About types of radiation, its impact on various objects and prospects for application

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After the accidents at the Chernobyl nuclear power plant and the Fukushima-1 nuclear power plant, humanity finally realized how dangerous it is to work with radionuclides. However, physicist Georgy Tikhomirov believes that the experience accumulated by people today allows us to minimize the harm from interaction with ionizing radiation, and radiation can bring us more benefit than harm. He told PostNauka about the types of ionizing radiation, the effect of radiation on living and inanimate objects, and the prospects for the use of ionizing radiation in industrial technologies.

This is material from the “Radiation and Matter” guide dedicated to the 75th anniversary of the nuclear industry. The guide's partner is Rosatom.

Types and what electromagnetic radiation consists of

There are several varieties of it:

• Visible light . This is radiation that can be perceived by human vision. The wavelength is quite short and varies between 380-780 nanometers.
• Infrared . It is something between light radiation and radio waves.
• Radio waves . They are distinguished by their greatest length and accommodate all types of radiation, the waves of which are characterized by a length of half a millimeter.
• Ultraviolet . Radiation that is harmful to a living organism.
• X-ray . It is produced by electronic particles and is widely used in medicine.
• Gamma radiation . It has the shortest wavelength, presenting a high level of danger to the human body.

The characteristics of any electromagnetic wave are made up of three main parameters:

• Frequency . Expresses the number of wave crests passing during one second. The unit of measurement is hertz.
• Polarization . Describes the oscillations of electromagnetic waves in the transverse direction. Radiation becomes polarized when wave oscillations occur in one plane. In practice, this phenomenon can be found in cinemas during 3D screenings. Polarization in 3D glasses separates the image.
• Length . Represents the distance connecting points of electromagnetic radiation that oscillate within the same phase.

The propagation of electromagnetic radiation is possible in any medium, from dense matter to vacuum. In this case, the speed of wave propagation in vacuum space reaches 300 thousand km per second. For example, sound waves do not propagate in a vacuum.

Operating principle

Electromagnetic radiation has energy, the main characteristic of which is its intensity. There is a constant and variable field of electromagnetic waves.

The first is characterized by tension, which is determined by the force exerting a catalytic effect on the current conductor. The unit of voltage is ampere. The alternating variety combines the magnetic and electric varieties of magnetic fields, which expand in space in the form of waves.

The distribution area includes three zones:

Properties

It is known that electromagnetic waves are characterized by certain properties that Maxwell first spoke about. These properties are due to differences and dependence on the length parameter. It is in accordance with these parameters that waves of electromagnetic fields are divided into ranges, which, in turn, have a fairly conventional scale, since adjacent frequencies superimpose their properties on each other.

These include:

• High penetrating ability.
• Fast dissolution rate in the substance.
• Negative and beneficial effects on humans.

Application and influence

Electromagnetic radiation became widely used only at the end of the 19th century, when radio communications were actively developing, through which communication over long distances became possible.

The main electromagnetic sources are large industrial facilities, as well as various electrical transmission lines. In addition, the type of radiation in question has been actively used in the military sphere. There they are represented by radars and other electrical devices that have a complex structure.

In the medical field, infrared radiation is used to treat various diseases. Besides:

• Through X-ray examination, it becomes possible to detect internal damage in the human body.
• The laser allows you to perform operations that require pinpoint precision, etc.

How is laser produced?

The artificial process includes the following:

• Source of energy.
• Active environment.
• Optical cavity.

The active medium absorbs energy from a source, stores it, and releases it as light. Some of this light triggers other atoms to release their energy, so more light is added to what was launched. Mirrors at the end of the optical cavity reflect the light back into the active medium, and the process begins again, causing the light to amplify and causing part of it to form a narrow beam - a laser. To increase light emission, there must be more atoms in the excited state than there were initially. This is called data inversion. This condition does not occur under normal conditions. Therefore, this process should be helped by artificial technologies, not nature.

What is electromagnetic radiation

Electromagnetic radiation is electromagnetic waves propagating in space, emitted by various objects.

Wave nature of radiation

Electromagnetic interaction between objects is subject to electromagnetic theory based on Maxwell's equations. He suggested that the electric and magnetic fields have closed lines of force—strength vectors that oscillate perpendicular to the direction of wave propagation. These waves propagating in space create an electromagnetic field. Later, their existence and wave nature were proven experimentally.

An electromagnetic wave is an electric and magnetic field that mutually transforms into each other.

