Sources of radiation physics. Types of radiation

Every person is exposed to different types of radiation on a daily basis. For those who are not familiar with physical phenomena, has a poor idea of ​​what this process means and where it comes from.

Radiation in physics Is the formation of a new electromagnetic field, formed by the reaction of particles charged with an electric current, in other words, it is a certain flow of electromagnetic waves that propagate around.

Properties of the radiation process

This theory was laid down by M. Faraday in the 19th century, and was continued and developed by Maxwell D. It was he who was able to give all research a rigorous mathematical formula.

Maxwell was able to deduce and structure the laws of Faraday, from which he determined that all electromagnetic waves move at the same speed of light. Thanks to his work, some phenomena and actions in nature became explainable. As a result of his conclusions, the emergence of electrical and radio technology became possible.

Charged particles define characteristics radiation. Also, the process has strong influence interaction of charged particles with magnetic fields to which she aspires.

For example, when it interacts with atomic substances, the speed of movement of a particle changes, it first slows down, and then stops moving further, in science this phenomenon is called bremsstrahlung.

Can be found different types of this phenomenon, some are created by nature itself, and others with the help of human intervention.

However, the very law of changing the type of cure is the same for everyone. The electromagnetic field is separated from the charged element, but it moves at the same speed.

The characteristic of the field directly depends on the speed with which the movement itself occurs, as well as what size the charged particle has. If it does not collide with anything while moving, then its speed does not change and, therefore, it does not create radiation.

But, if during movement it collides with different particles, then the speed changes, part of its own field is disconnected, and turns into free. It turns out that the formation of magnetic waves occurs only when the particle velocity changes.

Various factors can affect the speed, hence different types of radiation are formed, for example, it can be bremsstrahlung. There are also dipole, multipole radiation, they are formed when a particle inside itself changes the existing structure.

It is important that the field always has momentum, energy.

Since in the interaction of a positron and an electron, the formation of free fields is possible, while charged particles retain momentum, energy, which is transferred to the electromagnetic field.

Sources and types of radiation

Electromagnetic waves originally existed in nature; in the process of development and creation of new laws of physics, new sources of radiation appeared, which are called artificial, created by man. This type includes X-rays.

In order to feel this process on yourself, you do not need to leave the apartment. Electromagnetic waves surround a person everywhere, it is enough to turn on the light or light a candle. By raising your hand to the light source, you can feel the heat that objects emit. This phenomenon is called.

However, there are other types of it, for example, in the summer months, going to the beach, a person receives ultraviolet radiation, which comes from the sun's rays.

Every year, at the prophylactic examination, they undergo such a procedure as fluorography, in order to perform a medical examination, special X-ray equipment is used, which also gives radiation.

It is also used in medicine, most often used in physiotherapy of patients. Also, this type is used in children's lasers. Also, in the treatment of some diseases, radiation therapy is used. This type is called gamma because the wavelengths are very short.

This phenomenon is possible due to the complete coincidence of charged particles that interact with the light source.

Many have heard of radiation, it is also one of the types of radiation.

It is formed by decay chemical elements, which are radioactive, that is, the process occurs due to the fact that the nuclei of particles are split into atoms, and they emit radioactive waves. Radio, television for their broadcasting use radio waves, the waves emitted by them, have long length.

Occurrence of radiation

The electric dipole is the simplest element that produces the phenomenon. However, the process creates specific system, which consists of two particles, vibrating in a different type.

If the particles are in a straight line, when moving towards each other, then part of the electromagnetic field is disconnected, and charged waves are formed.

In physics, such a phenomenon is called non-isotopic, since the resulting energy does not have the same strength. IN this case the speed and location of the elements are not important, since actual emitters must have a large number of elements that have a charge.

The initial state can be changed if the like charged particles begin to pull towards the nucleus, where the distribution of charges takes place. Such a connection can be considered as an electric dipole, since the resulting system will be completely electrically neutral.

