the amplitudes are unchanged but a differential phase delay occurs, the Jones matrix is unitary, while those affecting amplitude without phase have Hermitian Jones matrices. In fact, since any matrix may be written as the product of unitary and positive Hermitian matrices, any sequence of linear propagation effects, no matter how complex, can be written as the a product of these two basic types of transformations.

Media in which the two modes accrue a differential delay are called birefringent Birefringence

Birefringence, or double refraction, is the decomposition of a ray [i] of light [i] into two r ... 

. Well known manifestations of this effect appear in optical wave plate Wave plate

A wave plate or retarder is an optical [i] device that alters the polarization [i] state of ... 

s
/retarders and in Faraday rotation Faraday effect

In physics [i], the Faraday effect or Faraday rotation is a magneto-optical phenomenon, or an inte ... 

/optical rotation . An easily visualized example is one where the propagation modes are linear, and the incoming radiation is linearly polarized at a 45° angle to the modes. As the phase difference starts to appear, the polarization becomes elliptical, eventually changing to purely circular polarization , then to elliptical and eventually linear polarization with an azimuth angle perpendicular to the original direction, then through circular again , then elliptical with the original azimuth angle, and finally back to the original linearly polarized state where the cycle begins anew. In general the situation is more complicated and can be characterized as a rotation Rotation (mathematics)

In linear algebra [i] and geometry [i], a rotation is a type of transformation from one system of coordi ... 

 in the Poincaré sphere about the axis defined by the propagation modes . Examples for linear , circular and elliptical birefringence are shown in the figure on the left. The total intensity and degree of polarization are unaffected. If the path length in the birefringent medium is sufficient, plane waves will exit the material with a significantly different propagation direction, due to refraction Refraction

Refraction is the change in direction of a wave [i] due to a change in its velocity [i].... 

. For example, this is the case with macroscopic crystal Crystal

In chemistry [i] and mineralogy [i], a crystal is a solid [i] in which the constituent atom [i]s, molecule [i] ... 

s of calcite Calcite

The carbonate mineral [i] calcite is a calcium [i] carbonate [i] corresponding to the ... 

, which present the viewer with two offset, orthogonally polarized images of whatever is viewed through them. It was this effect that provided the first discovery of polarization, by Erasmus Bartholinus in 1669. In addition, the phase shift, and thus the change in polarization state, is usually frequency dependent, which, in combination with dichroism, often gives rise to bright colors and rainbow-like effects.

Media in which the amplitude of waves propagating in one of the modes is reduced are called dichroic Dichroism

Dichroism has two related but distinct meanings in optics [i].... 

. Devices that block nearly all of the radiation in one mode are known as polarizing filters or simply "polarizer Polarizer

A polarizer is a device that converts an unpolarized [i] or mixed-polarization beam of electromagnetic wave [i] ... 

s". In terms of the Stokes parameters, the total intensity is reduced while vectors in the Poincaré sphere are "dragged" towards the direction of the favored mode. Mathematically, under the treatment of the Stokes parameters as a Minkowski 4-vector, the transformation is a scaled Lorentz boost Lorentz transformation

A Lorentz transformation is a linear transformation [i] that preserves the spacetime interval [i] betwee ... 

 . Just as the Lorentz transformation preserves the proper time, the quantity det ? = S02-S12-S22-S32 is invariant within a multiplicative scalar constant under Jones matrix transformations .

In birefringent and dichroic media, in addition to writing a Jones matrix for the net effect of passing through a particular path in a given medium, the evolution of the polarization state along that path can be characterized as the product of an infinite series of infinitesimal steps, each operating on the state produced by all earlier matrices. In a uniform medium each step is the same, and one may write

where J is an overall gain/loss factor. Here D is a traceless matrix such that aDe gives the derivative of e with respect to z. If D is Hermitian the effect is dichroism, while a unitary matrix models birefringence. The matrix D can be expressed as a linear combination of the Pauli matrices, where real coefficients give Hermitian matrices and imaginary coefficients give unitary matrices. The Jones matrix in each case may therefore be written with the convenient construction:

where s is a 3-vector composed of the Pauli matrices and n and m are real 3-vectors on the Poincaré sphere corresponding to one of the propagation modes of the medium. The effects in that space correspond to a Lorentz boost of velocity parameter 2ß along the given direction, or a rotation of angle 2f about the given axis. These transformations may also be written as biquaternions , where the elements are related to the Jones matrix in the same way that the Stokes parameters are related to the coherency matrix. They may then be applied in pre- and post-multiplication to the quaternion representation of the coherency matrix, with the usual exploitation of the quaternion exponential for performing rotations and boosts taking a form equivalent to the matrix exponential equations above .

