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Presentation on the topic: Types of radiation

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Currently we know 6 types of radiation - gamma radiation, x-rays, ultraviolet radiation, optical radiation, infrared radiation and radio waves. In this presentation we will look at each of these radiations, namely their properties and applications.

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Radio waves are electromagnetic waves that travel through space at the speed of light (300,000 km/s). Light also belongs to electromagnetic waves, which determines their very similar properties (reflection, refraction, attenuation, etc.). Radio waves carry energy emitted by a generator of electromagnetic oscillations through space. And they are born when the electric field changes, for example, when an alternating electric current passes through a conductor, or when sparks jump through space, i.e. a series of rapidly successive current pulses. Electromagnetic radiation is characterized by frequency, wavelength and power of transferred energy.

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The properties of radio waves allow them to pass freely through air or vacuum. But if a metal wire, antenna or any other conducting body meets on the path of the wave, then they give up their energy to it, thereby causing an alternating electric current in this conductor. But not all the wave energy is absorbed by the conductor; part of it is reflected from the surface. The use of electromagnetic waves in radar is based on this property. The main property of radio waves is that they are able to transfer energy emitted by a generator of electromagnetic oscillations through space. Oscillations occur when the electric field changes.

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Radio waves, as a means for wireless transmission of sound, video and other information over fairly significant distances, have gained popularity and a wide range of use. It is radio waves that underlie the organization of many modern processes, including: radio broadcasting, television, radiotelephone communications, radio meteorology, and radiolocation.

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Infrared radiation is electromagnetic radiation that occupies the spectral region between the red end of visible light (λ = 0.74 μm) and microwave radiation (λ ~ 1-2 mm). The optical properties of substances in infrared radiation differ significantly from their properties in visible radiation. For example, a layer of water of several centimeters is opaque to infrared radiation with λ = 1 μm. Infrared radiation makes up most of the radiation from incandescent lamps, gas-discharge lamps, and about 50% of the sun's radiation. Infrared radiation was discovered in 1800 by the English astronomer W. Herschel. While studying the Sun, Herschel was looking for a way to reduce the heating of the instrument with which the observations were made. Using thermometers to determine the effects of different parts of the visible spectrum, Herschel discovered that the “maximum of heat” lies behind the saturated red color and, possibly, “beyond visible refraction.” This study marked the beginning of the study of infrared radiation.

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The optical properties of substances (transparency, reflectivity, refraction) in the infrared region of the spectrum, as a rule, differ significantly from the same properties in the visible region we are accustomed to. For most metals, the reflectivity for infrared radiation is much greater than for visible light, and increases with increasing wavelength. Materials that are transparent to IR rays and have a high ability to reflect them are used to create IR devices.

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Infrared radiation is used in: medicine; remote control; when painting (for drying paint surfaces); for sterilization of food products; as an anti-corrosion agent (to prevent corrosion of surfaces coated with varnish); checking banknotes for authenticity; for heating the room.

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X-RAY RADIATION - electromagnetic radiation invisible to the eye with a wavelength of 10−7-10−12 m. Discovered in 1895 in Germany. physicist V.K. Roentgen (1845-1923). Emitted during the deceleration of fast electrons in a substance (continuous spectrum) and during transitions of electrons from the outer electron shells of the atom to the inner ones (line spectrum). Sources are: some radioactive isotopes, X-ray tube, accelerators and electron storage devices (synchrotron radiation).

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Using X-rays, you can “enlighten” the human body, as a result of which you can obtain an image of bones, and in modern devices, internal organs (radiography and fluoroscopy). Detection of defects in products (rails, welding seams, etc.) using X-ray radiation is called X-ray flaw detection. In materials science, crystallography, chemistry and biochemistry, X-rays are used to elucidate the structure of substances at the atomic level using X-ray diffraction scattering (X-ray diffraction). A well-known example is the determination of the structure of DNA. Using X-rays, the chemical composition of a substance can be determined. At airports, X-ray television introscopes are actively used, allowing one to view the contents of hand luggage and baggage.