If there is no dipole, then it is possible to create a process using a quadrupole. Also in physics, a more complex system for obtaining radiation is distinguished - this is a multipole.

For the formation of such particles, it is necessary to use a circuit with a current; then, during motion, the appearance of quadrupole radiation is possible. It is important to consider that the intensity of the magnetic is much less than that of the electrical type.

Radiation response

In the process of interaction, the particle loses part of its own energy, since a certain force affects it during movement. It, in turn, affects the speed of the wave flow; when it acts, the acting force of movement slows down. This process is called radiation friction.

With this reaction, the strength of the process will be very insignificant, but the speed will be very high and close to the speed of light. This phenomenon can be considered on the example of our planet.

The magnetic field contains quite a lot of energy, so the electrons that are emitted from space cannot reach the planet's surface. However, there are particles of cosmic waves that can reach the earth. Such elements must have a high self-energy loss.

The dimensions of the area of ​​space are also highlighted, this value is important for radiation. This factor affects the formation of the electromagnetic radiation field.

In this state of motion, the particles are not large, but the speed of detachment of the field from the element is equal to the light, and it turns out that the process of creation will be very active. And as a result, short electromagnetic waves are obtained.

In the case when the speed of the particle is high, and is approximately equal to light, then the time for detaching the field increases, this process takes quite a long time and, therefore, electromagnetic waves have a high length. Since their path took longer than usual, and the formation of the field took a rather long time.

In quantum physics, radiation is also used, but when considering, completely different elements are used, these can be molecules, atoms. In this case, the phenomenon of radiation is considered and obeys the laws of quantum mechanics.

Thanks to the development of science, it became possible to make corrections and change the characteristics of the radiation.

Many studies have shown that radiation can negatively affect the human body. It all depends on what kind of radiation and how long the person was exposed to.

It's no secret that when chemical reaction and the decay of nuclear molecules, radiation can occur, which is dangerous for living organisms.

When they disintegrate, instantaneous and rather strong irradiation can occur. The surrounding objects can also emit radiation, it can be cell phones, microwave ovens, laptops.

These objects usually send out short electromagnetic waves. However, accumulation can occur in the body, which affects health.

Radiation

in a broad sense, the emission of rapidly moving charged particles or waves and the formation of their fields. I. - a form of release and distribution of energy. Exist different kinds I. Mechanical I. includes noise, infrasound, and ultrasound. The second group consists of electromagnetic and corpuscular I. The main characteristics of mechanical and electromagnetic I. are frequency and wavelength, the action of any I. depends on their energy. I. are also divided into ionizing and non-ionizing. There are a number of forms of I., in particular: visible - optical I. with a wavelength from 740 nm (red light) to 400 nm (violet light), which determines the visual sensations of a person; ultraviolet - electromagnetic radiation invisible to the eye within the wavelength range from 400 to 10 nm; infrared - optical radiation with a wavelength of 770 nm (that is, more than visible), emitted by heated bodies; sound - excitement sound waves in an elastic (solid liquid and gas) medium, including audible sound (from 16 to 20 kHz), infrasound (less than 16 kHz), ultrasound (from 21 kHz to 1 GHz) and hyperevuk (more than 1 GHz); ionizing - electromagnetic (X-rays and gamma rays) and corpuscular (alpha and beta particles, flux of protons and neutrons) radiation, to one degree or another penetrates into living tissues and produces changes in them associated or with "knocking out") electrons from atoms and molecules, or with direct and indirect generation of ions; electromagnetic - the process of emission of electromagnetic waves and the alternating field of these waves.

