Ionizing radiation (hereinafter - IR) is radiation, the interaction of which with matter leads to the ionization of atoms and molecules, i.e. this interaction leads to the excitation of the atom and the detachment of individual electrons (negatively charged particles) from the atomic shells. As a result, deprived of one or more electrons, the atom turns into a positively charged ion - primary ionization occurs. AI includes electromagnetic radiation (gamma radiation) and flows of charged and neutral particles - corpuscular radiation (alpha radiation, beta radiation, and neutron radiation).

Alpha radiation refers to corpuscular radiation. This is a stream of heavy positively charged a-particles (nuclei of helium atoms), resulting from the decay of atoms of heavy elements such as uranium, radium and thorium. Since the particles are heavy, the path of alpha particles in the substance (that is, the path on which they produce ionization) turns out to be very short: hundredths of a millimeter in biological media, 2.5-8 cm in air. Thus, an ordinary sheet of paper or the outer dead layer of the skin is capable of retaining these particles.

However, substances that emit alpha particles are long-lived. As a result of the ingress of such substances into the body with food, air or through wounds, they are carried through the body by the blood stream, deposited in the organs responsible for the metabolism and protection of the body (for example, the spleen or lymph nodes), thus causing internal radiation of the body ... The danger of such internal exposure of the body is high, because these alpha particles create very big number ions (up to several thousand pairs of ions per 1 micron path in tissues). Ionization, in turn, determines a number of features of those chemical reactions that occur in a substance, in particular, in living tissue (the formation of strong oxidants, free hydrogen and oxygen, etc.).

Beta radiation(beta rays, or a stream of beta particles) also belongs to the corpuscular type of radiation. This is a stream of electrons (β - radiation, or, more often, just β - radiation) or positrons (β + - radiation) emitted during the radioactive beta decay of the nuclei of some atoms. Electrons or positrons are formed in the nucleus when a neutron is converted to a proton or a proton to a neutron, respectively.

Electrons are much smaller than alpha particles and can penetrate 10-15 centimeters deep into a substance (body) (compare with hundredths of a millimeter for alpha particles). When passing through a substance, beta radiation interacts with the electrons and nuclei of its atoms, spending its energy on this and slowing down the movement until it stops completely. Due to these properties, for protection against beta radiation, it is enough to have a screen made of organic glass of the appropriate thickness. The use of beta radiation in medicine for superficial, interstitial and intracavitary radiation therapy is based on the same properties.

Neutron radiation- another kind of corpuscular type of radiation. Neutron radiation is a flux of neutrons (elementary particles that have no electrical charge). Neutrons do not have an ionizing effect, but a very significant ionizing effect occurs due to elastic and inelastic scattering by the nuclei of matter.

Substances irradiated by neutrons can acquire radioactive properties, that is, receive the so-called induced radioactivity. Neutron radiation is generated during the operation of particle accelerators, in nuclear reactors, industrial and laboratory installations, during nuclear explosions, etc. Neutron radiation has the greatest penetrating ability. The best materials for protection against neutron radiation are hydrogen-containing materials.

Gamma radiation and x-ray relate to electromagnetic radiation.

The fundamental difference between these two types of radiation lies in the mechanism of their occurrence. X-ray radiation is of extra-nuclear origin, gamma radiation is a product of nuclear decay.

X-ray radiation, discovered in 1895 by the physicist Roentgen. It is invisible radiation capable of penetrating, albeit to varying degrees, into all substances. Represents electromagnetic radiation with a wavelength of the order of - from 10 -12 to 10 -7. The X-ray source is an X-ray tube, some radionuclides (for example, beta emitters), accelerators and electron storage devices (synchrotron radiation).

The X-ray tube has two electrodes - the cathode and the anode (negative and positive electrodes, respectively). When the cathode is heated, electron emission occurs (the phenomenon of the emission of electrons by the surface of a solid or liquid). Electrons escaping from the cathode are accelerated by the electric field and hit the surface of the anode, where they are abruptly decelerated, resulting in X-ray radiation. As well visible light, X-rays cause blackening of the photographic film. This is one of its properties, the main one for medicine - that it is penetrating radiation and, accordingly, the patient can be shone through with its help, and since tissues of different density absorb X-rays in different ways - then we can diagnose many types of diseases of internal organs at the earliest stage.

