Phenomena leading to the polarization of light. The nature of the polarization of light. Malus' law. Where does polarized light come from?

polarization of light. Basic theoretical information

The phenomenon of light polarization is the phenomenon of the occurrence of a certain orientation of the light wave vector in space [main literature 1, 2, 3] .

It is known from Maxwell's theory that an electromagnetic wave is transverse, i.e., , where is the direction of wave propagation. The orientation of a vector in a plane can be determined by the following reasoning and observations.

Suppose first that the vector(Fig. 1) fixed, i.e., does not change its position in the plane perpendicular to the direction of wave propagation. In this case, the projections of the vector onto various planes passing through x, will be different.

Rice. 1. and - two arbitrary planes passing through the direction of wave propagation x

For example, in fig. 1 in sq. , and in sq. , where is the angle between the planes and .

The difference in the projections of the vector on the plane and should lead to the fact that the wave will exhibit different properties with respect to the planes and .

Experience: in the general case, waves propagating directly from the source do not exhibit such properties. The obtained experimental fact means that the above assumption about the fixed position of the vector in the plane perpendicular to the direction of wave propagation does not correspond to reality.

Such a conclusion is in accordance with the nature of the radiation. A light wave from a natural source consists of many trains of waves emitted by individual atoms. The oscillation plane (i.e., the plane drawn through the direction of the wave vector and the direction of the beam) for each train is randomly oriented. Therefore, in natural light, in a plane perpendicular to the beam, oscillations of all possible directions of the vector are simultaneously present (Fig. 2). The probabilities of their realization are the same.

Rice. 2. Vector snapshot natural light in a plane perpendicular to the direction of wave propagation

Therefore, the value of the vector , averaged over the observation time, will be the same in any plane passing through the direction of the beam. This should result in the wave exhibiting the same properties with respect to any of these planes. This is exactly what is observed in experience.

For ease of analysis of some processes of light manifestation, natural light can be considered as a certain transverse wave resulting from all trains, which can be considered monochromatic, in which the direction of the vector in a plane perpendicular to the direction of propagation quickly and randomly replace each other [Supplementary literature 2, 3]

Direction of wave propagation;

Circular polarization - right or left, depending on the direction of rotation of the induction vector;

Elliptical polarization - a case intermediate between circular and linear polarizations.

Incoherent radiation may not be polarized, or be fully or partially polarized in any of the above ways. In this case, the concept of polarization is understood statistically.

In the theoretical consideration of polarization, the wave is assumed to propagate horizontally. Then we can speak of vertical and horizontal linear polarizations of the wave.

Linear Circular Elliptical

Phenomenon theory

An electromagnetic wave can be decomposed (both theoretically and practically) into two polarized components, for example polarized vertically and horizontally. Other expansions are possible, for example, in a different pair of mutually perpendicular directions, or into two components having left and right circular polarization. When trying to expand a linearly polarized wave into circular polarizations (or vice versa), two half-intensity components will appear.

From both quantum and classical points of view, polarization can be described by a two-dimensional complex vector ( Jones vector). Photon polarization is one implementation of the q-bit.

Antenna radiation usually has linear polarization.

By changing the polarization of light upon reflection from the surface, one can judge the surface structure, optical constants, and sample thickness.

If the scattered light is polarized, then using a polarizing filter with a different polarization, it is possible to limit the passage of light. The intensity of light passing through polarizers obeys the Malus law. LCDs work on this principle.

Some living beings, such as bees, are able to distinguish the linear polarization of light, which gives them additional opportunities for orientation in space. It has been found that some animals, such as the peacock mantis shrimp, are able to distinguish circularly polarized light, that is, light with circular polarization.