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Optical radiation is light in the broad sense of the word, electromagnetic waves, the lengths of which are in the range with conventional boundaries from 1 nm to 1 mm. In addition to visible radiation perceived by the human eye, this type of radiation includes infrared radiation and ultraviolet radiation. Parallel to the term "O. and." the term “light” historically has less defined spectral boundaries - it often denotes not all optical radiation, but only its visible subrange. Optical research methods are characterized by the formation of directed radiation fluxes using optical systems, including lenses, mirrors, optical prisms, diffraction gratings, etc.

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The wave properties of optical radiation determine the phenomena of light diffraction, light interference, light polarization, etc. At the same time, a number of optical phenomena cannot be understood without invoking the idea of ​​optical radiation as a flow of fast particles - photons. This duality of nature. Optical radiation brings it closer to other objects of the microworld and finds a general explanation in quantum mechanics. The speed of propagation of optical radiation in a vacuum (the speed of light) is about 3·108 m/s. In any other medium, the speed of optical radiation is lower. The refractive index of the medium, determined by the ratio of these velocities (in vacuum and medium), is generally not the same for different wavelengths of optical radiation, which leads to dispersion of optical radiation. Application: In agricultural production, infrared radiation is used mainly for heating young animals and poultry, drying and disinfestation of agricultural products (grain, fruit, etc.), pasteurization of milk, drying of paint and varnish and impregnation coatings.

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High chemical activity, invisible, high penetrating power, kills microorganisms, in small doses has a beneficial effect on the human body (tanning), but in large doses has a negative biological effect: changes in cell development and metabolism, effect on the eyes. Reflectance coefficient of all materials (including metals) decreases with decreasing wavelength of radiation. Wavelength from 10 – 400 nm. Wave frequency from 800*1012 - 3000*1013 Hz.

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A black light lamp is a lamp that emits predominantly in the long-wave ultraviolet region of the spectrum (UVA range) and produces extremely little visible light. To protect documents from counterfeiting, they are often equipped with ultraviolet tags, which are visible only under ultraviolet lighting conditions. Disinfection with ultraviolet (UV) radiation . Sterilization of air and hard surfaces. Water disinfection is carried out by chlorination in combination, as a rule, with ozonation or disinfection with ultraviolet (UV) radiation. Chemical analysis, UV spectrometry. UV spectrophotometry is based on irradiating a substance with monochromatic UV radiation, the wavelength of which changes over time. The substance absorbs UV radiation at different wavelengths to varying degrees. A graph, the ordinate axis of which shows the amount of transmitted or reflected radiation, and the abscissa axis the wavelength, forms a spectrum. The spectra are unique for each substance, which is the basis for the identification of individual substances in a mixture, as well as their quantitative measurement. Catching insects. In medicine (room disinfection).

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Gamma radiation (gamma rays) is a type of electromagnetic radiation with an extremely short wavelength< 5·10−3 нм и, вследствие этого слабо выраженными волновыми свойствами. На шкале электромагнитных волн гамма-излучение граничит с рентгеновским излучением, занимая диапазон более высоких частот и энергий. В области 1-100 кэВ гамма-излучение и рентгеновское излучение различаются только по источнику: если квант излучается в ядерном переходе, то его принято относить к гамма-излучению; если при взаимодействиях электронов или при переходах в атомной электронной оболочке - к рентгеновскому излучению. С точки зрения физики, кванты электромагнитного излучения с одинаковой энергией не отличаются, поэтому такое разделение условно.

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Gamma rays, unlike α-rays and β-rays, are not deflected by electric and magnetic fields and are characterized by greater penetrating power at equal energies and other equal conditions. The main processes that occur during the passage of gamma radiation through matter: photoelectric effect - the energy of a gamma quantum is absorbed by the electron of the shell of the atom, and the electron, performing a work function, leaves the atom, which becomes ionized; the effect of pair formation - a gamma quantum in the field of the nucleus turns into an electron and positron; nuclear photoelectric effect - at energies above several tens of MeV, a gamma quantum is capable of knocking nucleons out of the nucleus.