Gamma radiation is of intranuclear origin. It arises during the decay of radioactive nuclei, the transition of nuclei from an excited state to the ground state, during the interaction of fast charged particles with matter, annihilation of electron-positron pairs, etc.

The high penetrating power of gamma radiation is due to its short wavelength. To weaken the flux of gamma radiation, substances are used that differ in a significant mass number (lead, tungsten, uranium, etc.) and all kinds of high-density compositions (various concretes with metal fillers).

A person is constantly under the influence of various external factors. Some of them are visible, such as weather conditions, and their impact can be controlled. Others are invisible to the human eye and are called radiation. Everyone should know the types of radiation, their role and applications.

A person can meet some types of radiation everywhere. Radio waves are a prime example. They represent vibrations of an electromagnetic nature that are capable of being distributed in space at the speed of light. Such waves carry energy from generators.

The sources of radio waves can be divided into two groups.

1. Natural, these include lightning and astronomical units.
2. Artificial, that is, man-made. They include alternating current emitters. These can be radio communication devices, broadcasting devices, computers and navigation systems.

Human skin is capable of depositing this type of waves on its surface, therefore there is a number negative consequences their impact on humans. Radio wave radiation can slow down the activity of brain structures, as well as cause mutations at the genetic level.

For persons with a pacemaker installed, such exposure is fatal. These devices have a clear maximum allowable radiation level, the rise above it introduces an imbalance in the operation of the stimulator system and leads to its breakdown.

All the effects of radio waves on the body have been studied only on animals, there is no direct evidence of their negative effect on humans, but scientists are still looking for ways of protection. As such effective ways not yet. The only advice is to stay away from dangerous appliances. Since household appliances connected to the network also create a radio wave field around them, it is simply necessary to turn off the power to devices that a person does not use at the moment.

Infrared emission

All types of radiation are related in one way or another. Some of them are visible to the human eye. Infrared radiation is adjacent to the part of the spectrum that the human eye can pick up. It not only illuminates the surface, but is also capable of heating it.

The main natural source of infrared rays is the sun. Man has created artificial emitters, through which the necessary thermal effect is achieved.

Now we need to figure out how useful or harmful this type of radiation is for humans. Virtually all of the long-wavelength infrared radiation is absorbed upper layers skin, therefore, it is not only safe, but also able to increase immunity and enhance recovery processes in tissues.

As for short waves, they can go deep into tissues and cause overheating of organs. The so-called heatstroke is a consequence of exposure to short infrared waves. The symptoms of this pathology are known to almost everyone:

• the appearance of spinning in the head;
• feeling of nausea;
• increase in heart rate;
• visual disturbances characterized by darkening in the eyes.

How can you protect yourself from dangerous influences? It is necessary to observe safety precautions when using heat-protective clothing and screens. The use of short-wave heaters should be accurately dosed, the heating element should be covered with a heat-insulating material, with the help of which the radiation of soft long waves is achieved.

If you think about it, all types of radiation can penetrate tissues. But it was X-ray radiation that made it possible to use this property in practice in medicine.

If we compare the rays of X-ray origin with the rays of light, then the former are very long, which allows them to penetrate even through opaque materials. Such rays are not able to be reflected and refracted. This type of spectrum has a soft and hard component. Soft consists of long waves that can be completely absorbed by human tissues. Thus, constant exposure to long waves leads to cell damage and DNA mutation.

There are a number of structures that are unable to transmit X-rays through them. These include, for example, bone and metals. Based on this, images of human bones are taken in order to diagnose their integrity.

Currently, devices have been created that allow not only taking a fixed picture, for example, of a limb, but also observing the changes taking place with it “online”. These devices help the doctor to perform surgical intervention on the bones under visual control, without making wide traumatic incisions. With the help of such devices, it is possible to study the biomechanics of the joints.

As for the negative effects of X-rays, prolonged contact with them can lead to the development of radiation sickness, which manifests itself in a number of signs:

• neurological disorders;
• dermatitis;
• decreased immunity;
• oppression of normal hematopoiesis;
• development of oncological pathology;
• infertility.

