Ust-Kamenogorsk College of Construction

Development of a lesson in physics.

Topic: "Infrared, ultraviolet, x-ray radiation"

Lecturer: O.N. Chirtsova

Ust-Kamenogorsk, 2014

Lesson on the topic "Infrared, ultraviolet, x-rays."

Goals:1) know what infrared, ultraviolet, x-ray radiation is; be able to solve logical problems on the application of these concepts.

2) development of logical thinking, observation, PMD (analysis, synthesis, comparison), skills of working on a concept (its lexical meaning), speech, OUUN (independent work with a source of information, building a table).

3) the formation of a scientific outlook (practical significance of the material being studied, connection with the profession), responsibility, independence, the need to lead a healthy lifestyle, comply with TB standards in professional activities.

Lesson type: learning new material

Type of lesson: theoretical study

Equipment: laptops, projector, presentation, welder's overalls

Literature: Krongart B.A. "Physics-11", INTERNET materials

During the classes.

Organization of students for class.

Preparing for perception.

I draw students' attention to the welder's overalls hanging in front of them, build a conversation on the following questions:

1) What material is the workwear made from? (rubberized fabric, suede) Why from these materials? (I lead students to the answer “protection from thermal (infrared) radiation)”

2) What is the mask for? (UV protection).

3) The main result in the work of the welder? (seam quality) How can the quality of the weld be examined? (one of the methods is x-ray flaw detection). On the slide I show a photo of the x-ray unit and briefly explain the method.

I announce the topic of the lesson (write in a notebook).

Students formulate the purpose of the lesson.

I set tasks for the students for the lesson:

1) Get acquainted with the general characteristics of radiation (according to the position on the scale of electromagnetic radiation).

2) Get acquainted with the general characteristics of each type of radiation.

3) Investigate in detail each type of radiation.

Learning new material.

1. We carry out the first task of the lesson - we get acquainted with the general characteristics of radiation.

On the slide "Scale of electromagnetic radiation". We determine the position of each type of radiation on the scale, analyze the lexical meaning of the words "infrared", "ultraviolet", "X-ray". I support with examples.

1. So, we have completed the first task of the lesson, we move on to the second task - we get acquainted with the general characteristics of each type of radiation. (I show videos about each type of radiation. After watching, I build a short conversation on the content of the videos).

   So, let's move on to the third task of the lesson - the study of each type of radiation.

Students independently perform research work (using a digital source of information, fill out a table). I announce evaluation criteria, regulations. I advise and explain the issues that have arisen in the course of work.

At the end of the work, we listen to the answers of three students, review the answers.

Anchoring.

Orally we solve logical problems:

1. Why is it necessary to wear dark glasses high in the mountains?

2. What kind of radiation is used for drying fruits and vegetables?

Why does a welder wear a mask while welding? protective suit?

Why is barium porridge given to a patient before X-ray examination?

Why do the radiologist (as well as the patient) wear lead aprons?

An occupational disease of welders is cataract (clouding of the lens of the eye). What causes it? (long-term thermal IR radiation) How to avoid?

Electrophthalmia is an eye disease (accompanied by acute pain, pain in the eyes, lacrimation, eyelid spasms). The cause of this disease? (action of UV radiation). How to avoid?

Reflection.

Students answer the following questions in writing:

1. What was the purpose of the lesson?

   Where are the studied types of radiation used?

   What harm can they do?

   Where will the knowledge acquired in the lesson be useful in your profession?

Orally we discuss the answers to these questions, the sheets are handed over.

Homework

Prepare a report on the practical application of IR, UV, X-rays (optional).

Summary of the lesson.

Students hand over notebooks.

I announce grades for the lesson.

Handout.

Infrared radiation.

Infrared radiation - electromagnetic radiation occupying the spectral region between the red end of visible light and microwave radiation.

The optical properties of substances in infrared radiation differ significantly from their properties in visible radiation. For example, a water layer of several centimeters is opaque to infrared radiation with λ = 1 µm. Infrared radiation makes up most of the radiationincandescent lamps, gas discharge lamps, about 50% of solar radiation; infrared radiation emitted by some lasers. To register it, they use thermal and photoelectric receivers, as well as special photographic materials.

The entire range of infrared radiation is divided into three components:

shortwave region: λ = 0.74-2.5 µm;

medium wave region: λ = 2.5-50 µm;

longwave region: λ = 50-2000 µm.

The long-wave edge of this range is sometimes distinguished into a separate range of electromagnetic waves - terahertz radiation (submillimeter radiation).

Infrared radiation is also called "thermal" radiation, since infrared radiation from heated objects is perceived by the human skin as a sensation of warmth. In this case, the wavelengths emitted by the body depend on the heating temperature: the higher the temperature, the shorter the wavelength and the higher the radiation intensity. The emission spectrum of an absolutely black body at relatively low (up to several thousand Kelvin) temperatures lies mainly in this range. Infrared radiation is emitted by excited atoms or ions.

Application.

Night-vision device.

A vacuum photoelectronic device for converting an image of an object invisible to the eye (in the infrared, ultraviolet or X-ray spectrum) into a visible one or to enhance the brightness of the visible image.

Thermography.

Infrared thermography, thermal image or thermal video is a scientific method for obtaining a thermogram - an image in infrared rays that shows a picture of the distribution of temperature fields. Thermographic cameras or thermal imagers detect radiation in the infrared range of the electromagnetic spectrum (approximately 900-14000 nanometers or 0.9-14 µm) and, based on this radiation, create images that allow you to determine overheated or supercooled places. Since infrared radiation is emitted by all objects that have a temperature, according to Planck's formula for blackbody radiation, thermography allows one to "see" the environment with or without visible light. The amount of radiation emitted by an object increases as its temperature rises, so thermography allows us to see differences in temperature. When we look through a thermal imager, warm objects are seen better than those cooled to ambient temperature; humans and warm-blooded animals are more easily visible in the environment, both during the day and at night. As a result, the promotion of the use of thermography can be attributed to the military and security services.

Infrared homing.

Infrared homing head - a homing head that works on the principle of capturing infrared waves emitted by a captured target. It is an optical-electronic device designed to identify a target against the surrounding background and issue a capture signal to an automatic sighting device (APU), as well as to measure and issue a signal of the angular velocity of the line of sight to the autopilot.

Infrared heater.

A heating device that gives off heat to the environment through infrared radiation. In everyday life, it is sometimes inaccurately called a reflector. Radiant energy is absorbed by the surrounding surfaces, turning into thermal energy, heats them, which in turn give off heat to the air. This gives a significant economic effect compared to convection heating, where heat is significantly spent on heating the unused subceiling space. In addition, with the help of IR heaters, it becomes possible to heat locally only those areas in the room where it is necessary without heating the entire volume of the room; the thermal effect of infrared heaters is felt immediately after switching on, which avoids preheating the room. These factors reduce energy costs.

Infrared astronomy.

Branch of astronomy and astrophysics that studies space objects visible in infrared radiation. In this case, infrared radiation means electromagnetic waves with a wavelength from 0.74 to 2000 microns. Infrared radiation is in the range between visible radiation, whose wavelength ranges from 380 to 750 nanometers, and submillimeter radiation.