In addition to birefringence and dichroism in extended media, polarization effects describable using Jones matrices can also occur at interface between two materials of different refractive index. These effects are treated by the Fresnel equations Fresnel equations

The Fresnel equations, deduced by Augustin-Jean Fresnel [i], describe the behaviour of light when moving ... 

. Part of the wave is transmitted and part is reflected, with the ratio depending on angle of incidence and the angle of refraction. In addition, if the plane of the reflecting surface is not aligned with the plane of propagation of the wave, the polarization of the two parts is altered. In general, the Jones matrices of the reflection and transmission are real and diagonal, making the effect similar to that of a simple linear polarizer. For unpolarized light striking a surface at a certain optimum angle of incidence known as Brewster's angle Brewster's angle

Brewster's angle is an optical [i] phenomenon named after the Scottish physicist, Sir David Brewster [i] ... 

, the reflected wave will be completely s-polarized.

Certain effects do not produce linear transformations of the Jones vector, and thus cannot be described with Jones matrices. For these cases it is usual instead to use a 4×4 matrix that acts upon the Stokes 4-vector. Such matrices were first used by Paul Soleillet in 1929, although they have come to be known as Mueller matrices. While every Jones matrix has a Mueller matrix, the reverse is not true. Mueller matrices are frequently used to study the effects of the scattering of waves from complex surfaces or ensembles of particles.

Polarization in nature, science, and technology


Polarization effects in everyday life


Light reflected by shiny transparent materials is partly or fully polarized, except when the light is normal Surface normal

A surface normal, or just normal to a
... 

 to the surface. A polarizing filter, such as a pair of polarizing sunglasses Sunglasses

Sunglasses are a visual aid, variously termed spectacles [i] or glasses [i], which feature lenses that a ... 

, can be used to observe this by rotating the filter while looking through. At certain angles, the reflected light will be reduced or eliminated. Polarizing filters remove light polarized at 90° to the filter's polarization axis. If two polarizers are placed atop one another at 90° angles to one another, no light passes through.


Polarization by scattering is observed as light passes through the atmosphere Earth's atmosphere

Earth's atmosphere is a layer of gases surrounding the planet Earth [i] and retained by the Earth's gravity [i]... 

. The scattered Rayleigh scattering

Rayleigh scattering is the scattering [i] of light [i], or other electromagnetic [i] r... 

 light produces the brightness and color in clear skies. This partial polarization of scattered light can be used to darken the sky in photographs, increasing the contrast. This effect is easiest to observe at sunset Sunset

Sunset, also called sundown in some American English [i] dialect [i]s, is the time at which the Su ... 

, on the horizon at a 90° angle from the setting sun. Another easily observed effect is the drastic reduction in brightness of images of the sky and clouds reflected from horizontal surfaces, which is the main reason polarizing filters are often used in sunglasses. Also frequently visible through polarizing sunglasses are rainbow Rainbow

A rainbow is an optical [i] and meteorological [i] phenomenon that causes a nearly co ... 

-like patterns caused by color-dependent birefringent effects, for example in toughened glass Glass

Glass is a uniform amorphous solid [i] material, usually produced when the viscous molten material cools ... 

  or items made from transparent plastic Plastic

Plastic covers a range of synthetic or semisynthetic polymerization [i] products. ... 

s. The role played by polarization in the operation of liquid crystal display Liquid crystal display

A liquid crystal [i] display is a thin, flat display device [i] made up of any number of color or monochrome [i] ... 

s is also frequently apparent to the wearer of polarizing sunglasses, which may reduce the contrast or even make the display unreadable.


The photograph at the right was taken through polarizing sunglasses and through the rear window of a car. Light from the sky is reflected by the windshield of the other car at an angle, making it mostly horizontally polarized. The rear window is made of tempered glass Toughened glass

Toughened glass or tempered glass is a type of safety glass that has increased strength and will u... 