EdwART. Glossary of terms of the Ministry of Emergency Situations, 2010

Synonyms:

Antonyms:

See what "Radiation" is in other dictionaries:

Electromagnetic, classic electrodynamics education el. magn. waves with accelerated moving charge. chsami (or alternating currents); into a quantum. the theory of the creation of photons when the state of the quantum changes. systems; the term "I." also used for ... ... Physical encyclopedia

The process of emission and propagation of energy in the form of waves and particles. In the overwhelming majority of cases, radiation is understood as electromagnetic radiation, which in turn can be divided by radiation sources into thermal radiation, ... ... Wikipedia

Outpouring, outpouring, effusion, light, emission, emanation, radiation, radiation, sheaf, vibroacoustic treatment. Dictionary of Russian synonyms. radiation emanation (book) Dictionary of synonyms of the Russian language. Practical guide. M .: Russian language. Z. E. ... ... Synonym dictionary

RADIATION, radiation, cf. (book). Action according to ch. radiate radiate and radiate radiate. Radiation of heat from the sun. Heat radiation. Non-thermal radiation. Radioactive radiation. Dictionary Ushakov. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary

Modern encyclopedia

Electromagnetic process of formation of a free electromagnetic field; the free electromagnetic field itself is also called radiation. Emitting accelerated moving charged particles (eg, bremsstrahlung, synchrotron radiation, ... ... Big Encyclopedic Dictionary

Radiation- electromagnetic, the process of formation of a free electromagnetic field, as well as the free electromagnetic field itself, which exists in the form of electromagnetic waves. Radiation is emitted by accelerated moving charged particles, as well as atoms, ... ... Illustrated Encyclopedic Dictionary

RADIATION, energy transfer by ELEMENTARY PARTICLES OR ELECTROMAGNETIC WAVES. Any ELECTROMAGNETIC RADIATION passes through VACUUM, which distinguishes it from such phenomena as THERMAL CONDUCTIVITY, CONVECTION and sound transmission. In a vacuum ... ... Scientific and technical encyclopedic dictionary

radiation- working electronic equipment. Topics information security EN emanation ... Technical translator's guide

RADIATE, ayu, ayu; not sov. that. Emit rays, emit radiant energy. I. light I. warm. The eyes radiate tenderness (trans.). Ozhegov's Explanatory Dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 ... Ozhegov's Explanatory Dictionary

Radiation, radiation (Radiation, emanation) the body's return to space of the energy contained in it in the form of electromagnetic waves. Samoilov K.I. Marine vocabulary... M. L .: State Naval Publishing House of the NKVMF of the USSR, 1941 ... Marine dictionary

Books

• Radiation in astrophysical plasma, Zheleznyakov V.V. general principles generation and transfer of radiation in astrophysical plasma. It meets the needs of both radio and X-ray ...

Radiation is a physical process that results in the transfer of energy using electromagnetic waves. The process opposite to radiation is called absorption. Let's consider this issue in more detail, and also give examples of radiation in everyday life and nature.

Physics of the origin of radiation

Any body consists of atoms, which, in turn, are formed by positively charged nuclei and electrons, which form electron shells around the nuclei and are negatively charged. Atoms are arranged in such a way that they can be in different energy states, that is, they can have both higher and lower energy. When an atom has the lowest energy, then one speaks of its ground state, any other energy state of the atom is called excited.

The existence of various energy states of an atom is due to the fact that its electrons can be located at certain energy levels. When an electron moves from a higher level to a lower one, the atom loses the energy that it emits into the surrounding space in the form of a photon - a particle that carries electromagnetic waves. On the contrary, the transition of an electron from a lower to a higher high level accompanied by absorption of a photon.

Transfer an electron of an atom to a higher energy level can be done in several ways, which involve the transfer of energy. This can be both the impact on the considered atom of external electromagnetic radiation, and the transfer of energy to it by mechanical or electrical means. In addition, atoms can receive and then release energy as a result of chemical reactions.

Electromagnetic spectrum

Before moving on to examples of radiation in physics, it should be noted that each atom emits a certain amount of energy. This is because the states in which an electron can be in an atom are not arbitrary, but strictly defined. Accordingly, the transition between these states is accompanied by the emission of a certain amount of energy.