To protect yourself from the dire consequences, when contacting this type of radiation, you need to use shielding shields and pads made of materials that do not let the rays through.

People used to call this type of rays simply - light. This type of radiation is able to be absorbed by the object of influence, partially passing through it and partially reflected. Such properties are widely used in science and technology, especially in the manufacture of optical devices.

All sources of optical radiation are divided into several groups.

1. Thermal ones with a continuous spectrum. Heat is released in them due to the current or the combustion process. These can be electric and halogen incandescent lamps, as well as pyrotechnic products and electric lighting devices.
2. Luminescent, containing gases excited by streams of photons. Energy saving devices and cathodoluminescent devices are such sources. As for radio- and chemiluminescent sources, fluxes in them are excited due to the products of radioactive decay and chemical reactions, respectively.
3. Plasma, whose characteristics depend on the temperature and pressure of the plasma formed in them. These can be gas-discharge, mercury tubular and xenon lamps. Spectral sources and devices of a pulsed nature are no exception.

Optical radiation on the human body acts in combination with ultraviolet radiation, which provokes the production of melanin in the skin. Thus, the positive effect lasts until the threshold value of exposure is reached, beyond which the risk of burns and cutaneous oncopathology is located.

The most famous and widely used radiation, the effects of which can be found everywhere, is ultraviolet radiation. This radiation has two spectra, one of which reaches the earth and participates in all processes on earth. The second is trapped by a layer of ozone and does not pass through it. The ozone layer neutralizes this spectrum, thereby fulfilling a protective role. The destruction of the ozone layer is dangerous by the penetration of harmful rays onto the surface of the earth.

The natural source of this type of radiation is the Sun. A huge number of artificial sources have been invented:

• Erythema lamps, activating the production of vitamin D in the layers of the skin and helping to treat rickets.
• Solariums, which not only allow sunbathing, but also have a healing effect for people with pathologies caused by a lack of sunlight.
• Laser emitters used in biotechnology, medicine and electronics.

As for the impact on the human body, it is twofold. On the one hand, a lack of ultraviolet radiation can cause various diseases. Dosed loading with such radiation helps the immune system, the work of muscles and lungs, and also prevents hypoxia.

All types of influences are divided into four groups:

• the ability to kill bacteria;
• removal of inflammation;
• restoration of damaged tissues;
• reduction of pain.

The negative effects of ultraviolet radiation include the ability to provoke skin cancer with prolonged exposure. Melanoma of the skin is an extremely malignant type of tumor. Such a diagnosis means almost 100 percent impending death.

With regard to the organ of vision, excessive exposure to ultraviolet rays damages the retina, cornea and membranes of the eye. Thus, this type of radiation should be used in moderation. If, under certain circumstances, you have to contact the source for a long time ultraviolet rays, it is necessary to protect the eyes with glasses, and the skin with special creams or clothing.

These are the so-called cosmic rays, which carry the nuclei of atoms of radioactive substances and elements. The flux of gamma radiation has a very high energy and is able to quickly penetrate the cells of the body, ionizing their contents. Destroyed cellular elements act like poisons, decomposing and poisoning the entire body. The process necessarily involves the cell nucleus, which leads to mutations in the genome. Healthy cells are destroyed, and in their place mutant cells are formed, unable to fully provide the body with everything it needs.

This radiation is dangerous because a person does not feel it in any way. The consequences of exposure do not appear immediately, but have a long-term effect. First of all, cells of the hematopoietic system, hair, genitals and lymphoid system are affected.

Radiation is very dangerous by the development of radiation sickness, but even this spectrum has found useful applications:

• it is used to sterilize products, equipment and medical instruments;
• measuring the depth of underground wells;
• measuring the path length of spacecraft;
• impact on plants in order to identify productive varieties;
• in medicine, such radiation is used to conduct radiation therapy in the treatment of oncology.

In conclusion, it must be said that all types of rays are successfully applied by man and are necessary. Thanks to them, plants, animals and people exist. Protection from overexposure should be a priority when working.