Discovery history

The discovery of polarized light waves was preceded by the work of many scientists. In 1669, the Danish scientist E. Bartholin reported his experiments with calcareous spar (CaCO3) crystals, most often in the form of a regular rhombohedron, which were brought by sailors returning from Iceland. He was surprised to find that a beam of light passing through a crystal splits into two beams (now called ordinary and extraordinary). Bartholin conducted a thorough study of the phenomenon of double refraction discovered by him, but he could not give an explanation. Twenty years after the experiments of E. Bartholin, his discovery attracted the attention of the Dutch scientist H. Huygens. He himself began to investigate the properties of Iceland spar crystals and gave an explanation for the phenomenon of double refraction on the basis of his wave theory of light. At the same time, he introduced important concept the optical axis of the crystal, during rotation around which there is no anisotropy of the properties of the crystal, i.e., their dependence on the direction (of course, not all crystals have such an axis). In his experiments, Huygens went further than Bartholin, passing both beams that emerged from an Icelandic spar crystal through a second similar crystal. It turned out that if the optical axes of both crystals are parallel, then further decomposition of these rays no longer occurs. If the second rhombohedron is rotated by 180 degrees around the direction of propagation of an ordinary ray, then when passing through the second crystal, the extraordinary ray undergoes a shift in the direction opposite to the shift in the first crystal, and both rays will come out of such a system connected into one beam. It was also found that, depending on the angle between the optical axes of the crystals, the intensity of the ordinary and extraordinary rays changes. These studies brought Huygens close to the discovery of the phenomenon of light polarization, but he could not take a decisive step, since light waves in his theory were assumed to be longitudinal. To explain the experiments of H. Huygens, I. Newton, who adhered to the corpuscular theory of light, put forward the idea of the absence of axial symmetry of the light beam and this made important step understanding the polarization of light. In 1808, the French physicist E. Malus, looking through a piece of Icelandic spar at the windows of the Luxembourg Palace in Paris, shining in the rays of the setting sun, noticed to his surprise that at a certain position of the crystal, only one image was visible. Based on this and other experiments, and relying on Newton's corpuscular theory of light, he suggested that corpuscles in sunlight are randomly oriented, but after reflection from some surface or passing through an anisotropic crystal, they acquire a certain orientation. Such "ordered" light he called polarized.

Stokes parameters

Depiction of polarization in terms of Stokes parameters on the Poincaré sphere

In general, a plane monochromatic wave has right or left elliptical polarization. Full characteristic ellipse is given by three parameters, for example, the half-lengths of the sides of the rectangle in which the polarization ellipse is inscribed A 1 , A 2 and the phase difference φ, or the semi-axes of the ellipse a , b and angle ψ between the axis x and the major axis of the ellipse. It is convenient to describe an elliptically polarized wave based on the Stokes parameters:

, ,

Only three of them are independent, because the identity is true:

If we introduce an auxiliary angle χ, defined by the expression (the sign corresponds to the right, and - to the left polarization), then we can obtain the following expressions for the Stokes parameters:

Based on these formulas, it is possible to characterize the polarization of a light wave in a clear geometric way. In this case, the Stokes parameters , , are interpreted as the Cartesian coordinates of a point lying on the surface of a sphere of radius . The angles and have the meaning of the spherical angular coordinates of this point. Such a geometric representation was proposed by Poincare, so this sphere is called the Poincaré sphere.

Along with , , the normalized Stokes parameters , , are also used. For polarized light .

Literature

Akhmanov S.A., Nikitin S.Yu. - Physical optics, 2nd edition, M. - 2004.
Born M., Wolf E. - Fundamentals of Optics, 2nd edition, revised, trans. from English, M. - 1973

Notes

Wikimedia Foundation. 2010 .

Wave polarization
Photon polarization

See what "Polarization of light" is in other dictionaries:

POLARIZATION OF LIGHT- physical. optical characteristic. radiation, which describes the transverse anisotropy of light waves, i.e., non-equivalence dec. directions in a plane perpendicular to the light beam. The first indications of the transverse anisotropy of a light beam were obtained ... Physical Encyclopedia

POLARIZATION OF LIGHT Modern Encyclopedia

Light polarization- POLARIZATION OF LIGHT, orderliness in the orientation of the intensity vector of the electric E and magnetic H fields of a light wave in a plane perpendicular to the propagation of light. There is a linear polarization of light, when E remains constant ... ... Illustrated Encyclopedic Dictionary

light polarization- polarization A property of light characterized by spatio-temporal ordering of the orientation of the magnetic and electric vectors. Notes 1. Depending on the types of ordering, they distinguish: linear polarization, elliptical ... ...