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Radiation and types of radioactive radiation, the composition of radioactive (ionizing) radiation and its main characteristics. The effect of radiation on matter.

What is radiation

First, let's define what radiation is:

In the process of decay of a substance or its synthesis, the elements of an atom (protons, neutrons, electrons, photons) are released, otherwise we can say radiation occurs these elements. Such radiation is called - ionizing radiation or what is more common radioactive radiation, or even simpler radiation . Ionizing radiation also includes x-rays and gamma radiation.

Radiation is the process of emission of charged elementary particles by matter, in the form of electrons, protons, neutrons, helium atoms or photons and muons. The type of radiation depends on which element is emitted.

Ionization is the process of formation of positively or negatively charged ions or free electrons from neutrally charged atoms or molecules.

Radioactive (ionizing) radiation can be divided into several types, depending on the type of elements from which it consists. Different types of radiation are caused by different microparticles and therefore have different energetic effects on matter, different abilities to penetrate through it and, as a result, different biological effects of radiation.

Alpha, beta and neutron radiation- These are radiations consisting of various particles of atoms.

Gamma and X-rays is the emission of energy.

Alpha radiation

• are emitted: two protons and two neutrons
• penetrating power: low
• irradiation from source: up to 10 cm
• emission speed: 20,000 km/s
• ionization: 30,000 ion pairs per 1 cm of travel
• high

Alpha (α) radiation occurs during the decay of unstable isotopes elements.

Alpha radiation- this is the radiation of heavy, positively charged alpha particles, which are the nuclei of helium atoms (two neutrons and two protons). Alpha particles are emitted during the decay of more complex nuclei, for example, during the decay of atoms of uranium, radium, and thorium.

Alpha particles have a large mass and are emitted at a relatively low speed of an average of 20 thousand km/s, which is approximately 15 times less than the speed of light. Since alpha particles are very heavy, upon contact with a substance, the particles collide with the molecules of this substance, begin to interact with them, losing their energy, and therefore the penetrating ability of these particles is not great and even a simple sheet of paper can hold them back.

However, alpha particles carry a lot of energy and, when interacting with matter, cause significant ionization. And in the cells of a living organism, in addition to ionization, alpha radiation destroys tissue, leading to various damage to living cells.

Of all types of radiation, alpha radiation has the least penetrating power, but the consequences of irradiation of living tissues with this type of radiation are the most severe and significant compared to other types of radiation.

Exposure to alpha radiation can occur when radioactive elements enter the body, for example through air, water or food, or through cuts or wounds. Once in the body, these radioactive elements are carried through the bloodstream throughout the body, accumulate in tissues and organs, exerting a powerful energetic effect on them. Since some types of radioactive isotopes emitting alpha radiation have a long lifespan, when they enter the body, they can cause serious changes in cells and lead to tissue degeneration and mutations.

Radioactive isotopes are actually not eliminated from the body on their own, so once they get inside the body, they will irradiate the tissues from the inside for many years until they lead to serious changes. The human body is not able to neutralize, process, assimilate or utilize most radioactive isotopes that enter the body.

Neutron radiation

• are emitted: neutrons
• penetrating power: high
• irradiation from source: kilometers
• emission speed: 40,000 km/s
• ionization: from 3000 to 5000 ion pairs per 1 cm of run
• biological effects of radiation: high

Neutron radiation- this is man-made radiation arising in various nuclear reactors and during atomic explosions. Also, neutron radiation is emitted by stars in which active thermonuclear reactions occur.

Having no charge, neutron radiation colliding with matter weakly interacts with the elements of atoms at the atomic level, and therefore has high penetrating power. You can stop neutron radiation using materials with a high hydrogen content, for example, a container of water. Also, neutron radiation does not penetrate polyethylene well.

Neutron radiation, when passing through biological tissues, causes serious damage to cells, since it has a significant mass and a higher speed than alpha radiation.

