# Polarization (waves)

polarizationpolarizedpolarized lightpolarisationvertical polarizationhorizontal polarizationpolarization of lightpolarizationspolarizingpolarised
Polarization (also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations.wikipedia
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### Circular polarization

circularly polarizedcircularly polarized lightcircular
In circular or elliptical polarization, the fields rotate at a constant rate in a plane as the wave travels.
In electrodynamics, circular polarization of an electromagnetic wave is a polarization state in which, at each point, the electric field of the wave has a constant magnitude but its direction rotates with time at a steady rate in a plane perpendicular to the direction of the wave.

### Light

visible lightvisiblelight source
Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves (shear waves) in solids.
The primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarization, while its speed in a vacuum, 299,792,458 metres per second, is one of the fundamental constants of nature.

### Elliptical polarization

elliptically polarizedellipticalaxial ratio
In circular or elliptical polarization, the fields rotate at a constant rate in a plane as the wave travels.
In electrodynamics, elliptical polarization is the polarization of electromagnetic radiation such that the tip of the electric field vector describes an ellipse in any fixed plane intersecting, and normal to, the direction of propagation.

### Optical rotation

optically activeoptical activityoptically inactive
The most common optical materials (such as glass) are isotropic and do not affect the polarization of light passing through them; however, some materials—those that exhibit birefringence, dichroism, or optical activity—can change the polarization of light. Circular birefringence is also termed optical activity, especially in chiral fluids, or Faraday rotation, when due to the presence of a magnetic field along the direction of propagation.
Optical rotation or optical activity (sometimes referred to as rotary polarization) is the rotation of the plane of polarization of linearly polarized light as it travels through certain materials.

### Laser

laserslaser beamlaser light
Especially impacted are technologies such as lasers, wireless and optical fiber telecommunications, and radar.
Temporal (or longitudinal) coherence implies a polarized wave at a single frequency, whose phase is correlated over a relatively great distance (the coherence length) along the beam.

### Linear polarization

linearly polarizedlinearlinear polarized
In linear polarization, the fields oscillate in a single direction.
See polarization and plane of polarization for more information.

### Radio wave

radio wavesradioradio signal
Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves (shear waves) in solids.
In 1887, Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic waves by experimentally generating radio waves in his laboratory, showing that they exhibited the same wave properties as light: standing waves, refraction, diffraction, and polarization.

### Gravitational wave

gravitational wavesgravitational radiationgravity wave
Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves (shear waves) in solids.
In this case the amplitude of the gravitational wave is constant, but its plane of polarization changes or rotates at twice the orbital rate, so the time-varying gravitational wave size, or 'periodic spacetime strain', exhibits a variation as shown in the animation.

### Radio

radio communicationradio communicationswireless
Polarization is an important parameter in areas of science dealing with transverse waves, such as optics, seismology, radio, and microwaves.
The transmitter sends the modulated electrical energy to a tuned resonant antenna; this structure converts the rapidly changing alternating current into an electromagnetic wave that can move through free space (sometimes with a particular polarization).

### Sound

audiosound wavesound waves
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, also known as shear waves, have the additional property, polarization, and are not a characteristic of sound waves.

### Transverse wave

transversetransverse wavestransversal
Polarization (also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations.
Two-dimensional transverse waves exhibit a phenomenon called polarization.

### Jones calculus

Jones matrixJones vectorJones Vectors
The vector containing e x and e y (but without the z component which is necessarily zero for a transverse wave) is known as a Jones vector.
In optics, polarized light can be described using the Jones calculus, discovered by R. C. Jones in 1941.

### Electromagnetic radiation

electromagnetic waveelectromagnetic waveselectromagnetic
Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves (shear waves) in solids.
Electromagnetic waves can be polarized, reflected, refracted, diffracted or interfere with each other.

### Depolarizer (optics)

depolarizationdepolarizer
A so-called depolarizer acts on a polarized beam to create one which is actually fully polarized at every point, but in which the polarization varies so rapidly across the beam that it may be ignored in the intended applications.
A depolarizer or depolariser is an optical device used to scramble the polarization of light.