. Stress in the glass, left from its heat treatment, causes it to alter the polarization of light passing through it, like a wave plate Wave plate

A wave plate or retarder is an optical [i] device that alters the polarization [i] state of ... 

. Without this effect, the sunglasses would block the horizontally polarized light reflected from the other car's window. The stress in the rear window, however, changes some of the horizontally polarized light into vertically polarized light that can pass through the glasses. As a result, the regular pattern of the heat treatment becomes visible.

Biology


Many animal Animal

Animals are a major group of organism [i]s, classified as the kingdom [i] Animalia or ... 

s are apparently capable of perceiving the polarization of light, which is generally used for navigational purposes, since the linear polarization of sky light is always perpendicular to the direction of the sun. This ability is very common among the insect Insect

Insects are invertebrate [i]s that are taxonomically [i] referred to as the class Inse ... 

s, including bee Bee

Bees are flying insect [i]s, closely related to wasp [i]s and ant [i]s. ... 

s, which use this information to orient their communicative dances. Polarization sensitivity has also been observed in species of octopus Octopus

The octopus is a cephalopod [i] of the order [i] Octopoda that inhabits many diverse regio ... 

, squid Squid

Squids are a large, diverse group of marine cephalopod [i]s. ... 

, cuttlefish Cuttlefish

Cuttlefish are marine animals of the order [i] Sepiida belonging to the Cephalopod [i]a class [i] ... 

, and mantis shrimp Mantis shrimp

Mantis shrimp are marine crustaceans belonging to the order [i] Stomatopoda, one part of the ... 

. The rapidly changing, vividly colored skin patterns of cuttlefish, used for communication, also incorporate polarization patterns, and mantis shrimp are known to have polarization selective reflective tissue. Sky polarization was thought to be perceived by pigeon Dove

The pigeons and doves are some 300 species [i] of near passerine [i] bird [i]s in the order Columbiformes [i] ... 

s, which was assumed to be one of their aids in homing Homing pigeon

The homing pigeon is a variety of domesticated Rock Pigeon [i] that has been selectively bred to be able ... 

, but research indicates this is a popular myth.

The naked human eye is weakly sensitive to polarization, without the need for intervening filters. Polarized light creates a very faint pattern near the center of the visual field, called Haidinger's brush Haidinger's brush

Haidinger's brush is an entoptic phenomenon [i] first described by Austrian
... 

. This pattern is very difficult to see, but with practice one can learn to detect polarized light with the naked eye.

Geology


The property of birefringence is widespread in crystalline mineral Mineral

Minerals are natural compounds formed through geological [i] processes. ... 

s, and indeed was pivotal in the initial discovery of polarization. In mineralogy, this property is frequently exploited using polarization microscope Microscope

A microscope is an instrument for viewing objects that are too small to be seen by the naked or unaided... 

s, for the purpose of identifying minerals. See pleochroism.

Chemistry


Polarization is principally of importance in chemistry Chemistry

Chemistry is the science [i] of matter [i] at the atom [i]ic to molecular [i] scale, dealing primarily ... 

 due to the circular dichroism Circular dichroism

Circular dichroism, is the differential absorption of left- and right-handed circularly polarized [i] ... 

 and "optical rotation" exhibited by optically active  molecules Molecule

In chemistry, a molecule is an aggregate of two or more atom [i]s in a definite arrangement held togethe ... 

. It may be measured using a polarimeter.

Polarization may also refer to the through-bond or through-space influence of a nearby functional group on the electronic properties of a covalent bond Covalent bond

Covalent bonding is an intramolecular form of chemical bond [i]ing characterized by the sharing of one o ... 

 or atom.

Astronomy

In many areas of astronomy Astronomy

Astronomy is the science [i] of celestial objects and phenomena [i] that originate outside the Earth's atmosphere [i] ... 

, the study of polarized electromagnetic radiation from outer space Outer space

Outer space, also simply called space, refers to the relatively empty regions of the universe [i] ou... 

 is of great importance. Although not usually a factor in the thermal radiation of star Star

A star is a massive, compact body of plasma [i] in outer space [i] that is held together by its ... 

s, polarization is also present in radiation from coherent astronomical sources , and incoherent sources such as the large radio lobes in active galaxies, and pulsar radio radiation , and is also imposed upon starlight by scattering from interstellar dust Cosmic dust

Cosmic dust is composed of particles in space which are a few molecules [i] to 0.1 mm in size. ... 