POLARIZATION OF LIGHT- (lat. from polus). The property of rays of light which, when reflected or refracted, lose their ability to be reflected or refracted again in known directions. Dictionary of foreign words included in the Russian language. Chudinov A.N.,… … Dictionary of foreign words of the Russian language

POLARIZATION OF LIGHT- orderliness in the orientation of the intensity vectors of electric E and magnetic H fields of a light wave in a plane perpendicular to the light beam. Distinguish between the linear polarization of light when E preserves permanent referral(plane ... ... Big Encyclopedic Dictionary

polarization [of light]- Orderliness of the orientation of the vector of the electromagnetic field of the light wave in a plane perpendicular to the direction of propagation of the light beam; the principle of P. is used in the design of a polarizing microscope [Arefiev V.A., Lisovenko L.A. ... ... Technical Translator's Handbook

light polarization- orderliness in the orientation of the vectors of strengths of electric E and magnetic H fields of a light wave in a plane perpendicular to the light beam. Distinguish linear polarization of light when E maintains a constant direction (plane ... ... encyclopedic Dictionary

polarization [of light]- polarization polarization [of light]. The ordering of the orientation of the vector of the electromagnetic field of the light wave in a plane perpendicular to the direction of propagation of the light beam; the principle of P. is used in the design of a polarizing microscope ... Molecular biology and genetics. Dictionary.

light polarization- šviesos poliarizacija statusas T sritis fizika atitikmenys: engl. polarization of light vok. Lichtpolarisation, f rus. light polarization, f pranc. polarization de la lumière, f … Fizikos terminų žodynas

Light polarization

Lecture 3

We know that light is an electromagnetic wave, for which the change in vectors and , occurring with frequency in a mutually plane, is written as follows:

A vector has a physiological effect on the eye. Visible wavelength range: (0.38 ÷ 0.760) µm or (0.38 ÷ 0.76) 10 -6 m or (400 ÷ 760) nm. The highest sensitivity of the eye for λ = 550 µm (green light).

Let's remember that shear waves are called those in which vibrations are made in the direction of their propagation. Electromagnetic waves are transverse .

Suppose we have a light source - an incandescent lamp. Light is the total electromagnetic radiation many atoms. The waves emitted by the lamp will be chaotic in space, rapidly replacing each other directed for the vector (respectively for ). Such radiation is natural light .

Recall the result of adding two mutually perpendicular vibrations:

Phase difference

When adding two harmonic mutually perpendicular oscillations of the same frequency, depending on the phase difference, the end of the resulting vector can oscillate in one plane or move along an ellipse (in a particular case, along a circle).

Linear polarization Elliptical polarization (right, left)

Elliptical polarization (right, left) Circular polarization (right, left) a = b

So, when adding 2 coherent plane-parallel waves, the resulting wave can be linearly polarized, elliptically polarized and circularly polarized. Hence the name polarization. Light (light beam), in which the oscillations of the light vector are somehow ordered, are called polarized . plane of polarization is called a plane parallel to the oscillations of the vector. In the future, we will always talk about the plane of oscillation of the vector, since it is the vector (light intensity) that has a physiological effect on the human eye. If in a light beam the oscillations of all vectors occur only in a certain plane, then such a transverse wave is called plane polarized or linearly polarized .

In the plane of polarization, all vectors of the light beam have this plane of oscillation, r is the direction of propagation of the light beam.

To detect and analyze linearly polarized light, plates are cut in a certain way from tourmaline crystals. As it turned out, in experience, they have the ability to transmit light vibrations only in a certain direction of the vector.

Devices that produce polarized light from natural light are called polarizers , and the devices by which polarized light is detected and studied are analyzers . The common name for polarizer and analyzer is polaroids . Therefore, tourmaline plates can be used both as polarizers and analyzers. Natural light can be represented as 2 beams of light of the same intensity, but polarized in 2 mutual directions.

Direction of wave propagation;

Circular polarization - right or left, depending on the direction of rotation of the induction vector;

Elliptical polarization - a case intermediate between circular and linear polarizations.

Incoherent radiation may not be polarized, or be fully or partially polarized in any of the above ways. In this case, the concept of polarization is understood statistically.

In the theoretical consideration of polarization, the wave is assumed to propagate horizontally. Then we can speak of vertical and horizontal linear polarizations of the wave.

Linear Circular Elliptical

Phenomenon theory

From both quantum and classical points of view, polarization can be described by a two-dimensional complex vector ( Jones vector). Photon polarization is one implementation of the q-bit.

Antenna radiation usually has linear polarization.

By changing the polarization of light upon reflection from the surface, one can judge the surface structure, optical constants, and sample thickness.