Infrared astronomy began to develop in the 1830s, several decades after the discovery of infrared radiation by William Herschel. Initially, little progress was made, and until the early 20th century there were no discoveries of astronomical objects in the infrared beyond the Sun and Moon, but after a series of discoveries made in radio astronomy in the 1950s and 1960s, astronomers became aware of the existence of a large amount of information outside the visible range. waves. Since then, modern infrared astronomy has been formed.

infrared spectroscopy.

Infrared spectroscopy - a branch of spectroscopy covering the long wavelength region of the spectrum (> 730 nm beyond the red limit of visible light). Infrared spectra arise as a result of the vibrational (partly rotational) motion of molecules, namely, as a result of transitions between vibrational levels of the ground electronic state of molecules. IR radiation is absorbed by many gases, with the exception of such as O2, N2, H2, Cl2 and monatomic gases. Absorption occurs at a wavelength characteristic of each specific gas, for CO, for example, this is the wavelength of 4.7 microns.

Using infrared absorption spectra, one can establish the structure of molecules of various organic (and inorganic) substances with relatively short molecules: antibiotics, enzymes, alkaloids, polymers, complex compounds, etc. Vibrational spectra of molecules of various organic (and inorganic) substances with relatively long molecules (proteins, fats, carbohydrates, DNA, RNA, etc.) are in the terahertz range, so the structure of these molecules can be established using radio frequency spectrometers in the terahertz range. By the number and position of the peaks in the IR absorption spectra, one can judge the nature of the substance (qualitative analysis), and by the intensity of the absorption bands, the amount of the substance (quantitative analysis). The main instruments are various types of infrared spectrometers.

infrared channel.

An infrared channel is a data transmission channel that does not require wired connections for its operation. In computer technology, it is usually used to connect computers with peripheral devices (IrDA interface). Unlike the radio channel, the infrared channel is insensitive to electromagnetic interference, and this allows it to be used in industrial conditions. The disadvantages of the infrared channel include the high cost of receivers and transmitters, which require the conversion of an electrical signal into infrared and vice versa, as well as low transmission rates (usually does not exceed 5-10 Mbps, but when using infrared lasers, significantly higher speeds are possible). In addition, the confidentiality of the transmitted information is not ensured. In line-of-sight conditions, an infrared channel can provide communication over distances of several kilometers, but it is most convenient for connecting computers located in the same room, where reflections from the walls of the room provide a stable and reliable connection. The most natural type of topology here is the "bus" (that is, the transmitted signal is simultaneously received by all subscribers). It is clear that with so many shortcomings, the infrared channel could not be widely used.

The medicine

Infrared rays are used in physiotherapy.

Remote control

Infrared diodes and photodiodes are widely used in remote controls, automation systems, security systems, some mobile phones (infrared port), etc. Infrared rays do not distract a person's attention due to their invisibility.

Interestingly, the infrared radiation of a household remote control is easily captured using a digital camera.

When painting

Infrared emitters are used in industry for drying paint surfaces. The infrared drying method has significant advantages over the traditional, convection method. First of all, this is, of course, an economic effect. The speed and energy expended with infrared drying is less than those with traditional methods.

Food sterilization

With the help of infrared radiation, food products are sterilized for the purpose of disinfection.

Anti-corrosion agent

Infra-red rays are used to prevent corrosion of varnished surfaces.

food industry

A feature of the use of infrared radiation in the food industry is the possibility of penetration of an electromagnetic wave into such capillary-porous products as grain, cereals, flour, etc. to a depth of up to 7 mm. This value depends on the nature of the surface, structure, properties of the material and the frequency response of the radiation. An electromagnetic wave of a certain frequency range has not only a thermal, but also a biological effect on the product, it helps to accelerate biochemical transformations in biological polymers (starch, protein, lipids). Conveyor drying conveyors can be successfully used when laying grain in granaries and in the flour-grinding industry.

In addition, infrared radiation is widely used forspace heating and streetspaces. Infrared heaters are used to organize additional or main heating in premises (houses, apartments, offices, etc.), as well as for local heating of outdoor space (street cafes, gazebos, verandas).

The disadvantage is the significantly greater non-uniformity of heating, which is completely unacceptable in a number of technological processes.

Checking money for authenticity

The infrared emitter is used in devices for checking money. Applied to the banknote as one of the security elements, special metameric inks can only be seen in the infrared range. Infrared currency detectors are the most error-free devices for checking money for authenticity. Applying infrared tags to banknotes, unlike ultraviolet ones, is expensive for counterfeiters and therefore economically unprofitable. Therefore, banknote detectors with a built-in IR emitter, today, are the most reliable protection against counterfeiting.

Health hazard!!!

Very strong infrared radiation in places of high heat can dry out the mucous membrane of the eyes. It is most dangerous when the radiation is not accompanied by visible light. In such situations, it is necessary to wear special protective goggles for the eyes.

Earth as an infrared emitter

The Earth's surface and clouds absorb visible and invisible radiation from the sun and re-radiate most of the energy in the form of infrared radiation back into the atmosphere. Certain substances in the atmosphere, mainly water droplets and water vapor, but also carbon dioxide, methane, nitrogen, sulfur hexafluoride and chlorofluorocarbons, absorb this infrared radiation and re-radiate it in all directions, including back to Earth. Thus, the greenhouse effect keeps the atmosphere and surface warmer than if there were no infrared absorbers in the atmosphere.

x-ray radiation

X-ray radiation - electromagnetic waves, the photon energy of which lies on the electromagnetic wave scale between ultraviolet radiation and gamma radiation, which corresponds to wavelengths from 10−2 to 102 Å (from 10−12 to 10−8 m)

Laboratory sources

X-ray tubes

X-rays are produced by strong acceleration of charged particles (bremsstrahlung), or by high-energy transitions in the electron shells of atoms or molecules. Both effects are used in X-ray tubes. The main structural elements of such tubes are a metal cathode and an anode (previously also called an anticathode). In x-ray tubes, electrons emitted from the cathode are accelerated by the difference in electrical potential between the anode and cathode (no x-rays are emitted because the acceleration is too low) and hit the anode, where they are abruptly decelerated. In this case, X-ray radiation is generated due to bremsstrahlung, and electrons are simultaneously knocked out of the inner electron shells of the anode atoms. Empty spaces in the shells are occupied by other electrons of the atom. In this case, X-ray radiation is emitted with an energy spectrum characteristic of the anode material (characteristic radiation, frequencies are determined by Moseley's law: where Z is the atomic number of the anode element, A and B are constants for a certain value of the principal quantum number n of the electron shell). At present, anodes are made mainly of ceramics, and the part where the electrons hit is made of molybdenum or copper.

Crookes tube

In the process of acceleration-deceleration, only about 1% of the kinetic energy of an electron goes to X-rays, 99% of the energy is converted into heat.

Particle accelerators

X-rays can also be obtained in particle accelerators. The so-called synchrotron radiation occurs when a beam of particles in a magnetic field is deflected, as a result of which they experience acceleration in a direction perpendicular to their movement. Synchrotron radiation has a continuous spectrum with an upper limit. With appropriately chosen parameters (the magnitude of the magnetic field and the energy of the particles), X-rays can also be obtained in the spectrum of synchrotron radiation.

Biological impact

X-rays are ionizing. It affects the tissues of living organisms and can cause radiation sickness, radiation burns, and malignant tumors. For this reason, protective measures must be taken when working with X-rays. It is believed that the damage is directly proportional to the absorbed dose of radiation. X-ray radiation is a mutagenic factor.