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Cause of EM Radiation

Electric fields arise when electrical voltages differ, for example, when charged particles appear in the atmosphere during a thunderstorm. Magnetic fields arise around moving charges, which excite a vortex electric field.

Types of electromagnetic radiation, their characteristics

All types of electromagnetic waves travel in a vacuum at the same speed. But their frequency, as well as the length that depends on it, varies, which affects their interaction with different substances. Therefore, the main classification of electromagnetic radiation divides them according to frequency ranges.

Electromagnetic radiation also differs in origin:

With the emergence of a large number of anthropogenic sources of radiation, they began to be classified not only by frequency and wavelength, but also by the degree of their harm to humans. Ionizing radiation can cause reactive changes in the human body, called radiation sickness. Charged particles emit so much energy that they break the bonds between the molecules of the irradiated object. Ionizing radiation includes x-rays and gamma radiation, although atoms can also be affected by other types of electromagnetic waves.

Visible light

Visible light consists of rays of seven primary colors: red, orange, yellow, green, blue, indigo, violet. Each color has its own wavelength.

It is impossible to indicate the exact boundaries of the visible radiation range, since the decrease in sensitivity with distance from the maximum point in the green part of the spectrum occurs gradually. Visible radiation usually has a complex spectral composition, which may include ultraviolet and infrared waves. Shades other than the seven primary colors, such as pink or beige, are formed by mixing monochromatic radiation.

Infrared

Infrared radiation occupies the region of the spectrum between visible light and microwave radiation. The higher the temperature of the emitting body, the more intense the radiation and the shorter the wavelength. To register it, thermal and photoelectric receivers are used. Half of the sun's radiation consists of infrared waves.

The spectrum of this type of radiation includes:

• near-infrared light, 0.75–1.4 µm;
• shortwave, 1.4–3 µm;
• medium wave, 3–8 µm;
• long wavelength, 8–15 µm;
• far, 15–1000 µm.

Radio waves

Radio waves are low-frequency electromagnetic waves - up to 3 THz. They are usually classified by wavelength:

• extra-long, more than 10 km;
• long, 10 km - 1 km;
• medium, 1 km - 100 m;
• short, 100 m - 10 m;
• ultra-short, 10 m - 0.1 mm.

Radio waves can also be divided into amplitude modulated (AM) and frequency modulated (FM). FM radio signals transmit sound by varying the frequency of the carrier wave, rather than its amplitude, like AM signals. The transmission distance of FM signals is much shorter, but the quality of the transmitted sound is higher and they are less susceptible to electromagnetic interference.

Ultraviolet

Ultraviolet radiation occupies the region of the spectrum between visible and x-ray radiation. This is natural radiation from the Sun, which is divided into three spectral regions, focusing on the different biological effects of ultraviolet waves:

• near ultraviolet, UVA, 315–400 nm;
• UV-B, 280–315 nm;
• far ultraviolet, UV-C, 100–280 nm.

Solar radiation reaching the Earth's surface consists of near-ultraviolet rays and a small amount of UV-B rays. UV-C rays are absorbed by the atmosphere.

X-ray

X-ray radiation occupies the range between ultraviolet and gamma radiation: \(0.005–100\) nm, \(2\times10^ - 6\times10^\) Hz. It occurs when electrons collide with the anode surface at high speed, when the anode atoms change their internal structure. The radiation frequency depends on the anode material; it is divided into soft, with a longer wavelength and lower frequency of radiation, and hard.

Radiophobia

Radiation surrounds us. But there is no need to measure it without being involved in working with radioactive sources. Today, a powerful global system of radioactive monitoring has been built, international organizations assess the danger of nuclides and recommend radiation safety standards to similar organizations within countries. All establishments where radioactive sources are used follow rules to prevent harm to workers and the environment.

Surprisingly, to some extent, the consequences of radiation exposure on a person depend on his psychotype and how he perceives increased doses. It was noted that with the same dose of radiation received, people react to it differently and often fear of radiation and stress affect a person much worse than radiation itself. Therefore, it is always necessary to soberly assess the risks and not panic. There are many myths around radiation, but excess background radiation even several times cannot affect the quality of life. The human body has a powerful reserve of protection against radiation exposure, because it exists in nature. There is even an effect of radiation hormesis (however, not recognized by all doctors), as a result of which the body, on the contrary, mobilizes, improving its protective characteristics.