Beta radiation

• are emitted: electrons or positrons
• penetrating power: average
• irradiation from source: up to 20 m
• emission speed: 300,000 km/s
• ionization: from 40 to 150 ion pairs per 1 cm of travel
• biological effects of radiation: average

Beta (β) radiation occurs when one element transforms into another, while the processes occur in the very nucleus of the atom of the substance with a change in the properties of protons and neutrons.

With beta radiation, a neutron is transformed into a proton or a proton into a neutron; during this transformation, an electron or positron (electron antiparticle) is emitted, depending on the type of transformation. The speed of the emitted elements approaches the speed of light and is approximately equal to 300,000 km/s. The elements emitted during this process are called beta particles.

Having an initially high radiation speed and small sizes of emitted elements, beta radiation has a higher penetrating ability than alpha radiation, but has hundreds of times less ability to ionize matter compared to alpha radiation.

Beta radiation easily penetrates through clothing and partially through living tissue, but when passing through denser structures of matter, for example, through metal, it begins to interact with it more intensely and loses most of its energy, transferring it to the elements of the substance. A metal sheet of a few millimeters can completely stop beta radiation.

If alpha radiation poses a danger only in direct contact with a radioactive isotope, then beta radiation, depending on its intensity, can already cause significant harm to a living organism at a distance of several tens of meters from the radiation source.

If a radioactive isotope emitting beta radiation enters a living organism, it accumulates in tissues and organs, exerting an energetic effect on them, leading to changes in the structure of the tissue and, over time, causing significant damage.

Some radioactive isotopes with beta radiation have a long decay period, that is, once they enter the body, they will irradiate it for years until they lead to tissue degeneration and, as a result, cancer.

Gamma radiation

• are emitted: energy in the form of photons
• penetrating power: high
• irradiation from source: up to hundreds of meters
• emission speed: 300,000 km/s
• ionization:
• biological effects of radiation: low

Gamma (γ) radiation is energetic electromagnetic radiation in the form of photons.

Gamma radiation accompanies the process of decay of atoms of matter and manifests itself in the form of emitted electromagnetic energy in the form of photons, released when the energy state of the atomic nucleus changes. Gamma rays are emitted from the nucleus at the speed of light.

When the radioactive decay of an atom occurs, other substances are formed from one substance. The atom of newly formed substances is in an energetically unstable (excited) state. By influencing each other, neutrons and protons in the nucleus come to a state where the interaction forces are balanced, and excess energy is emitted by the atom in the form of gamma radiation

Gamma radiation has a high penetrating ability and easily penetrates clothing, living tissue, and a little more difficult through dense structures of substances such as metal. To stop gamma radiation, a significant thickness of steel or concrete will be required. But at the same time, gamma radiation has a hundred times weaker effect on matter than beta radiation and tens of thousands of times weaker than alpha radiation.

The main danger of gamma radiation is its ability to travel significant distances and affect living organisms several hundred meters from the source of gamma radiation.

X-ray radiation

• are emitted: energy in the form of photons
• penetrating power: high
• irradiation from source: up to hundreds of meters
• emission speed: 300,000 km/s
• ionization: from 3 to 5 pairs of ions per 1 cm of travel
• biological effects of radiation: low

X-ray radiation- this is energetic electromagnetic radiation in the form of photons that arise when an electron inside an atom moves from one orbit to another.

X-ray radiation is similar in effect to gamma radiation, but has less penetrating power because it has a longer wavelength.

Having examined the various types of radioactive radiation, it is clear that the concept of radiation includes completely different types of radiation that have different effects on matter and living tissues, from direct bombardment with elementary particles (alpha, beta and neutron radiation) to energy effects in the form of gamma and x-rays cure.

Each of the radiations discussed is dangerous!