Registration

Luminescence effect. X-rays can cause some substances to glow (fluorescence). This effect is used in medical diagnostics during fluoroscopy (observation of an image on a fluorescent screen) and X-ray photography (radiography). Medical photographic films are usually used in combination with intensifying screens, which include X-ray phosphors, which glow under the action of X-rays and illuminate the light-sensitive photographic emulsion. The method of obtaining a life-size image is called radiography. With fluorography, the image is obtained on a reduced scale. The luminescent substance (scintillator) can be optically connected to an electronic light detector (photomultiplier tube, photodiode, etc.), the resulting device is called a scintillation detector. It allows you to register individual photons and measure their energy, since the energy of a scintillation flash is proportional to the energy of an absorbed photon.

photographic effect. X-rays, as well as ordinary light, are able to directly illuminate the photographic emulsion. However, without the fluorescent layer, this requires 30-100 times the exposure (i.e. dose). This method (known as screenless radiography) has the advantage of sharper images.

In semiconductor detectors, X-rays produce electron-hole pairs in the p-n junction of a diode connected in the blocking direction. In this case, a small current flows, the amplitude of which is proportional to the energy and intensity of the incident X-ray radiation. In the pulsed mode, it is possible to register individual X-ray photons and measure their energy.

Individual X-ray photons can also be registered using gas-filled detectors of ionizing radiation (Geiger counter, proportional chamber, etc.).

Application

With the help of X-rays, it is possible to "enlighten" the human body, as a result of which it is possible to obtain an image of the bones, and in modern instruments, of internal organs (see alsoradiography and fluoroscopy). This uses the fact that the element calcium (Z=20) contained mainly in the bones has an atomic number much larger than the atomic numbers of the elements that make up soft tissues, namely hydrogen (Z=1), carbon (Z=6) , nitrogen (Z=7), oxygen (Z=8). In addition to conventional devices that give a two-dimensional projection of the object under study, there are computed tomographs that allow you to obtain a three-dimensional image of the internal organs.

The detection of defects in products (rails, welds, etc.) using X-rays is calledx-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 analysis). A famous example is the determination of the structure of DNA.

X-rays can be used to determine the chemical composition of a substance. In an electron beam microprobe (or in an electron microscope), the analyzed substance is irradiated with electrons, while the atoms are ionized and emit characteristic X-ray radiation. X-rays can be used instead of electrons. This analytical method is calledX-ray fluorescence analysis.

Airports are actively usingx-ray television introscopes, allowing you to view the contents of hand luggage and baggage in order to visually detect objects that are dangerous on the monitor screen.

X-ray therapy- a section of radiation therapy covering the theory and practice of therapeutic use of x-rays generated at a voltage on an x-ray tube of 20-60 kV and a skin-focal distance of 3-7 cm (short-range radiotherapy) or at a voltage of 180-400 kV and a skin-focal distance of 30 -150 cm (remote radiotherapy). X-ray therapy is carried out mainly with superficially located tumors and with some other diseases, including skin diseases (ultrasoft X-rays of Bucca).

natural x-rays

On Earth, electromagnetic radiation in the X-ray range is formed as a result of ionization of atoms by radiation that occurs during radioactive decay, as a result of the Compton effect of gamma radiation that occurs during nuclear reactions, and also by cosmic radiation. Radioactive decay also leads to direct emission of X-ray quanta if it causes a rearrangement of the electron shell of the decaying atom (for example, during electron capture). X-ray radiation that occurs on other celestial bodies does not reach the Earth's surface, as it is completely absorbed by the atmosphere. It is being explored by satellite X-ray telescopes such as Chandra and XMM-Newton.

One of the main methods of non-destructive testing is the radiographic method of control (RK) -x-ray flaw detection. This type of control is widely used to check the quality of technological pipelines, metal structures, technological equipment, composite materials in various industries and the construction complex. X-ray control is actively used today to detect various defects in welds and joints. The radiographic method of testing welded joints (or X-ray flaw detection) is carried out in accordance with the requirements of GOST 7512-86.

The method is based on the different absorption of X-rays by materials, and the degree of absorption directly depends on the atomic number of the elements and the density of the medium of a particular material. The presence of defects such as cracks, inclusions of foreign materials, slags and pores leads to the fact that X-rays are attenuated to one degree or another. By registering their intensity using X-ray control, it is possible to determine the presence, as well as the location of various material inhomogeneities.

Main features of X-ray control:

The ability to detect such defects that cannot be detected by any other method - for example, non-solders, shells and others;

Possibility of exact localization of the detected defects, which makes it possible to quickly repair;

The possibility of assessing the magnitude of the convexity and concavity of the weld reinforcing beads.

UV radiation

Ultraviolet radiation (ultraviolet rays, UV radiation) - electromagnetic radiation occupying the spectral range between visible and x-ray radiation. Wavelengths of UV radiation lie in the range from 10 to 400 nm (7.5 1014-3 1016 Hz). The term comes from lat. ultra - above, beyond and purple. In colloquial speech, the name "ultraviolet" can also be used.

Impact on human health .

The biological effects of ultraviolet radiation in the three spectral regions are significantly different, so biologists sometimes distinguish the following ranges as the most important in their work:

Near ultraviolet, UV-A rays (UVA, 315-400 nm)

UV-B rays (UVB, 280-315 nm)

Far ultraviolet, UV-C rays (UVC, 100-280nm)

Almost all UVC and approximately 90% UVB are absorbed by ozone, as well as water vapour, oxygen and carbon dioxide as sunlight passes through the earth's atmosphere. Radiation from the UVA range is rather weakly absorbed by the atmosphere. Therefore, the radiation that reaches the Earth's surface contains a large part of the near ultraviolet UVA and a small proportion - UVB.

Somewhat later, in the works (O. G. Gazenko, Yu. E. Nefedov, E. A. Shepelev, S. N. Zaloguev, N. E. Panferova, I. V. Anisimova), the indicated specific effect of radiation was confirmed in space medicine . Prophylactic UV irradiation was introduced into the practice of space flights along with the Guidelines (MU) 1989 "Prophylactic ultraviolet irradiation of people (using artificial sources of UV radiation)" . Both documents are a reliable basis for further improvement of UV prevention.

Action on the skin

Skin exposure to ultraviolet radiation that exceeds the skin's natural protective ability to tan leads to burns.

Ultraviolet radiation can lead to the formation of mutations (ultraviolet mutagenesis). The formation of mutations, in turn, can cause skin cancer, skin melanoma and premature aging.

Action on the eyes

Ultraviolet radiation of the medium wave range (280-315 nm) is practically imperceptible to the human eye and is mainly absorbed by the corneal epithelium, which, with intense irradiation, causes radiation damage - corneal burns (electrophthalmia). This is manifested by increased lacrimation, photophobia, edema of the corneal epithelium, blepharospasm. As a result of a pronounced reaction of eye tissues to ultraviolet, the deep layers (corneal stroma) are not affected, since the human body reflexively eliminates the effects of ultraviolet radiation on the organs of vision, only the epithelium is affected. After the regeneration of the epithelium, vision, in most cases, is completely restored. Soft long-wave ultraviolet (315-400 nm) is perceived by the retina as a weak violet or grayish-blue light, but is almost completely retained by the lens, especially in middle-aged and elderly people. Patients implanted with early artificial lenses began to see ultraviolet light; modern samples of artificial lenses do not let ultraviolet through. Shortwave ultraviolet (100-280 nm) can penetrate to the retina. Since ultraviolet short-wave radiation is usually accompanied by ultraviolet radiation of other ranges, with intense exposure to the eyes, a corneal burn (electrophthalmia) will occur much earlier, which will exclude the effect of ultraviolet radiation on the retina for the above reasons. In clinical ophthalmological practice, the main type of eye damage caused by ultraviolet radiation is corneal burn (electrophthalmia).