Radiation, in its most general form, can be imagined as the emergence and propagation of waves, leading to a disturbance of the field. The propagation of energy is expressed in the form of electromagnetic, ionizing, gravitational and Hawking radiation. Electromagnetic waves are electro disturbance magnetic field... They are radio wave, infrared (thermal radiation), terahertz, ultraviolet, X-ray and visible (optical). The electromagnetic wave tends to propagate in any environment. The characteristics of electromagnetic radiation are frequency, polarization and length. The science of quantum electrodynamics studies the nature of electromagnetic radiation most professionally and deeply. It allowed confirming a number of theories that are widely used in various fields of knowledge. Features of electromagnetic waves: mutual perpendicularity of three vectors - wave, and the strength of the electric field and magnetic field; the waves are transverse, and the tension vectors in them oscillate perpendicular to the direction of its propagation.

Thermal radiation arises due to the internal energy of the body itself. Thermal radiation is radiation of a continuous spectrum, the maximum of which corresponds to body temperature. If radiation and matter are thermodynamic, radiation is in equilibrium. This describes Planck's law. But in practice, thermodynamic equilibrium is not observed. So a hotter body tends to cool down, and a colder one, on the contrary, to heat up. This interaction is defined in Kirchhoff's law. Thus, bodies are absorbent and reflective. Ionizing radiation is microparticles and fields that have the ability to ionize matter. It includes: X-rays and radioactive radiation with alpha, beta and gamma rays. In this case, X-rays and gamma rays are shortwave. Beta and alpha particles are particle streams. There are natural and artificial sources of ionization. In nature, these are: decay of radionuclides, rays of space, thermonuclear reaction in the sun. Artificial ones are: radiation from an X-ray apparatus, nuclear reactors and artificial radionuclides. In everyday life, special sensors and dosimeters of radioactive radiation are used. The well-known Geiger counter is able to correctly identify only gamma rays. In science, scintillators are used, which perfectly separate the rays by energy.

Radiation is considered to be gravitational, in which the perturbation of the space-time field occurs at the speed of light. In general relativity, gravitational radiation is caused by Einstein's equations. Tellingly, gravity is inherent in any matter that moves at an accelerated rate. But here a large amplitude of a gravitational wave can only be given by emitting a large mass. Usually gravitational waves are very weak. The device capable of registering them is a detector. Hawking radiation, on the other hand, is rather a hypothetical possibility of emitting particles from a black hole. These processes are studied by quantum physics. According to this theory, a black hole only absorbs matter up to a certain point. Taking into account the quantum moments, it turns out that it is capable of emitting elementary particles.

Monoenergetic ionizing radiation- ionizing radiation, consisting of photons of the same energy or particles of the same type with the same kinetic energy.

Mixed ionizing radiation- ionizing radiation, consisting of particles of various kinds or from particles and photons.

Directional ionizing radiation ionizing radiation with a dedicated direction of propagation.

Natural radiation background- ionizing radiation created by cosmic radiation and radiation of naturally distributed natural radioactive substances (on the Earth's surface, in the near-ground atmosphere, in food, water, in the human body, etc.).

Background - ionizing radiation, consisting of a natural background and ionizing radiation from extraneous sources.

Cosmic radiation- ionizing radiation, which consists of primary radiation coming from outer space and secondary radiation resulting from the interaction of primary radiation with the atmosphere.

Narrow beam of radiation- such geometry of radiation, in which the detector registers only unscattered radiation from the source.

Wide beam of radiation- such geometry of radiation, in which the detector registers unscattered and scattered radiation from the source.

Field ionizing radiation - space-time distribution of ionizing radiation in the considered environment.

Flux of ionizing particles (photons)- the ratio of the number of ionizing particles (photons) dN passing through a given surface during the time interval dt to this interval: F = dN / dt.

Particle energy flow- the ratio of the energy of the incident particles to the time interval Ψ = dЕ / dt.

The flux density of ionizing particles (photons)- the ratio of the flux of ionizing particles (photons) dF

penetrating into the volume of the elementary sphere, to the area of ​​the central cross section dS of this sphere: φ = dF / dS = d 2 N / dtdS. (The energy flux density of the particles is determined in a similar way).