Comparative table with characteristics of different types of radiation

characteristic	Type of radiation
	Alpha radiation	Neutron radiation	Beta radiation	Gamma radiation	X-ray radiation
are emitted	two protons and two neutrons	neutrons	electrons or positrons	energy in the form of photons	energy in the form of photons
penetrating power	low	high	average	high	high
exposure from source	up to 10 cm	kilometers	up to 20 m	hundreds of meters	hundreds of meters
radiation speed	20,000 km/s	40,000 km/s	300,000 km/s	300,000 km/s	300,000 km/s
ionization, steam per 1 cm of travel	30 000	from 3000 to 5000	from 40 to 150	from 3 to 5	from 3 to 5
biological effects of radiation	high	high	average	low	low

As can be seen from the table, depending on the type of radiation, radiation at the same intensity, for example 0.1 Roentgen, will have a different destructive effect on the cells of a living organism. To take this difference into account, a coefficient k was introduced, reflecting the degree of exposure to radioactive radiation on living objects.

Factor k
Type of radiation and energy range	Weight multiplier
Photons all energies (gamma radiation)	1
Electrons and muons all energies (beta radiation)	1
Neutrons with energy < 10 КэВ (нейтронное излучение)	5
Neutrons from 10 to 100 KeV (neutron radiation)	10
Neutrons from 100 KeV to 2 MeV (neutron radiation)	20
Neutrons from 2 MeV to 20 MeV (neutron radiation)	10
Neutrons> 20 MeV (neutron radiation)	5
Protons with energies > 2 MeV (except for recoil protons)	5
Alpha particles, fission fragments and other heavy nuclei (alpha radiation)	20

The higher the “k coefficient”, the more dangerous the effect of a certain type of radiation is on the tissues of a living organism.

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All atoms in an excited state are capable of emitting electromagnetic waves. To do this, they need to go to the ground state, in which their internal energy acquires. The process of such a transition is accompanied by the emission of an electromagnetic wave. Depending on the length, it has different properties. There are several types of such radiation.

Visible light

The wavelength is the shortest distance between a surface of equal phases. Visible light is electromagnetic waves that can be perceived by the human eye. Light wavelengths range from 340 (violet light) to 760 nanometers (red light). The human eye perceives the yellow-green region of the spectrum best.

Infrared radiation

Everything that surrounds a person, including himself, is a source of infrared or thermal radiation (wavelength up to 0.5 mm). Atoms emit electromagnetic waves in this range when they collide chaotically with each other. With each collision, their kinetic energy turns into thermal energy. The atom gets excited and emits waves in the infrared range.

Only a small portion of infrared radiation reaches the Earth's surface from the Sun. Up to 80% is absorbed by air molecules and especially carbon dioxide, which causes the greenhouse effect.

Ultraviolet radiation

The wavelength of ultraviolet radiation is much shorter than that of infrared radiation. The Sun's spectrum also contains an ultraviolet component, but it is blocked by the Earth's ozone layer and does not reach its surface. Such radiation is very harmful to all living organisms.

The length of ultraviolet radiation lies in the region from 10 to 740 nanometers. That small fraction of it that reaches the surface of the Earth along with visible light causes people to tan as a protective reaction of the skin to harmful influences.

Radio waves

Using radio waves up to 1.5 km long, information can be transmitted. This is used in radios and television. Such a long length allows them to bend around the surface of the Earth. The shortest radio waves can be reflected from the upper layers of the atmosphere and reach stations located on the opposite side of the globe.

Gamma rays

Gamma rays are classified as particularly hard ultraviolet radiation. They are formed during the explosion of an atomic bomb, as well as during processes on the surface of stars. This radiation is harmful to living organisms, but the Earth’s magnetosphere does not allow them to pass through. Gamma ray photons have ultra-high energies.

Ionizing radiation (hereinafter referred to as IR) is radiation whose interaction with matter leads to the ionization of atoms and molecules, i.e. this interaction leads to the excitation of the atom and the separation of individual electrons (negatively charged particles) from atomic shells. As a result, deprived of one or more electrons, the atom turns into a positively charged ion - primary ionization occurs. II 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 alpha 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 range of alpha particles in a substance (that is, the path along which they produce ionization) turns out to be very short: hundredths of a millimeter in biological media, 2.5-8 cm in air. Thus, a regular sheet of paper or the outer dead layer of skin can trap these particles.