Eye protection

To protect the eyes from the harmful effects of ultraviolet radiation, special goggles are used that block up to 100% of ultraviolet radiation and are transparent in the visible spectrum. As a rule, the lenses of such glasses are made of special plastics or polycarbonate.

Many types of contact lenses also offer 100% UV protection (look at the package label).

Filters for ultraviolet rays are solid, liquid and gaseous. For example, ordinary glass is opaque at λ< 320 нм; в более коротковолновой области прозрачны лишь специальные сорта стекол (до 300-230 нм), кварц прозрачен до 214 нм, флюорит - до 120 нм. Для еще более коротких волн нет подходящего по прозрачности материала для линз объектива и приходится применять отражательную оптику - вогнутые зеркала. Однако для столь короткого ультрафиолета непрозрачен уже и воздух, который заметно поглощает ультрафиолет, начиная с 180 нм.

UV Sources

natural springs

The main source of ultraviolet radiation on Earth is the Sun. The ratio of UV-A to UV-B radiation intensity, the total amount of ultraviolet rays reaching the Earth's surface, depends on the following factors:

on the concentration of atmospheric ozone above the earth's surface (see ozone holes)

from the height of the sun above the horizon

from height above sea level

from atmospheric dispersion

from cloud cover

on the degree of reflection of UV rays from the surface (water, soil)

Two ultraviolet fluorescent lamps, both lamps emit "long wavelength" (UV-A) wavelengths ranging from 350 to 370 nm

A DRL lamp without a bulb is a powerful source of ultraviolet radiation. Hazardous to eyes and skin during operation.

artificial sources

Thanks to the creation and improvement of artificial sources of UV radiation, which went in parallel with the development of electric sources of visible light, today specialists working with UV radiation in medicine, preventive, sanitary and hygienic institutions, agriculture, etc., are provided with significantly greater opportunities than with using natural UV radiation. The development and production of UV lamps for photobiological installations (UFBD) is currently carried out by a number of major electric lamp companies and others. Unlike lighting sources, UV radiation sources, as a rule, have a selective spectrum, designed to achieve the maximum possible effect for a particular FB process. Classification of artificial UV IS by areas of application, determined through the action spectra of the corresponding FB processes with certain UV spectral ranges:

Erythema lamps were developed in the 60s of the last century to compensate for the “UV deficiency” of natural radiation and, in particular, to intensify the process of photochemical synthesis of vitamin D3 in human skin (“anti-rachitis effect”).

In the 1970s and 1980s, erythema LLs, apart from medical institutions, were used in special “fotaria” (for example, for miners and mountain workers), in separate public and industrial buildings in the northern regions, and also for irradiating young farm animals.

The LE30 spectrum is radically different from the solar spectrum; region B accounts for most of the radiation in the UV region, radiation with a wavelength λ< 300нм, которое в естественных условиях вообще отсутствует, может достигать 20 % от общего УФ излучения. Обладая хорошим «антирахитным действием», излучение эритемных ламп с максимумом в диапазоне 305-315 нм оказывает одновременно сильное повреждающее воздействие на коньюктиву (слизистую оболочку глаза). Отметим, что в номенклатуре УФ ИИ фирмы Philips присутствуют ЛЛ типа TL12 с предельно близкими к ЛЭ30 спектральными характеристиками, которые наряду с более «жесткой» УФ ЛЛ типа TL01 используются в медицине для лечения фотодерматозов. Диапазон существующих УФ ИИ, которые используются в фототерапевтических установках, достаточно велик; наряду с указанными выше УФ ЛЛ, это лампы типа ДРТ или специальные МГЛ зарубежного производства, но с обязательной фильтрацией УФС излучения и ограничением доли УФВ либо путем легирования кварца, либо с помощью специальных светофильтров, входящих в комплект облучателя.

In the countries of Central and Northern Europe, as well as in Russia, UV DUs of the “Artificial solarium” type, which use UV LL, which cause a fairly rapid formation of a tan, are widely used. In the spectrum of "tanning" UV LL, "soft" radiation in the UVA zone predominates. The share of UVB is strictly regulated, depends on the type of installations and skin type (in Europe, there are 4 types of human skin from "Celtic" to "Mediterranean") and is 1-5% from total UV radiation. LLs for tanning are available in standard and compact versions with power from 15 to 160 W and length from 30 to 180 cm.

In 1980, the American psychiatrist Alfred Levy described the effect of "winter depression", which is now classified as a disease and is abbreviated as SAD (Seasonal Affective Disorder - Seasonal Affective Disorder). The disease is associated with insufficient insolation, that is, natural light. According to experts, ~ 10-12% of the world's population is affected by SAD syndrome, and primarily residents of the countries of the Northern Hemisphere. Data for the USA are known: in New York - 17%, in Alaska - 28%, even in Florida - 4%. For the Nordic countries, data range from 10 to 40%.

Due to the fact that SAD is undoubtedly one of the manifestations of "solar failure", a return of interest to the so-called "full spectrum" lamps is inevitable, which accurately reproduces the spectrum of natural light not only in the visible, but also in the UV region. A number of foreign companies have included full-spectrum LLs in their product range, for example, Osram and Radium companies produce similar UV IRs with a power of 18, 36, and 58 W under the names, respectively, "Biolux" and "Biosun", the spectral characteristics of which practically coincide. These lamps, of course, do not have an "anti-rachitic effect", but they help to eliminate a number of adverse syndromes in people associated with poor health in the autumn-winter period and can also be used for preventive purposes in educational institutions, schools, kindergartens, enterprises and institutions to compensate " light starvation. At the same time, it should be recalled that LLs of the "full spectrum" compared to LLs of the color LB have a luminous efficiency of about 30% less, which will inevitably lead to an increase in energy and capital costs in the lighting and irradiation installation. Such installations must be designed and operated in accordance with the requirements of CTES 009/E:2002 "Photobiological safety of lamps and lamp systems".

A very rational application was found for UFLL, the emission spectrum of which coincides with the phototaxis action spectrum of some types of flying insect pests (flies, mosquitoes, moths, etc.), which can be carriers of diseases and infections, lead to spoilage of products and products.

These UV LLs are used as attractant lamps in special light traps installed in cafes, restaurants, food industry enterprises, livestock and poultry farms, clothing warehouses, etc.

Mercury-quartz lamp

Fluorescent lamps "daylight" (have a small UV component from the mercury spectrum)

Excilamp

Light-emitting diode

Electric arc ionization process (In particular, the process of welding metals)

Laser sources

There are a number of lasers operating in the ultraviolet region. The laser makes it possible to obtain coherent radiation of high intensity. However, the ultraviolet region is difficult for laser generation, so there are no sources as powerful here as in the visible and infrared ranges. Ultraviolet lasers find their application in mass spectrometry, laser microdissection, biotechnology and other scientific research, in eye microsurgery (LASIK), for laser ablation.