Of atomic physics It is known that photons generated as a result of electronic transitions in an atom have energy that is directly proportional to their vibration frequency and inversely proportional to the wavelength (a photon is an electromagnetic wave, which is characterized by propagation speed, length and frequency). Since an atom of matter can only emit a certain set of energies, it means that the wavelengths of the emitted photons are also specific. The set of all these lengths is called the electromagnetic spectrum.

If the wavelength of a photon lies between 390 nm and 750 nm, then they speak of visible light, since a person can perceive it with his own eyes, if the wavelength is less than 390 nm, then such electromagnetic waves have high energy and are called ultraviolet, X-ray or gamma radiation. For lengths greater than 750 nm, a small energy of photons is characteristic; they are called infrared, micro- or radio radiation.

Thermal radiation of bodies

Any body that has a certain temperature other than absolute zero emits energy, in this case one speaks of thermal or temperature radiation. In this case, the temperature determines both the electromagnetic spectrum of thermal radiation and the amount of energy emitted by the body. The higher the temperature, the more energy the body emits into the surrounding space, and the more its electromagnetic spectrum shifts to the high-frequency region. Thermal radiation processes are described by the Stefan-Boltzmann, Planck and Wien laws.

Examples of radiation in everyday life

As it was said above, absolutely any body radiates energy in the form of electromagnetic waves, however, it is not always possible to see this process with the naked eye, since the temperatures of the bodies around us, as a rule, are too low, therefore their spectrum lies in a low-frequency region invisible to humans.

A striking example of radiation in the visible range is an electric incandescent lamp. Passing in a spiral, the electric current heats the tungsten filament up to 3000 K. Such heat leads to the fact that the filament begins to emit electromagnetic waves, the maximum of which falls on the long-wave part of the visible spectrum.

Another example of radiation in the home is a microwave oven, which emits microwaves that are invisible to the human eye. These waves are absorbed by objects containing water, thereby increasing their kinetic energy and, as a consequence, temperature.

Finally, an example of infrared radiation in everyday life is the radiator of a heating battery. We do not see its radiation, but we feel this warmth.

Natural emitting objects

Perhaps the most striking example of radiation in nature is our star - the Sun. The temperature on the surface of the Sun is about, therefore, its maximum radiation falls on a wavelength of 475 nm, that is, lies within the visible spectrum.

The sun heats up the planets around it and their satellites, which also begin to glow. A distinction should be made here between reflected light and thermal radiation. So, our Earth can be seen from space in the form of a blue ball precisely due to the reflected sunlight... If we talk about the thermal radiation of the planet, then it also takes place, but lies in the region of the microwave spectrum (about 10 microns).

Besides reflected light, it is interesting to give another example of radiation in nature, which is associated with crickets. The visible light they emit has nothing to do with thermal radiation and is the result of a chemical reaction between atmospheric oxygen and luciferin (a substance contained in insect cells). This phenomenon is called bioluminescence.

Today we will talk about what radiation is in physics. Let's talk about the nature of electronic transitions and give an electromagnetic scale.

Deity and atom

The structure of matter became the subject of interest of scientists more than two thousand years ago. Ancient Greek philosophers wondered how air differs from fire, and earth from water, why marble is white and coal is black. They created complex systems of interdependent components, refuted or supported each other. And the most incomprehensible phenomena, for example, a lightning strike or a sunrise, were attributed to the action of the gods.

Once, long years Observing the steps of the temple, one scientist noticed: each foot, which stands on a stone, carries away a tiny particle of matter. Over time, the marble changed shape, sagging in the middle. The name of this scientist is Leucippus, and he called the smallest particles atoms, indivisible. This was the beginning of the path to the study of what radiation is in physics.