### Anisotropy

anisotropicanisotropiesanisotropically
Just considering electromagnetic waves, we note that the preceding discussion strictly applies to plane waves in a homogeneous isotropic non-attenuating medium, whereas in an anisotropic medium (such as birefringent crystals as discussed below) the electric or magnetic field may have longitudinal as well as transverse components.
In fluorescence spectroscopy, the fluorescence anisotropy, calculated from the polarization properties of fluorescence from samples excited with plane-polarized light, is used, e.g., to determine the shape of a macromolecule.

### Stokes parameters

Stokes componentStokes components
An alternative and mathematically convenient description is given by the Stokes parameters, introduced by George Gabriel Stokes in 1852.
The Stokes parameters are a set of values that describe the polarization state of electromagnetic radiation.

### Radar

radar stationradarsradar system
Especially impacted are technologies such as lasers, wireless and optical fiber telecommunications, and radar.
In all electromagnetic radiation, the electric field is perpendicular to the direction of propagation, and the electric field direction is the polarization of the wave.

### Mueller calculus

Mueller matrices
Such matrices were first used by Paul Soleillet in 1929, although they have come to be known as Mueller matrices.
Mueller calculus is a matrix method for manipulating Stokes vectors, which represent the polarization of light.

### Sir George Stokes, 1st Baronet

George StokesSir George StokesStokes
An alternative and mathematically convenient description is given by the Stokes parameters, introduced by George Gabriel Stokes in 1852.
As a physicist, Stokes made seminal contributions to fluid dynamics, including the Navier-Stokes equation, and to physical optics, with notable works on polarization and fluorescence.

### Optical fiber

fiber opticfiber opticsfibre optic
Surface waves or waves propagating in a waveguide (such as an optical fiber) are generally not transverse waves, but might be described as an electric or magnetic transverse mode, or a hybrid mode.
Optical fibers can be used as sensors to measure strain, temperature, pressure, and other quantities by modifying a fiber so that the property to measure modulates the intensity, phase, polarization, wavelength, or transit time of light in the fiber.

### Linear dichroism

diattenuation
When the real or imaginary part of that refractive index is dependent on the polarization state of a wave, properties known as birefringence and polarization dichroism (or diattenuation) respectively, then the polarization state of a wave will generally be altered.
Linear dichroism (LD) or diattenuation is the difference between absorption of light polarized parallel and polarized perpendicular to an orientation axis.

### Degree of polarization

One may then describe the light in terms of the degree of polarization and the parameters of the polarized component.
Degree of polarization (DOP) is a quantity used to describe the portion of an electromagnetic wave which is polarized.

### Birefringence

birefringentdouble refractionbiaxial
The most common optical materials (such as glass) are isotropic and do not affect the polarization of light passing through them; however, some materials—those that exhibit birefringence, dichroism, or optical activity—can change the polarization of light. When the real or imaginary part of that refractive index is dependent on the polarization state of a wave, properties known as birefringence and polarization dichroism (or diattenuation) respectively, then the polarization state of a wave will generally be altered.
Birefringence is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light.

### Photon

photonslight quantalight
According to quantum mechanics, electromagnetic waves can also be viewed as streams of particles called photons.
In such quantum field theories, the probability amplitude of observable events is calculated by summing over all possible intermediate steps, even ones that are unphysical; hence, virtual photons are not constrained to satisfy E=pc, and may have extra polarization states; depending on the gauge used, virtual photons may have three or four polarization states, instead of the two states of real photons.

### Faraday effect

FaradayFaraday Rotationrotation measure
Circular birefringence is also termed optical activity, especially in chiral fluids, or Faraday rotation, when due to the presence of a magnetic field along the direction of propagation.
The Faraday effect causes a rotation of the plane of polarization which is linearly proportional to the component of the magnetic field in the direction of propagation.