As an active medium in ultraviolet lasers, either gases (for example, an argon laser, a nitrogen laser, an excimer laser, etc.), condensed inert gases, special crystals, organic scintillators, or free electrons propagating in an undulator can be used.

There are also ultraviolet lasers that use the effects of non-linear optics to generate the second or third harmonic in the ultraviolet range.

In 2010, a free electron laser was demonstrated for the first time, generating coherent photons with an energy of 10 eV (the corresponding wavelength is 124 nm), that is, in the vacuum ultraviolet range.

Degradation of polymers and dyes

Many polymers used in consumer products degrade when exposed to UV light. To prevent degradation, special substances capable of absorbing UV are added to such polymers, which is especially important when the product is exposed to direct sunlight. The problem manifests itself in the disappearance of color, tarnishing of the surface, cracking, and sometimes the complete destruction of the product itself. The rate of destruction increases with increasing time of exposure and intensity of sunlight.

The described effect is known as UV aging and is one of the varieties of polymer aging. Sensitive polymers include thermoplastics such as polypropylene, polyethylene, polymethyl methacrylate (organic glass) as well as special fibers such as aramid fiber. UV absorption leads to the destruction of the polymer chain and loss of strength at a number of points in the structure. The action of UV on polymers is used in nanotechnologies, transplantation, X-ray lithography, and other areas to modify the properties (roughness, hydrophobicity) of the surface of polymers. For example, the smoothing effect of vacuum ultraviolet (VUV) on the surface of polymethyl methacrylate is known.

Scope of application

Black light

A soaring dove appears on VISA credit cards under UV light

A black light lamp is a lamp that emits predominantly in the long wavelength ultraviolet region of the spectrum (UVA range) and produces very little visible light.

To protect documents from counterfeiting, they are often provided with UV labels that are only visible under UV light conditions. Most passports, as well as banknotes of various countries, contain security elements in the form of paint or threads that glow in ultraviolet light.

The ultraviolet radiation given by black light lamps is quite mild and has the least serious negative impact on human health. However, when using these lamps in a dark room, there is some danger associated precisely with insignificant radiation in the visible spectrum. This is due to the fact that in the dark the pupil expands and a relatively large part of the radiation freely enters the retina.

Sterilization by ultraviolet radiation

Disinfection of air and surfaces

Quartz lamp used for sterilization in the laboratory

Ultraviolet lamps are used for sterilization (disinfection) of water, air and various surfaces in all spheres of human activity. In the most common low-pressure lamps, almost the entire emission spectrum falls at a wavelength of 253.7 nm, which is in good agreement with the peak of the bactericidal efficacy curve (that is, the efficiency of absorption of ultraviolet light by DNA molecules). This peak is located around the 253.7 nm wavelength, which has the greatest effect on DNA, but natural substances (eg water) delay UV penetration.

Germicidal UV radiation at these wavelengths causes dimerization of thymine in DNA molecules. The accumulation of such changes in the DNA of microorganisms leads to a slowdown in their reproduction and extinction. Germicidal ultraviolet lamps are mainly used in devices such as germicidal irradiators and germicidal recirculators.

Ultraviolet treatment of water, air and surfaces does not have a prolonged effect. The advantage of this feature is that harmful effects on humans and animals are excluded. In the case of wastewater treatment with UV, the flora of water bodies is not affected by discharges, as, for example, with the discharge of water treated with chlorine, which continues to destroy life long after use in the treatment plant.

Ultraviolet lamps with a bactericidal effect in everyday life are often referred to simply as bactericidal lamps. Quartz lamps also have a bactericidal effect, but their name is not due to the effect of action, as in bactericidal lamps, but is associated with the material of the lamp bulb - quartz glass.

Drinking water disinfection

Disinfection of water is carried out by the method of chlorination in combination, as a rule, with ozonation or disinfection with ultraviolet (UV) radiation. Ultraviolet (UV) disinfection is a safe, economical and effective method of disinfection. Neither ozonation nor ultraviolet radiation has a bactericidal aftereffect, therefore they are not allowed to be used as independent means of water disinfection in the preparation of water for drinking water supply, for swimming pools. Ozonation and ultraviolet disinfection are used as additional disinfection methods, together with chlorination, increase the efficiency of chlorination and reduce the amount of added chlorine-containing reagents.

The principle of operation of UV radiation. UV disinfection is performed by irradiating microorganisms in water with UV radiation of a certain intensity (a sufficient wavelength for the complete destruction of microorganisms is 260.5 nm) for a certain period of time. As a result of such irradiation, microorganisms "microbiologically" die, as they lose their ability to reproduce. UV radiation in the wavelength range of about 254 nm penetrates well through water and the cell wall of a water-borne microorganism and is absorbed by the DNA of microorganisms, causing damage to its structure. As a result, the process of reproduction of microorganisms stops. It should be noted that this mechanism extends to living cells of any organism as a whole, and this is precisely what causes the danger of hard ultraviolet radiation.

Although UV treatment is several times inferior to ozonation in terms of the effectiveness of water disinfection, today the use of UV radiation is one of the most effective and safe methods of water disinfection in cases where the volume of treated water is small.

Currently, in developing countries, in regions experiencing a lack of clean drinking water, the method of water disinfection by sunlight (SODIS) is being introduced, in which the ultraviolet component of solar radiation plays the main role in purifying water from microorganisms.

Chemical analysis

UV spectrometry

UV spectrophotometry is based on irradiating a substance with monochromatic UV radiation, the wavelength of which changes with time. The substance absorbs UV radiation with different wavelengths to varying degrees. The graph, on the y-axis of which the amount of transmitted or reflected radiation is plotted, and on the abscissa - the wavelength, forms a spectrum. The spectra are unique for each substance; this is the basis for the identification of individual substances in a mixture, as well as their quantitative measurement.

Mineral analysis

Many minerals contain substances that, when illuminated with ultraviolet radiation, begin to emit visible light. Each impurity glows in its own way, which makes it possible to determine the composition of a given mineral by the nature of the glow. A. A. Malakhov in his book “Interesting about Geology” (M., “Molodaya Gvardiya”, 1969. 240 s) talks about this as follows: “The unusual glow of minerals is caused by cathode, ultraviolet, and x-rays. In the world of dead stone, those minerals light up and shine most brightly, which, having fallen into the zone of ultraviolet light, tell about the smallest impurities of uranium or manganese included in the composition of the rock. Many other minerals that do not contain any impurities also flash with a strange "unearthly" color. I spent the whole day in the laboratory, where I observed the luminescent glow of minerals. Ordinary colorless calcite colored miraculously under the influence of various light sources. Cathode rays made the crystal ruby ​​red, in ultraviolet it lit up crimson red tones. Two minerals - fluorite and zircon - did not differ in x-rays. Both were green. But as soon as the cathode light was turned on, the fluorite turned purple, and the zircon turned lemon yellow.” (p. 11).

Qualitative chromatographic analysis

Chromatograms obtained by TLC are often viewed in ultraviolet light, which makes it possible to identify a number of organic substances by the color of the luminescence and the retention index.