Fluence (transfer) of ionizing particles (photons)- the ratio of the number of ionizing particles (photons) dN penetrating into the volume of the elementary sphere to the area of ​​the central cross-section dS of this sphere: Ф = dN / dS.

Energy spectrum of ionizing particles- the distribution of ionizing particles by their energy. Effective photon energy is the photon energy of such a monoenergetic photon

radiation, the relative attenuation of which in an absorber of a certain composition and a certain thickness is the same as that of the considered non-monoenergetic photon radiation.

Boundary energy of the spectrumβ -radiation - the highest energy of β -particles in the continuous energy spectrum of β -radiation of a given radionuclide.

Albedo of radiation is the ratio of the number of particles (photons) reflected from the interface between two media to the number of particles (photons) incident on the interface.

Delayed emission: particles emitted by decay products, as opposed to particles (neutrons and gamma rays) that arise directly at the time of fission.

Ionization in gases: detachment from an atom or gas molecule of one or more electrons. As a result of ionization, free charge carriers (electrons and ions) appear in the gas and it acquires the ability to conduct electric current.

The term "radiation" encompasses the range of electromagnetic waves including visible spectrum, infrared and ultraviolet regions, as well as radio waves, electric current and ionizing radiation. All the dissimilarity of these phenomena is due only to the frequency (wavelength) of the radiation. Ionizing radiation can be hazardous to human health. AND onizing radiation(radiation) - a type of radiation that changes the physical state of atoms or atomic nuclei, turning them into electrically charged ions or products of nuclear reactions. Under certain circumstances, the presence of such ions or products of nuclear reactions in the tissues of the body can change the course of processes in cells and molecules, and when these events accumulate, it can disrupt the course of biological reactions in the body, i.e. pose a danger to human health.

2. TYPES OF RADIATION

Distinguish between corpuscular radiation, consisting of particles with a mass other than zero, and electromagnetic (photon) radiation.

2.1. Corpuscular radiation

Corpuscular ionizing radiation includes alpha radiation, electron, proton, neutron and meson radiation. Corpuscular radiation, consisting of a stream of charged particles (α-, β-particles, protons, electrons), the kinetic energy of which is sufficient to ionize atoms at

collision, belongs to the class of directly ionizing radiation. Neutrons and other elementary particles do not directly ionize, but in the process of interacting with the medium, they release charged particles (electrons, protons) that can ionize the atoms and molecules of the medium through which they pass.

Accordingly, corpuscular radiation, consisting of a stream of uncharged particles, is called indirectly ionizing radiation.

Fig. 1. Decay scheme for 212 Bi.

2.1.1 Alpha radiation

Alpha particles (α - particles) are the nuclei of a helium atom, emitted during α - decay by some radioactive atoms. α - particle consists of two protons and two neutrons.

Alpha radiation is a flux of nuclei of helium atoms (positively charged and

relatively heavy particles).

Natural alpha radiation as a result of radioactive decay of the nucleus is characteristic of unstable nuclei of heavy elements, starting with an atomic number of more than 83, i.e. for natural radionuclides of the series of uranium and thorium, as well as for artificially obtained transuranium elements.

A typical scheme of α-decay of a natural radionuclide is shown in Fig. 1, and the energy spectrum of α -particles formed during the decay of a radionuclide is shown in

Fig. 2.

Fig. 2 Energy spectrum of α -particles

The possibility of α-decay is associated with the fact that the mass (and, therefore, the total energy of ions) of the α-radioactive nucleus is greater than the sum of the masses of the α-particle and the daughter nucleus formed after α-decay. The excess energy of the original (mother) nucleus is released in the form of the kinetic energy of the α-particle and the recoil of the daughter nucleus. α-particles are positively charged nuclei of helium - 2 He4 and fly out of the nucleus at a speed of 15-20 thousand km / sec. On their way, they produce strong ionization of the environment,

ripping electrons from the orbits of atoms.

The range of α-particles in air is about 5-8 cm, in water - 30-50 microns, in metals - 10-20 microns. During ionization by α-rays, chemical changes substances, and the crystal structure is disturbed solids... Since there is electrostatic repulsion between the α-particle and the nucleus, the probability of nuclear reactions under the influence of α-particles of natural radionuclides (the maximum energy is 8.78 MeV for 214 Po) is very small, and is observed only on light nuclei (Li, Be, B, C , N, Na, Al) with the formation of radioactive isotopes and free neutrons.