. Apart from providing information on sources of radiation and scattering, polarization also probes the interstellar magnetic field Magnetic field

In physics [i], a magnetic field is that part of the electromagnetic field [i] that exists when there is ... 

 via Faraday rotation Faraday effect

In physics [i], the Faraday effect or Faraday rotation is a magneto-optical phenomenon, or an inte ... 

. The polarization of the cosmic microwave background Cosmic microwave background radiation

In cosmology [i], the cosmic microwave background radiation is a form of electromagnetic radiation [i] ... 

 is being used to study the physics of the very early universe. Synchrotron radiation Synchrotron radiation

Synchrotron radiation is electromagnetic radiation [i], similar to cyclotron radiation [i], but generate ... 

 is highly polarised.

Technology

Technological applications of polarization are extremely widespread. Perhaps the most commonly-encountered examples are liquid crystal display Liquid crystal display

A liquid crystal [i] display is a thin, flat display device [i] made up of any number of color or monochrome [i] ... 

s and polarized sunglasses Sunglasses

Sunglasses are a visual aid, variously termed spectacles [i] or glasses [i], which feature lenses that a ... 

.

All radio Radio

Radio is the wireless transmission of signals [i], by modulation [i] of electromagnetic waves [i] ... 

 transmitting and receiving antennas are intrinsically polarized, special use of which is made in radar Radar

RADAR is a system that uses radio [i] waves to detect, determine the direction and distance and/or speed ... 

. Most antennas radiate either horizontal, vertical or circular polarization although eliptical polarization also exists. The electric field or E-plane E-plane and H-plane

The E-plane and H-plane are reference planes for linearly polarized antennas [i]. ... 

 determines the polarization or orientation of the radio wave. Vertical polarization is most often used when it is desired to radiate a radio signal in all directions such as widely distributed mobile units. AM and FM radio uses vertical polarization. Television uses horizontal polarization. Alternating vertical and horizontal polarization is used on satellite communication Communications satellite

A communications satellite is an artificial satellite [i] stationed in space for the purposes of telecommunications [i] ... 

s , to reduce interference between programs on the same frequency Frequency

[i] of the number of times that a repeated event occurs per unit of [[time]... 

 band transmitted from adjacent satellites , allowing for reduced angular separation between the satellites.

In engineering, the relationship between strain and birefringence motivates the use of polarization in characterizing the distribution of stress and strain in prototypes. Electronically controlled birefringent devices are used in combination with polarizing filters as modulators in fiber optics Optical fiber

An optical fiber or fibre is a thin, transparent [i] fiber [i], usually made of glass [i]... 

. Polarizing filters are also used in photography Photography

Photography is the process of making pictures by means of the action of light.... 

. They can deepen the color of a blue sky and eliminate reflections from windows and standing water.

Sky polarization has been exploited in the "sky compass", which was used in the 1950s 1950s

The 1950s was the decade spanning the years 1950 to 1959.... 

 when navigating near the poles of the Earth's magnetic field Earth's magnetic field

Earth [i]'s magnetic field is approximately a magnetic dipole [i], with one pole [i] near ... 

 when neither the sun Sun

|+ The Sun   |+
|-
... 

 nor star Star

A star is a massive, compact body of plasma [i] in outer space [i] that is held together by its ... 

s were visible . It has been suggested, controversially, that the Viking Viking

The term Viking commonly denotes the ship-borne explorers, traders, and warriors of the Norsemen [i] who ... 

s exploited a similar device in their extensive expeditions across the North Atlantic Atlantic Ocean

The Atlantic Ocean is the second-largest ocean [i], covering approximately one-fifth of the Earth [i]'s ... 

 in the 9th 9th century

As a means of recording the passage of time [i] the 9th century was that century [i] that lasted from 801 [i] ... 

 - 11th 11th century

As a means of recording the passage of time [i], the 11th century was that century [i] which lasted from ... 

 centuries, before the arrival of the magnetic compass Compass

A compass is a navigational instrument for finding directions on the earth.... 

 in Europe in the 12th century 12th century

As a means of recording the passage of time [i], the 12th century was that century [i] which lasted from ... 