Easter and light

Then dark times came, science was abandoned. All who tried to study the forces of nature were dubbed witches and sorcerers. But, oddly enough, it was religion that gave impetus to further development science. Research into what radiation is in physics began with astronomy.

The time for celebrating Easter was calculated in those days each time in different ways. The complex system of relationships between the vernal equinox, the 26-day lunar cycle and the 7-day week did not allow compiling date tables for celebrating Easter for more than a couple of years. But the church had to plan everything in advance. Therefore, Pope Leo X ordered the compilation of more accurate tables. This required careful observation of the movement of the moon, stars and the sun. And in the end, Nicolaus Copernicus realized: the Earth is not flat and not the center of the universe. A planet is a ball that revolves around the sun. And the Moon is a sphere orbiting the Earth. Of course, one might ask: "What does all this have to do with what radiation is in physics?" Let's open it now.

Oval and beam

Later, Kepler supplemented the Copernican system by establishing that the planets move in oval orbits, and this movement is uneven. But it was that first step that instilled in humanity an interest in astronomy. And there it was not far to the questions: "What is a star?", "Why do people see its rays?" and "How is one luminary different from another?" But first you have to go from huge objects to the smallest. And then we come to radiation, a concept in physics.

Atom and raisins

At the end of the nineteenth century, enough knowledge was accumulated about the smallest chemical units of matter - atoms. They were known to be electrically neutral, but contain both positively and negatively charged elements.

Many assumptions have been put forward: both that positive charges are distributed in a negative field, like raisins in a roll, and that an atom is a drop of dissimilarly charged liquid parts. But everything was clarified by Rutherford's experience. He proved that in the center of the atom there is a positive heavy nucleus, and light negative electrons are located around it. And the configuration of the shells for each atom is different. This is where the peculiarities of radiation in the physics of electronic transitions lie.

Boron and orbit

When scientists found out that the light negative parts of the atom are electrons, another question arose - why they do not fall on the nucleus. Indeed, according to Maxwell's theory, any moving charge emits, therefore, loses energy. But atoms have existed for as long as the universe, and were not going to annihilate. Bor came to the rescue. He postulated that electrons are in certain stationary orbits around the atomic nucleus, and can only be on them. The transition of an electron between orbits is carried out in a jerk with absorption or emission of energy. This energy can be, for example, a quantum of light. In fact, we have now presented the definition of radiation in particle physics.

Hydrogen and photography

Photography technology was originally conceived as a commercial project. People wanted to stay for centuries, but not everyone could afford to order a portrait from the artist. And the photos were cheap and did not require such a large investment. Then the art of glass and silver nitrate put military affairs at its service. And then science began to take advantage of the advantages of light-sensitive materials.

First of all, the spectra were photographed. It has long been known that hot hydrogen emits specific lines. The distance between them obeyed a certain law. But the spectrum of helium was more complex: it contained the same set of lines as hydrogen, and one more. The second series no longer obeyed the law derived for the first series. Here Bohr's theory came to the rescue.

It turned out that there is only one electron in the hydrogen atom, and it can move from all higher excited orbits to one lower one. This was the first series of lines. Heavier atoms are more complex.

Lens, grating, spectrum

Thus, the beginning of the application of radiation in physics was laid. Spectral analysis is one of the most powerful and reliable methods for determining the composition, amount and structure of a substance.

1. The electronic emission spectrum will tell you what is contained in the object and what the percentage of a particular component is. This method is used by absolutely all fields of science: from biology and medicine to quantum physics.
2. The absorption spectrum will tell you which ions and at which positions are present in the lattice of a solid.
3. The rotational spectrum will demonstrate how far the molecules are inside the atom, how many and what bonds each element has.

And the ranges of application of electromagnetic radiation are countless:

• radio waves explore the structure of very distant objects and the bowels of planets;
• thermal radiation will tell about the energy of the processes;
• visible light will tell you in which directions the brightest stars lie;
• ultraviolet rays will indicate that high-energy interactions are taking place;
• the X-ray spectrum itself allows people to study the structure of matter (including the human body), and the presence of these rays in space objects will notify scientists that the telescope is in focus neutron star, supernova or black hole.