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

Beta radiation(beta rays, or stream of beta particles) also refers to the corpuscular type of radiation. This is a stream of electrons (β- radiation, or, most often, just β-radiation) or positrons (β+ radiation) emitted during the radioactive beta decay of the nuclei of certain atoms. Electrons or positrons are produced in the nucleus when a neutron converts 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) (cf. hundredths of a millimeter for alpha particles). When passing through matter, beta radiation interacts with the electrons and nuclei of its atoms, expending its energy on this and slowing down the movement until it stops completely. Due to these properties, to protect against beta radiation, it is enough to have an organic glass screen of appropriate thickness. The use of beta radiation in medicine for superficial, interstitial and intracavitary radiation therapy is based on these same properties.

Neutron radiation- another type of corpuscular type of radiation. Neutron radiation is a flow 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 on the nuclei of matter.

Substances irradiated by neutrons can acquire radioactive properties, that is, receive 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 rays and x-rays belong to electromagnetic radiation.

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

X-ray radiation was discovered in 1895 by the physicist Roentgen. This is invisible radiation capable of penetrating, although to varying degrees, into all substances. It is electromagnetic radiation with a wavelength of the order of - from 10 -12 to 10 -7. The source of X-rays 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 strike the surface of the anode, where they are sharply decelerated, resulting in X-ray radiation. Like visible light, X-rays cause photographic film to turn black. This is one of its properties, fundamental for medicine - that it is penetrating radiation and, accordingly, the patient can be illuminated with its help, and since Tissues of different density absorb X-rays differently - we can diagnose many types of diseases of internal organs at a very early stage.

Gamma radiation is of intranuclear origin. It occurs 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, the annihilation of electron-positron pairs, etc.

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

Radioactivity was discovered in 1896 by the French scientist Antoine Henri Becquerel while studying the luminescence of uranium salts. It turned out that uranium salts, without external influence (spontaneously), emitted radiation of an unknown nature, which illuminated photographic plates isolated from light, ionized the air, penetrated through thin metal plates, and caused luminescence of a number of substances. Substances containing polonium 21084Po and radium 226 88Ra had the same property.

Even earlier, in 1985, X-rays were accidentally discovered by the German physicist Wilhelm Roentgen. Marie Curie coined the word "radioactivity".

Radioactivity is a spontaneous transformation (decay) of the nucleus of an atom of a chemical element, leading to a change in its atomic number or a change in mass number. With this transformation of the nucleus, radioactive radiation is emitted.

There is a distinction between natural and artificial radioactivity. Natural radioactivity is the radioactivity observed in unstable isotopes existing in nature. Artificial radioactivity is the radioactivity of isotopes obtained as a result of nuclear reactions.

There are several types of radioactive radiation, differing in energy and penetrating ability, which have different effects on the tissues of a living organism.

Alpha radiation is a stream of positively charged particles, each of which consists of two protons and two neutrons. The penetrating ability of this type of radiation is low. It is retained by a few centimeters of air, several sheets of paper, and ordinary clothing. Alpha radiation can be dangerous to the eyes. It is virtually unable to penetrate the outer layer of skin and does not pose a danger until radionuclides emitting alpha particles enter the body through an open wound, food or inhaled air - then they can become extremely dangerous. As a result of irradiation with relatively heavy, positively charged alpha particles, serious damage to the cells and tissues of living organisms can occur over a certain period of time.

Beta radiation is a stream of negatively charged electrons moving at enormous speed, the size and mass of which are much smaller than alpha particles. This radiation has greater penetrating power compared to alpha radiation. You can protect yourself from it with a thin sheet of metal such as aluminum or a layer of wood 1.25 cm thick. If a person is not wearing thick clothing, beta particles can penetrate the skin to a depth of several millimeters. If the body is not covered with clothing, beta radiation can damage the skin; it passes into the body tissue to a depth of 1-2 centimeters.

Gamma radiation, like X-rays, it is electromagnetic radiation of ultra-high energies. This is radiation of very short wavelengths and very high frequencies. Anyone who has undergone a medical examination is familiar with X-rays. Gamma radiation has a high penetrating ability; you can only protect yourself from it with a thick layer of lead or concrete. X-rays and gamma rays do not carry an electrical charge. They can damage any organs.