2.1.2 Proton radiation

Proton radiation- radiation generated in the process of spontaneous decay of neutron-deficient atomic nuclei or as an output beam of an ion accelerator (for example, synchrophasotoron).

2.1.3 Neutron radiation

Neutron radiation - neutron flux, which transform their energy in elastic and inelastic interactions with atomic nuclei. With inelastic interactions, secondary radiation arises, which can consist of both charged particles and gamma quanta (gamma radiation). In elastic interactions, the usual ionization of matter is possible.

Sources of neutron radiation are: spontaneously fissioning radionuclides; specially made radionuclide neutron sources; accelerators of electrons, protons, ions; nuclear reactors; cosmic radiation.

From the point of view of biological Neutrons are produced in nuclear reactions (in nuclear reactors and in other industrial and laboratory installations, as well as in nuclear explosions).

Neutrons do not possess electric charge... Conventionally, neutrons, depending on the kinetic energy, are divided into fast (up to 10 MeV), superfast, intermediate, slow and thermal. Neutron radiation has a high penetrating power. Slow and thermal neutrons enter into nuclear reactions, as a result, stable or radioactive isotopes can be formed.

A free neutron is an unstable, electrically neutral particle with the following

properties:

These properties of the neutron make it possible to use it, on the one hand, as an object that is being studied and, on the other hand, as a tool for conducting research. In the first case, the unique properties of the neutron are investigated, which is relevant and makes it possible to most reliably and accurately determine the fundamental parameters of the electroweak interaction and, thereby, either confirm or deny Standard model... Availability magnetic moment the neutron already indicates its complex structure, i.e. its "non-elementarity". In the second case, the interaction of unpolarized and polarized neutrons of different energies with nuclei allows them to be used in the physics of nuclei and elementary particles. The study of the effects of violation of spatial parity and invariance with respect to time reversal in various processes - from neutron optics to fission of nuclei by neutrons - is by no means a complete list of the most urgent research directions.

The fact that thermal reactor neutrons have wavelengths comparable to the interatomic distances in matter makes them an indispensable tool for studying condensed media. The interaction of neutrons with atoms is relatively weak, which allows neutrons to penetrate deep enough into matter - this is their significant advantage over X-rays and γ-rays, as well as beams of charged particles. due to the presence of mass, neutrons at the same momentum (hence, at the same wavelength) have significantly less energy than X-rays and γ-rays, and this energy turns out to be comparable to the energy of thermal vibrations of atoms and molecules in matter, which makes it possible to study not only the averaged static atomic structure of a substance, but also the dynamic processes occurring in it. The presence of a magnetic moment in neutrons allows them to be used to study the magnetic structure and magnetic excitations of matter, which is very important for understanding the properties and nature of magnetism of materials.

The scattering of neutrons by atoms is mainly due to nuclear forces, therefore the cross sections for their coherent scattering are in no way related to the atomic number (in contrast to X-ray and γ-rays). Therefore, irradiation of materials with neutrons makes it possible to distinguish the positions of atoms of light (hydrogen, oxygen, etc.) elements, the identification of which is almost impossible using X-rays and γ - rays. For this reason, neutrons are successfully used in the study of biological objects, in materials science, in medicine, and other fields. In addition, the difference in neutron scattering cross sections for different isotopes makes it possible not only to distinguish elements with similar atomic numbers in a material, but also to study their isotopic composition. The presence of isotopes with a negative amplitude of coherent scattering provides a unique opportunity to contrast the media under study, which is also very often used in biology and medicine.

Coherent scattering- scattering of radiation with conservation of frequency and with a phase that differs by π from the phase of the primary radiation. The scattered wave can interfere with the incident wave or other coherently scattered waves.

Today let's 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, after observing the steps of the temple for many years, 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. The study of 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, 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 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 are present in each element.

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. He introduced a new quantity into the radiation formula, a quantum. Without giving it much physical meaning, he opened up a 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.