Black body

But there is a special section that studies what thermal radiation is in physics. Unlike atomic, thermal emission of light has a continuous spectrum. And the best model object for calculations is an absolutely black body. This is an object that "catches" all the light falling on it, but does not release it back. Oddly enough, a black body emits, and the maximum wavelength will depend on the temperature of the model. In classical physics, thermal radiation gave rise to a paradox. It turned out that any heated thing had to emit more and more energy until its energy in the ultraviolet range would destroy the universe.

Max Planck was able to resolve the paradox. In the radiation formula, he introduced a new quantity, a quantum. Without giving it a special physical meaning, he opened the whole world. Quantizing quantities is now essential modern science... Scientists realized that fields and phenomena are composed of indivisible elements, quanta. This led to deeper research into matter. For example, modern world belongs to semiconductors. Previously, everything was simple: metal conducts current, other substances are dielectrics. And substances such as silicon and germanium (just semiconductors) behave incomprehensibly in relation to electricity. To learn how to control their properties, it was required to create a whole theory and calculate all p-n capabilities transitions.

§ 1. Heat radiation

In the process of studying the radiation of heated bodies, it was found that any heated body emits electromagnetic waves (light) in a wide frequency range. Hence, thermal radiation is the radiation of electromagnetic waves due to the internal energy of the body.

Thermal radiation occurs at any temperature. However, at low temperatures, only long (infrared) electromagnetic waves are emitted.

We carry out the following quantities characterizing the radiation and absorption of energy by bodies:

energetic luminosityR(T) Is the energy W emitted by 1 m 2 of the surface of a luminous body in 1 s.

W / m 2.

body emissivity r(λ, Т) ( or spectral density of radiant luminosity) Is the energy in a unit wavelength interval emitted by 1 m 2 of the surface of a luminous body in 1 s.

.
.

Here
Is the radiation energy with wavelengths from λ to
.

The relationship between the integrated radiant luminosity and the spectral density of the radiant luminosity is given by the following relationship:

.

.

It was experimentally established that the ratio of emissivity and absorption capacity does not depend on the nature of the body. This means that it is the same (universal) function of wavelength (frequency) and temperature for all bodies. This empirical law was discovered by Kirchhoff and bears his name.

Kirchhoff's law: the ratio of emissivity and absorption capacity does not depend on the nature of the body, it is for all bodies the same (universal) function of wavelength (frequency) and temperature:

.

A body that, at any temperature, completely absorbs all radiation incident on it, is called an absolutely black body of an AHT.

Absorption capacity of an absolutely black body and a.ch.t. (λ, T) is equal to one. This means that the universal Kirchhoff function
identical to the emissivity of a black body
... Thus, to solve the problem of thermal radiation, it was necessary to establish the form of the Kirchhoff function or the emissivity of an absolutely black body.

Analyzing experimental data and applying thermodynamic methods Austrian physicists Joseph Stefan(1835 - 1893) and Ludwig Boltzmann(1844-1906) in 1879 partially solved the problem of radiation of a.ch.t. They obtained a formula for determining the energetic luminosity of an AFC. - R acht (T). According to the Stefan-Boltzmann law

,
.

IN
In 1896, German physicists led by Wilhelm Wien created an ultra-modern experimental setup for those times to study the distribution of radiation intensity by wavelengths (frequencies) in the spectrum of thermal radiation of an absolutely black body. The experiments carried out on this installation: firstly, they confirmed the result obtained by the Austrian physicists J. Stephan and L. Boltzmann; secondly, graphs of the distribution of the intensity of thermal radiation by wavelength were obtained. They were surprisingly similar to the curves obtained earlier by J. Maxwell for the distribution of gas molecules in a closed volume in terms of velocities.