All types of radioactive radiation cannot be seen, felt or heard. Radiation has no color, no taste, no smell. The rate of decay of radionuclides practically cannot be changed by known chemical, physical, biological and other methods. The more energy radiation transmits to tissues, the more damage it will cause in the body. The amount of energy transferred to the body is called dose. The body can receive a radiation dose from any type of radiation, including radioactive. In this case, radionuclides can be located outside the body or inside it. The amount of radiation energy that is absorbed per unit mass of the irradiated body is called the absorbed dose and is measured in the SI system in grays (Gy).

For the same absorbed dose, alpha radiation is much more dangerous than beta and gamma radiation. The degree of exposure to various types of radiation on a person is assessed using such a characteristic as equivalent dose. damage body tissues in various ways. In the SI system it is measured in units called sieverts (Sv).

Radioactive decay is the natural radioactive transformation of nuclei that occurs spontaneously. The nucleus undergoing radioactive decay is called the mother nucleus; the resulting daughter nucleus, as a rule, turns out to be excited, and its transition to the ground state is accompanied by the emission of a γ photon. That. Gamma radiation is the main form of reducing the energy of excited products of radioactive transformations.

Alpha decay. β-rays are a flux of helium He nuclei. Alpha decay is accompanied by the departure of an alpha particle (He) from the nucleus, which initially transforms into the nucleus of an atom of a new chemical element, the charge of which is 2 less and the mass number is 4 units less.

The speeds at which α-particles (i.e., He nuclei) fly out of the decaying nucleus are very high (~106 m/s).

Flying through matter, an α-particle gradually loses its energy, spending it on ionizing the molecules of the substance, and eventually stops. An alpha particle forms approximately 106 pairs of ions on its path per 1 cm of path.

The greater the density of the substance, the shorter the range of α-particles before stopping. In air at normal pressure, the range is several cm, in water, in human tissues (muscles, blood, lymph) 0.1-0.15 mm. α-particles are completely blocked by a regular piece of paper.

α-particles are not very dangerous in case of external irradiation, because may be delayed by clothing and rubber. But α-particles are very dangerous when they enter the human body, due to the high density of ionization they produce. Damage occurring in tissues is not reversible.

Beta decay comes in three varieties. The first - the nucleus, which has undergone a transformation, emits an electron, the second - a positron, the third - is called electron capture (e-capture), the nucleus absorbs one of the electrons.

The third type of decay (electron capture) is when a nucleus absorbs one of the electrons of its atom, as a result of which one of the protons turns into a neutron, emitting a neutrino:

The speed of movement of β-particles in a vacuum is 0.3 – 0.99 the speed of light. They are faster than alpha particles, fly through oncoming atoms and interact with them. β-particles have a lesser ionization effect (50-100 pairs of ions per 1 cm of path in the air) and when a β-particle enters the body, they are less dangerous than α-particles. However, the penetrating ability of β-particles is high (from 10 cm to 25 m and up to 17.5 mm in biological tissues).

Gamma radiation is electromagnetic radiation emitted by atomic nuclei during radioactive transformations, which propagates in a vacuum at a constant speed of 300,000 km/s. This radiation usually accompanies β-decay and, less frequently, α-decay.

γ-rays are similar to X-rays, but have much higher energy (at a shorter wavelength). γ-rays, being electrically neutral, are not deflected in magnetic and electric fields. In matter and vacuum, they propagate rectilinearly and evenly in all directions from the source, without causing direct ionization; when moving in the medium, they knock out electrons, transferring to them part or all of their energy, which produce the ionization process. For 1 cm of travel, γ-rays form 1-2 pairs of ions. In the air they travel from several hundred meters and even kilometers, in concrete - 25 cm, in lead - up to 5 cm, in water - tens of meters, and they penetrate through living organisms.

γ-rays pose a significant danger to living organisms as a source of external radiation.