The main source of radiophobia is the media writing about disasters that occurred due to the use of ionizing radiation. After the Chernobyl accident, the press wrote about billions of deaths and genetic consequences in five generations. But all this has little relation to reality - unlike specific studies, in particular the work of Japanese scientists monitoring people irradiated in Hiroshima and Nagasaki, or the work of European, Russian and Ukrainian scientists who are still studying the effects of radiation in the Chernobyl footprint zone . Everything turned out to be not as scary as it was described in the media, and after Chernobyl and Fukushima there was a powerful renaissance of nuclear energy.

EM radiation ranges

The two main parameters of electromagnetic radiation - the oscillation frequency \(f\) (the number of complete oscillation cycles per second) and the wavelength lambda (the distance it travels in one oscillation) - are strictly interconnected. Knowing the frequency of radiation, you can determine its wavelength, and vice versa, by substituting the known value into the expression \(с\;=\;F\times\lambda\), where \(с\) is the speed of light.

The frequencies and lengths of electromagnetic waves vary over a very wide range: from several vibrations per second to \(10^\), from sizes comparable to the sizes of atoms, to millions of kilometers in airless space. Therefore, electromagnetic radiation is usually divided into frequency ranges in order of increasing wavelength, from gamma rays to radio waves. The boundaries between the selected ranges are arbitrary.

Medicine

The use of visible radiation in medicine is common. Lasers are used in microsurgical procedures such as making small, precise incisions, liver surgery, and capillary surgery, which result in little blood loss. Lasers are also used in ophthalmology (cataract removal and vision correction), dermatology (tattoo and scar removal), dentistry (cavity cleaning), and oncology (skin cancer treatment).

What is an example of the use of visible radiation in medicine? Light therapy is also used to relieve seasonal affective disorder, regulate your internal body clock (circadian rhythm) and affect your mood. The therapeutic applications of light and color are also being researched in many hospitals and research centers around the world. The results so far indicate that full spectrum, ultraviolet, color and laser light may have therapeutic benefits for a range of conditions, from chronic pain and depression to immune disorders.

Sources

Regardless of the design of the source of electromagnetic radiation, it is always excited by electric charges that change their speed. Sources can be divided into two types - microscopic and macroscopic.

Microscopic

Charged particles move between energy levels within atoms and molecules. Microscopic sources emit high-frequency radiation: gamma radiation, x-rays, ultraviolet, infrared, visible light. Their properties are the subject of study in nuclear physics and optics.

Macroscopic

In macroscopic sources, electromagnetic radiation is emitted by free electrons of conductors performing synchronous periodic oscillations. Their behavior obeys the laws of classical electrodynamics.

Examples of EM radiation sources

Ultra-long natural radio waves are emitted by astronomical objects. The sun emits visible light, infrared and ultraviolet rays, the Earth's surface and clouds release the absorbed energy into the atmosphere in the form of infrared radiation.

Artificial radiation is generated by radio and television broadcasting and mobile communications towers. When current passes through power lines, parasitic radiation of electromagnetic waves occurs. Also, stray radiation can be created by power distribution systems and current-carrying elements of operating electrical installations: generators, transformers, electromagnets. The degree of danger for a person located in the area of ​​the field depends on the power of its source.

Practical application of electromagnetic waves

Cosmic radio emission is recorded using special telescopes in order to determine the coordinates of celestial bodies, structure, radiation intensity and other characteristics based on the data obtained. Astronomers send sounding radio signals and record their echoes, exploring the planets of the solar system, their satellites and rings, asteroids, comets, and space debris.

Thanks to radio waves, mobile communications, radio communications, radio broadcasting, television broadcasting, and satellite communications operate. The use of infrared emitters for heating rooms and drying painted surfaces speeds up the process and reduces energy costs. Infrared channels for receiving and transmitting data are insensitive to electromagnetic interference, which makes it possible to use infrared waves in conditions where radio communication is difficult. Ultraviolet radiation effectively disinfects air and water, and is also used to dry dental fillings.

X-rays help to obtain images of human bones and internal organs and highlight defects in rails and welds. At airports, X-ray television introscopes are used for contactless viewing of the contents of luggage.

Source

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 6000 K, so its maximum radiation occurs at a wavelength of 475 nm, that is, it lies within the visible spectrum.

The sun heats up the planets around it and their satellites, which also begin to glow. Here it is necessary to distinguish between reflected light and thermal radiation. Thus, our Earth can be seen from space in the form of a blue ball precisely due to reflected sunlight. If we talk about the thermal radiation of the planet, then it also occurs, 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 found in insect cells). This phenomenon is called bioluminescence.