Discovery history

The discovery of polarized light waves was preceded by the work of many scientists. In 1669, the Danish scientist E. Bartholin reported his experiments with calcareous spar (CaCO3) crystals, most often in the form of a regular rhombohedron, which were brought by sailors returning from Iceland. He was surprised to find that a beam of light passing through a crystal splits into two beams (now called ordinary and extraordinary). Bartholin conducted a thorough study of the phenomenon of double refraction discovered by him, but he could not give an explanation. Twenty years after the experiments of E. Bartholin, his discovery attracted the attention of the Dutch scientist H. Huygens. He himself began to investigate the properties of Iceland spar crystals and gave an explanation for the phenomenon of double refraction on the basis of his wave theory of light. At the same time, he introduced the important concept of the optical axis of a crystal, during rotation around which there is no anisotropy of the properties of the crystal, i.e., their dependence on direction (of course, not all crystals have such an axis). In his experiments, Huygens went further than Bartholin, passing both beams that emerged from an Icelandic spar crystal through a second similar crystal. It turned out that if the optical axes of both crystals are parallel, then further decomposition of these rays no longer occurs. If the second rhombohedron is rotated by 180 degrees around the direction of propagation of an ordinary ray, then when passing through the second crystal, the extraordinary ray undergoes a shift in the direction opposite to the shift in the first crystal, and both rays will come out of such a system connected into one beam. It was also found that, depending on the angle between the optical axes of the crystals, the intensity of the ordinary and extraordinary rays changes. These studies brought Huygens close to the discovery of the phenomenon of light polarization, but he could not take a decisive step, since light waves in his theory were assumed to be longitudinal. To explain the experiments of H. Huygens, I. Newton, who adhered to the corpuscular theory of light, put forward the idea of the absence of axial symmetry of a light beam and thus made an important step towards understanding the polarization of light. In 1808, the French physicist E. Malus, looking through a piece of Icelandic spar at the windows of the Luxembourg Palace in Paris, shining in the rays of the setting sun, noticed to his surprise that at a certain position of the crystal, only one image was visible. Based on this and other experiments, and relying on Newton's corpuscular theory of light, he suggested that corpuscles in sunlight are randomly oriented, but after reflection from a surface or passing through an anisotropic crystal, they acquire a certain orientation. Such "ordered" light he called polarized.

Stokes parameters

Depiction of polarization in terms of Stokes parameters on the Poincaré sphere

In general, a plane monochromatic wave has right or left elliptical polarization. The full characteristic of the ellipse is given by three parameters, for example, the half-lengths of the sides of the rectangle in which the polarization ellipse is inscribed A 1 , A 2 and the phase difference φ, or the semi-axes of the ellipse a , b and angle ψ between the axis x and the major axis of the ellipse. It is convenient to describe an elliptically polarized wave based on the Stokes parameters:

, ,

Only three of them are independent, because the identity is true:

Along with , , the normalized Stokes parameters , , are also used. For polarized light .

Literature

Akhmanov S.A., Nikitin S.Yu. - Physical optics, 2nd edition, M. - 2004.
Born M., Wolf E. - Fundamentals of Optics, 2nd edition, revised, trans. from English, M. - 1973

Notes

Wikimedia Foundation. 2010 .

See what "Polarization of light" is in other dictionaries:

Phys. optical characteristic. radiation, which describes the transverse anisotropy of light waves, i.e., non-equivalence dec. directions in a plane perpendicular to the light beam. The first indications of the transverse anisotropy of a light beam were obtained ... Physical Encyclopedia

Modern Encyclopedia

- (lat. from polus). The property of rays of light which, when reflected or refracted, lose their ability to be reflected or refracted again in known directions. Dictionary of foreign words included in the Russian language. Chudinov A.N.,… … Dictionary of foreign words of the Russian language

Orderliness in the orientation of the intensity vectors of electric E and magnetic H fields of a light wave in a plane perpendicular to the light beam. Distinguish linear polarization of light when E maintains a constant direction (by the plane ... ... Big Encyclopedic Dictionary

Orderliness in the orientation of the vectors of strengths of electric E and magnetic H fields of a light wave in a plane perpendicular to the light beam. Distinguish linear polarization of light when E maintains a constant direction (plane ... ... encyclopedic Dictionary

Polarization polarization [of light]. The ordering of the orientation of the vector of the electromagnetic field of the light wave in a plane perpendicular to the direction of propagation of the light beam; the principle of P. is used in the design of a polarizing microscope ... Molecular biology and genetics. Dictionary.