Catching insects

Ultraviolet radiation is often used when catching insects in the light (often in combination with lamps emitting in the visible part of the spectrum). This is due to the fact that in most insects the visible range is shifted, compared to human vision, to the short-wavelength part of the spectrum: insects do not see what a person perceives as red, but they see soft ultraviolet light. Perhaps that is why when welding in argon (with an open arc), flies are fried (they fly into the light and there the temperature is 7000 degrees)!

Oxygen, sunlight and water contained in the Earth's atmosphere are the main conditions conducive to the continuation of life on the planet. Researchers have long proven that the intensity and spectrum of solar radiation in the vacuum that exists in space remains unchanged.

On Earth, the intensity of its impact, which we call ultraviolet radiation, depends on many factors. Among them: the season, the geographical location of the area above sea level, the thickness of the ozone layer, cloudiness, as well as the level of concentration of industrial and natural impurities in the air masses.

Ultra-violet rays

Sunlight reaches us in two ranges. The human eye can only distinguish one of them. Ultraviolet rays are in the spectrum invisible to humans. What are they? It is nothing but electromagnetic waves. The length of ultraviolet radiation is in the range from 7 to 14 nm. Such waves carry huge flows of thermal energy to our planet, which is why they are often called thermal waves.

By ultraviolet radiation it is customary to understand an extensive spectrum consisting of electromagnetic waves with a range conditionally divided into far and near rays. The first of them are considered vacuum. They are completely absorbed by the upper atmosphere. Under the conditions of the Earth, their generation is possible only in the conditions of vacuum chambers.

As for near ultraviolet rays, they are divided into three subgroups, classified by range into:

Long, ranging from 400 to 315 nanometers;

Medium - from 315 to 280 nanometers;

Short - from 280 to 100 nanometers.

Measuring instruments

How does a person determine ultraviolet radiation? To date, there are many special devices designed not only for professional, but also for domestic use. They measure the intensity and frequency, as well as the magnitude of the received dose of UV rays. The results allow us to assess their possible harm to the body.

UV Sources

The main "supplier" of UV rays on our planet is, of course, the Sun. However, to date, artificial sources of ultraviolet radiation have been invented by man, which are special lamp devices. Among them:

High pressure mercury-quartz lamp capable of operating in the general range of 100 to 400 nm;

Fluorescent vital lamp generating wavelengths from 280 to 380 nm, the maximum peak of its radiation is between 310 and 320 nm;

Ozone-free and ozone germicidal lamps that produce ultraviolet rays, 80% of which are 185 nm long.

The benefits of UV rays

Similar to the natural ultraviolet radiation coming from the Sun, the light produced by special devices affects the cells of plants and living organisms, changing their chemical structure. Today, researchers know only a few varieties of bacteria that can exist without these rays. The rest of the organisms, once in conditions where there is no ultraviolet radiation, will certainly die.

UV rays can have a significant impact on ongoing metabolic processes. They increase the synthesis of serotonin and melatonin, which has a positive effect on the work of the central nervous system, as well as the endocrine system. Under the influence of ultraviolet light, the production of vitamin D is activated. And this is the main component that promotes the absorption of calcium and prevents the development of osteoporosis and rickets.

Harm of UV rays

Harsh ultraviolet radiation, detrimental to living organisms, does not let the ozone layers in the stratosphere reach the Earth. However, rays in the middle range, reaching the surface of our planet, can cause:

Ultraviolet erythema - a severe burn of the skin;

Cataract - clouding of the lens of the eye, which leads to blindness;

Melanoma is skin cancer.

In addition, ultraviolet rays can have a mutagenic effect, cause malfunctions in the immune forces, which causes oncological pathologies.

Skin lesion

Ultraviolet rays sometimes cause:

1. Acute skin lesions. Their occurrence is facilitated by high doses of solar radiation containing mid-range rays. They act on the skin for a short time, causing erythema and acute photodermatosis.
2. Delayed skin injury. It occurs after prolonged exposure to long-wave UV rays. These are chronic photodermatitis, solar geroderma, photoaging of the skin, the occurrence of neoplasms, ultraviolet mutagenesis, basal cell and squamous cell skin cancer. This list also includes herpes.

Both acute and delayed damage is sometimes caused by excessive exposure to artificial sunbathing, as well as visits to those tanning salons that use non-certified equipment or where UV lamps are not calibrated.

Skin protection

The human body, with a limited amount of any sunbathing, is able to cope with ultraviolet radiation on its own. The fact is that over 20% of such rays can delay a healthy epidermis. To date, protection from ultraviolet radiation, in order to avoid the occurrence of malignant tumors, will require:

Limiting the time spent in the sun, which is especially important during the summer midday hours;

Wearing light, but at the same time closed clothing;

Selection of effective sunscreens.

Using the bactericidal properties of ultraviolet light

UV rays can kill fungus, as well as other microbes that are on objects, wall surfaces, floors, ceilings and in the air. In medicine, these bactericidal properties of ultraviolet radiation are widely used, and their use is appropriate. Special lamps that produce UV rays ensure the sterility of surgical and manipulation rooms. However, ultraviolet bactericidal radiation is used by doctors not only to combat various nosocomial infections, but also as one of the methods for eliminating many diseases.

Phototherapy

The use of ultraviolet radiation in medicine is one of the methods of getting rid of various diseases. In the process of such treatment, a dosed effect of UV rays on the patient's body is produced. At the same time, the use of ultraviolet radiation in medicine for these purposes becomes possible due to the use of special phototherapy lamps.

A similar procedure is carried out to eliminate diseases of the skin, joints, respiratory organs, peripheral nervous system, and female genital organs. Ultraviolet light is prescribed to accelerate the healing process of wounds and to prevent rickets.

Especially effective is the use of ultraviolet radiation in the treatment of psoriasis, eczema, vitiligo, some types of dermatitis, prurigo, porphyria, pruritis. It is worth noting that this procedure does not require anesthesia and does not cause discomfort to the patient.

The use of a lamp that produces ultraviolet allows you to get a good result in the treatment of patients who have undergone severe purulent operations. In this case, the bactericidal property of these waves also helps patients.

The use of UV rays in cosmetology

Infrared waves are actively used in the field of maintaining human beauty and health. Thus, the use of ultraviolet germicidal radiation is necessary to ensure the sterility of various rooms and devices. For example, it can be the prevention of infection of manicure tools.

The use of ultraviolet radiation in cosmetology is, of course, a solarium. In it, with the help of special lamps, customers can get a tan. It perfectly protects the skin from possible subsequent sunburns. That is why cosmetologists recommend having several sessions in the solarium before traveling to hot countries or to the sea.

Necessary in cosmetology and special UV lamps. Thanks to them, there is a rapid polymerization of a special gel used for manicure.

Determination of electronic structures of objects

Ultraviolet radiation also finds its application in physical research. With its help, the spectra of reflection, absorption and emission in the UV region are determined. This makes it possible to refine the electronic structure of ions, atoms, molecules, and solids.

The UV spectra of stars, the Sun and other planets carry information about the physical processes that occur in the hot regions of the studied space objects.

Water purification

Where else are UV rays used? Ultraviolet bactericidal radiation finds its application for the disinfection of drinking water. And if earlier chlorine was used for this purpose, today its negative effect on the body has already been studied quite well. So, vapors of this substance can cause poisoning. The ingestion of chlorine itself provokes the occurrence of oncological diseases. That is why ultraviolet lamps are increasingly being used to disinfect water in private homes.