. Related to the sky compass is the "polar clock", invented by Charles Wheatstone Charles Wheatstone

Sir [i] Charles Wheatstone was a British [i] scientist [i] and inventor [i] of ... 

 in the late 19th century 19th century

The 19th century lasted from 1801 [i] through 1900 [i] in the Gregorian calendar [i].
... 

.

Polarization is also used for some 3D movies 3-D film

In film, the term 3-D is used to describe any visual presentation system that attempts to maintain o... 

, in which the two images for the two eyes are polarized differently, and special filter glasses are used to only present the correct image to the correct eye.

Art

Several visual artists have worked with polarized light and birefringent Birefringence

Birefringence, or double refraction, is the decomposition of a ray [i] of light [i] into two r ... 

 materials to create colorful, sometimes changing images. Most notable is contemporary artist Austine Wood Comarow who has trademarked her work "Polage." By cutting out numerous small pieces of birefringent films such as cellophane and laminating them onto a sheet of plane polarizing filter, Austine creates both interactive works and motorized kinetic images. Examples of her work are exhibited at the Museum of Science, Boston Museum of Science, Boston

The Museum of Science is a Boston [i] landmark, located in Science Park, a plot of... 

, the New Mexico Museum of Natural History, Albuquerque and la Cité des Sciences et de l'Industrie Cité des Sciences et de l'Industrie

... 

, Paris, France.

Other examples of polarization


  • Shear wave S-wave

    A type of seismic wave [i], the S-wave, secondary wave, or shear wave, sometimes called an '... 

    s in elastic materials exhibit polarization. These effects are studied as part of the field of seismology Seismology

    Seismology is the scientific study of earthquake [i]s and the movement of waves through the Earth [i]. ... 

    , where horizontal and vertical polarizations are termed SH and SV, respectively.

See also

  • Antennas Antenna (radio)

    An antenna or aerial is an electrical [i] device designed to transmit [i] or receive [i] ... 

  • Birefringence Birefringence

    Birefringence, or double refraction, is the decomposition of a ray [i] of light [i] into two r ... 

  • Circular dichroism Circular dichroism

    Circular dichroism, is the differential absorption of left- and right-handed circularly polarized [i] ... 

  • Electromagnetic radiation Electromagnetic radiation

    Electromagnetic radiation is generally described as a self-propagating wave [i] in space with electric [i] ... 

  • E-plane and H-plane E-plane and H-plane

    The E-plane and H-plane are reference planes for linearly polarized antennas [i]. ... 

  • Fresnel equations Fresnel equations

    The Fresnel equations, deduced by Augustin-Jean Fresnel [i], describe the behaviour of light when moving ... 

  • Nicol prism Nicol prism

    A Nicol prism is a type of polarizer [i], an optical device used to generate a beam of polarized light [i]... 

  • Optics Optics

    Optics is a branch of physics [i] that describes the behavior and properties of light [i] and the inter ... 

  • Photon polarization Photon polarization

    Photon polarization is the quantum mechanical [i] description of the classical [i] ... 

  • Satellite dish Satellite dish

    A satellite dish is a type of parabolic antenna [i] designed with the specific purpose of transmitting s ... 



Notes and references

  • Principles of Optics, 7th edition, M. Born & E. Wolf, Cambridge University, 1999, ISBN 0-521-64222-1.
  • Fundamentals of polarized light : a statistical optics approach, C. Brosseau, Wiley, 1998, ISBN 0-471-14302-2.
  • Field Guide to Polarization, Edward Collett, SPIE Field Guides vol. FG05, SPIE, 2005, ISBN 0-8194-5868-6.
  • Polarization Optics in Telecommunications, Jay N. Damask, Springer 2004, ISBN 0-387-22493-9.
  • Optics, 4th edition, Eugene Hecht, Addison Wesley 2002, ISBN 0-8053-8566-5.
  • Polarized Light in Nature, G. P. Können, Translated by G. A. Beerling, Cambridge University, 1985, ISBN 0-521-25862-6.
  • Polarised Light in Science and Nature, D. Pye, Institute of Physics, 2001, ISBN 0-7503-0673-4.
  • Polarized Light, Production and Use, William A. Shurcliff, Harvard University, 1962.


External links

  • : Polarized Light in Nature and Technology
  • : Microscopic images made using polarization effects
  • : Animated explanation of polarization
  • .
  • : Interactive Java tutorial