The theoretical explanation of the resulting graphs became the central problem of the late 90s of the 19th century.

English classical physics lord Rayleigh(1842-1919) and sir James Jeans(1877-1946) applied to thermal radiation methods of statistical physics(used the classical law on the equipartition of energy by degrees of freedom). Rayleigh and Jeans applied the method of statistical physics to waves, just as Maxwell applied it to an equilibrium ensemble of particles chaotically moving in a closed cavity. They assumed that for each electromagnetic oscillation, on average, there is an energy equal to kT ( on the electrical energy and on magnetic energy),. Based on these considerations, they obtained the following formula for the emissivity of the a.ch.t .:

.

E
This formula described well the course of the experimental dependence at long wavelengths (at low frequencies). But for short wavelengths (high frequencies or in the ultraviolet region of the spectrum), the classical theory of Rayleigh and Jeans predicted an infinite increase in radiation intensity. This effect is called the ultraviolet catastrophe.

Assuming that the same energy corresponds to a standing electromagnetic wave of any frequency, Rayleigh and Jeans neglected the fact that higher and higher frequencies contribute to radiation as the temperature rises. Naturally, the model they adopted should have led to an infinite increase in the radiation energy at high frequencies. The ultraviolet catastrophe has become a serious paradox in classical physics.

FROM
the next attempt to obtain a formula for the dependence of the emissivity of a.h.t. from the wavelengths was taken by Vin. Using methods classical thermodynamics and electrodynamics Blame it was possible to derive a relationship, the graphic image of which satisfactorily coincided with the short-wave (high-frequency) part of the data obtained in the experiment, but absolutely disagreed with the results of experiments for long wavelengths (low frequencies).

.

From this formula, a relation was obtained linking that wavelength
, which corresponds to the maximum radiation intensity, and the absolute body temperature T (Wien's displacement law):

,
.

This was consistent with the experimental results obtained by Wien, from which it followed that with increasing temperature, the maximum radiation intensity shifts towards shorter wavelengths.

But there was no formula describing the entire curve.

Then Max Planck (1858-1947), who at that time worked in the Department of Physics at the Berlin Kaiser Wilhelm Institute, took up the solution to the problem. Planck was a very conservative member of the Prussian Academy, completely absorbed in the methods of classical physics. He was passionate about thermodynamics. Practically, starting from the moment of defending his thesis in 1879, and almost until the end of the century, for twenty years in a row, Planck was engaged in the study of problems associated with the laws of thermodynamics. Planck understood that classical electrodynamics cannot answer the question of how the energy of equilibrium radiation is distributed over wavelengths (frequencies). The problem that arose was related to the field of thermodynamics. Planck investigated the irreversible process of establishing equilibrium between matter and radiation (light)... To achieve agreement between theory and experiment, Planck deviated from classical theory in only one point: he accepted the hypothesis that light emission occurs in portions (quanta)... The hypothesis adopted by Planck made it possible to obtain such a distribution of energy over the spectrum for thermal radiation, which corresponded to experiment.

.

On December 14, 1900, Planck presented his results to the Berlin Physical Society. This is how quantum physics was born.

The quantum of radiation energy, introduced by Planck into physics, turned out to be proportional to the radiation frequency (and inversely proportional to the wavelength):

.

- a universal constant, now called Planck's constant. It is equal to:
.

Light is a complex material object that has both wave and corpuscular properties.

Wave parameters- wavelength , light frequency and wavenumber .

Corpuscular characteristics- energy and momentum .

The wave parameters of light are related to its corpuscular characteristics using Planck's constant:

.

Here
and
Is the wavenumber.

Planck's constant plays a fundamental role in physics. This dimensional constant allows one to quantify the extent to which quantum effects are essential in describing each specific physical system.

When, according to the conditions of the physical problem, the Planck constant can be considered negligible, a classical (not quantum) description is sufficient.