UV rays are also used in swimming pools. Ultraviolet emitters to eliminate bacteria are used in the food, chemical and pharmaceutical industries. These areas also need clean water.

Air disinfection

Where else does a person use UV rays? The use of ultraviolet radiation for air disinfection is also becoming more common in recent years. Recirculators and emitters are installed in crowded places, such as supermarkets, airports and train stations. The use of UV radiation, which affects microorganisms, makes it possible to disinfect their habitat to the highest degree, up to 99.9%.

domestic use

Quartz lamps that produce UV rays have been disinfecting and purifying the air in clinics and hospitals for many years. However, in recent years, ultraviolet radiation has been increasingly used in everyday life. It is highly effective in eliminating organic contaminants such as fungus and mold, viruses, yeasts and bacteria. These micro-organisms spread particularly rapidly in rooms where people, for various reasons, tightly close windows and doors for a long time.

The use of a bactericidal irradiator in domestic conditions becomes advisable with a small area of ​​\u200b\u200bhousing and a large family with small children and pets. A UV lamp will allow rooms to be disinfected periodically, minimizing the risk of the onset and further transmission of diseases.

Similar devices are also used by tuberculosis patients. After all, such patients do not always receive treatment in a hospital. While at home, they need to disinfect their home, including using ultraviolet radiation.

Application in forensics

Scientists have developed a technology that allows detecting the minimum doses of explosives. For this, a device is used in which ultraviolet radiation is produced. Such a device is capable of detecting the presence of hazardous elements in the air and in water, on fabric, and also on the skin of a suspect in a crime.

Ultraviolet and infrared radiation also finds its application in macro photography of objects with invisible and barely visible traces of a committed offense. This allows forensic scientists to study documents and traces of a shot, texts that have undergone changes as a result of their flooding with blood, ink, etc.

Other uses of UV rays

Ultraviolet radiation is used:

In show business to create lighting effects and lighting;

In currency detectors;

In printing;

In animal husbandry and agriculture;

For catching insects;

In restoration;

For chromatographic analysis.

Ultraviolet radiation belongs to the invisible optical spectrum. The natural source of ultraviolet radiation is the sun, which accounts for approximately 5% of the solar radiation flux density - this is a vital factor that has a beneficial stimulating effect on a living organism.

Artificial sources of ultraviolet radiation (electric arc during electric welding, electric smelting, plasma torches, etc.) can cause damage to the skin and vision. Acute eye lesions (electrophthalmia) are acute conjunctivitis. The disease is manifested by the sensation of a foreign body or sand in the eyes, photophobia, lacrimation. Chronic diseases include chronic conjunctivitis, cataracts. Skin lesions occur in the form of acute dermatitis, sometimes with the formation of edema and blisters. There may be general toxic effects with fever, chills, headaches. Hyperpigmentation and peeling develop on the skin after intense irradiation. Prolonged exposure to ultraviolet radiation leads to "aging" of the skin, the likelihood of developing malignant neoplasms.

Hygienic regulation of ultraviolet radiation is carried out according to SN 4557-88, which establish the permissible radiation flux density depending on the wavelength, provided that the organs of vision and skin are protected.

Permissible exposure intensity of workers at
unprotected areas of the skin surface no more than 0.2 m 2 (face,
neck, hands) with a total duration of exposure to radiation of 50% of the work shift and the duration of a single exposure
over 5 minutes should not exceed 10 W / m 2 for the region of 400-280 nm and
0.01 W / m 2 - for the region of 315-280 nm.

When using special clothing and face protection
and hands that do not transmit radiation, the permissible intensity
exposure should not exceed 1 W/m 2 .

The main methods of protection against ultraviolet radiation include screens, personal protective equipment (clothing, glasses), protective creams.

Infrared radiation represents the invisible part of the optical electromagnetic spectrum, the energy of which, when absorbed in a biological tissue, causes a thermal effect. Sources of infrared radiation can be melting furnaces, molten metal, heated parts and blanks, various types of welding, etc.

The most affected organs are the skin and organs of vision. In case of acute skin irradiation, burns, a sharp expansion of capillaries, increased skin pigmentation are possible; with chronic exposure, changes in pigmentation can be persistent, for example, an erythema-like (red) complexion in glass workers, steel workers.

When exposed to vision, clouding and burns of the cornea, infrared cataracts can be noted.

Infrared radiation also affects metabolic processes in the myocardium, water and electrolyte balance, the state of the upper respiratory tract (the development of chronic laryngitis, rhinitis, sinusitis), and can cause heat stroke.

Rationing of infrared radiation is carried out according to the intensity of permissible integral radiation fluxes, taking into account the spectral composition, the size of the irradiated area, the protective properties of overalls for the duration of action in accordance with GOST 12.1.005-88 and Sanitary Rules and Norms SN 2.2.4.548-96 "Hygienic requirements for the microclimate of production premises."

The intensity of thermal exposure of workers from heated surfaces of technological equipment, lighting fixtures, insolation at permanent and non-permanent workplaces should not exceed 35 W / m 2 when irradiating 50% of the body surface or more, 70 W / m 2 - with the size of the irradiated surface from 25 to 50% and 100 W / m 2 - with irradiation of no more than 25% of the body surface.

The intensity of thermal exposure of workers from open sources (heated metal, glass, “open” flame, etc.) should not exceed 140 W / m 2, while more than 25% of the body surface should not be exposed to radiation and it is mandatory to use personal protective equipment, including including face and eye protection.

The permissible intensity of exposure to permanent and non-permanent places is given in Table. 4.20.

Table 4.20.

Permissible exposure intensity

The main measures to reduce the risk of exposure to infrared radiation on humans include: reducing the intensity of the radiation source; technical protective equipment; time protection, use of personal protective equipment, therapeutic and preventive measures.

Technical protective equipment is divided into enclosing, heat-reflecting, heat-removing and heat-insulating screens; equipment sealing; means of ventilation; means of automatic remote control and monitoring; alarm.

When protecting with time, in order to avoid excessive general overheating and local damage (burn), the duration of periods of continuous infrared irradiation of a person and pauses between them is regulated (Table 4.21. according to R 2.2.755-99).

Table 4.21.

Dependence of continuous irradiation on its intensity.

Questions to 4.4.3.

1. Describe the natural sources of the electromagnetic field.
2. Give a classification of anthropogenic electromagnetic fields.

3. Tell us about the effect of an electromagnetic field on a person.

4. What is the regulation of electromagnetic fields.

5. What are the permissible levels of exposure to electromagnetic fields in the workplace.

6. List the main measures to protect workers from the adverse effects of electromagnetic fields.

7. What screens are used to protect against electromagnetic fields.

8. What personal protective equipment is used and how their effectiveness is determined.

9. Describe the types of ionizing radiation.

10. What doses characterize the effect of ionizing radiation.

11. What is the effect of ionizing radiation on a person.

12. What is the regulation of ionizing radiation.

13. Tell us the procedure for ensuring safety when working with ionizing radiation.

14. Give the concept of laser radiation.

15. Describe its impact on humans and methods of protection.

16. Give the concept of ultraviolet radiation, its effects on humans and methods of protection.

17. Give the concept of infrared radiation, its effects on humans and methods of protection.

With the discovery of infrared radiation, the well-known German physicist Johann Wilhelm Ritter had a desire to study the opposite side of this phenomenon.

After some time, he managed to find out that at the other end it has considerable chemical activity.

This spectrum became known as ultraviolet rays. What it is and what effect it has on living terrestrial organisms, let's try to figure it out further.

Both radiations are in any case electromagnetic waves. Both infrared and ultraviolet, they limit the spectrum of light perceived by the human eye on both sides.

The main difference between these two phenomena is the wavelength. Ultraviolet has a fairly wide wavelength range - from 10 to 380 microns and is located between visible light and X-rays.

Differences between infrared and ultraviolet

IR radiation has the main property - to radiate heat, while ultraviolet has a chemical activity, which has a tangible effect on the human body.

How does ultraviolet radiation affect humans?

Due to the fact that UV is divided by the difference in wavelength, they biologically affect the human body in different ways, so scientists distinguish three sections of the ultraviolet range: UV-A, UV-B, UV-C: near, middle and far ultraviolet.

The atmosphere that envelops our planet acts as a protective shield that protects it from the Sun's ultraviolet flux. Far radiation is retained and absorbed almost completely by oxygen, water vapor, carbon dioxide. Thus, insignificant radiation enters the surface in the form of near and medium radiation.

The most dangerous is radiation with a short wavelength. If short-wave radiation falls on living tissues, it provokes an instant destructive effect. But due to the fact that our planet has an ozone shield, we are safe from the effects of such rays.

IMPORTANT! Despite natural protection, we use some inventions in everyday life that are sources of this particular range of rays. These are welding machines and ultraviolet lamps, which, unfortunately, cannot be abandoned.

Biologically, ultraviolet affects human skin as a slight redness, sunburn, which is a fairly mild reaction. But it is worth considering the individual feature of the skin, which can specifically respond to UV radiation.

Exposure to UV rays also adversely affects the eyes. Many are aware that ultraviolet affects the human body in one way or another, but not everyone knows the details, so let's try to understand this topic in more detail.

UV mutagenesis or how UV affects human skin

It is impossible to completely refuse the sun's rays on the skin, this leads to extremely unpleasant consequences.

But it is also contraindicated to go to extremes and try to acquire an attractive shade of the body, exhausting yourself under the merciless rays of the sun. What can happen in case of uncontrolled stay under the scorching sun?

If redness of the skin is found, this is not a sign that after a while, it will pass and a nice, chocolate tan will remain. The skin is darker due to the fact that the body produces a coloring pigment, melanin, which fights against the adverse effects of UV on our body.

Moreover, redness on the skin does not remain long, but it can lose elasticity forever. Epithelial cells may also begin to grow, visually reflected in the form of freckles and age spots, which will also remain for a long time, or even forever.

Penetrating deep into tissues, ultraviolet light can lead to ultraviolet mutagenesis, which is damage to cells at the gene level. The most dangerous can be melanoma, in case of metastasis of which death can occur.

How to protect yourself from ultraviolet radiation?

Is it possible to protect the skin from the negative effects of ultraviolet radiation? Yes, if, while on the beach, you follow just a few rules:

1. It is necessary to be under the scorching sun for a short time and at strictly defined hours, when the acquired light tan acts as photoprotection of the skin.
2. Be sure to use sunscreen. Before you buy this kind of product, be sure to check if it can protect you from UV-A and UV-B.
3. It is worth including in the diet foods that contain the maximum amount of vitamins C and E, as well as rich in antioxidants.

If you are not on the beach, but are forced to be in the open air, you should choose special clothes that can protect your skin from UV.

Electrophthalmia - the negative effect of UV radiation on the eyes

Electrophthalmia is a phenomenon that occurs as a result of the negative effects of ultraviolet radiation on the structure of the eye. UV waves from the middle ranges in this case are very damaging to human vision.

Electrophthalmia

These events most often occur when:

• A person observes the sun, its location, without protecting the eyes with special devices;
• Bright sun in open space (beach);
• The person is in a snowy area, in the mountains;
• Quartz lamps are placed in the room where the person is located.

Electrophthalmia can lead to corneal burns, the main symptoms of which are:

• Tearing of the eyes;
• Significant pain;
• Fear of bright light;
• Redness of the protein;
• Edema of the epithelium of the cornea and eyelids.

About statistics, the deep layers of the cornea do not have time to be damaged, therefore, when the epithelium heals, vision is fully restored.

How to provide first aid for electrophthalmia?

If a person is faced with the above symptoms, it is not only aesthetically unpleasant, but can also cause unimaginable suffering.

First aid is pretty simple:

• First rinse eyes with clean water;
• Then apply moisturizing drops;
• Put on glasses;

To get rid of pain in the eyes, it is enough to make a compress from wet black tea bags, or grate raw potatoes. If these methods do not help, you should immediately seek help from a specialist.

To avoid such situations, it is enough to purchase social sunglasses. The UV-400 marking indicates that this accessory is able to protect the eyes from all UV radiation.

How is UV radiation used in medical practice?

In medicine, there is the concept of "ultraviolet starvation", which can occur in case of prolonged avoidance of sunlight. In this case, unpleasant pathologies may arise, which can be easily avoided using artificial sources of ultraviolet radiation.

Their small impact is able to compensate for the lack of winter vitamin D deficiency.

In addition, such therapy is applicable in case of joint problems, skin diseases and allergic reactions.

With UV radiation, you can:

• Increase hemoglobin, but lower sugar levels;
• Normalize the work of the thyroid gland;
• Improve and eliminate problems of the respiratory and endocrine system;
• With the help of installations with ultraviolet radiation, rooms and surgical instruments are disinfected;
• UV rays have bactericidal properties, which is especially useful for patients with purulent wounds.

IMPORTANT! Always, using such radiation in practice, it is worth familiarizing yourself not only with the positive, but also with the negative aspects of their impact. It is strictly forbidden to use artificial, as well as natural UV radiation as a treatment for oncology, bleeding, stage 1 and 2 hypertension, and active tuberculosis.

I remember disinfection with UV lamps from childhood - in the kindergarten, sanatorium and even in the summer camp there were somewhat frightening structures that glowed with a beautiful purple light in the dark and from which the educators drove us away. So what exactly is ultraviolet radiation and why does a person need it?

Perhaps the first question to be answered is what ultraviolet rays are and how they work. This is usually referred to as electromagnetic radiation, which is in the range between visible and X-ray radiation. Ultraviolet is characterized by a wavelength from 10 to 400 nanometers.
It was discovered back in the 19th century, and this happened thanks to the discovery of infrared radiation. Having discovered the IR spectrum, in 1801 I.V. Ritter drew attention to the opposite end of the light spectrum during experiments with silver chloride. And then several scientists at once came to the conclusion about the heterogeneity of the ultraviolet.

Today it is divided into three groups:

• UV-A radiation - near ultraviolet;
• UV-B - medium;
• UV-C - far.

This division is largely due to the impact of rays on a person. The natural and main source of ultraviolet radiation on Earth is the Sun. In fact, it is from this radiation that we are saved by sunscreens. At the same time, far ultraviolet is completely absorbed by the Earth's atmosphere, and UV-A just reaches the surface, causing a pleasant tan. And on average, 10% of UV-B provokes those same sunburns, and can also lead to the formation of mutations and skin diseases.

Artificial sources of ultraviolet are created and used in medicine, agriculture, cosmetology and various sanitary institutions. Generation of ultraviolet radiation is possible in several ways: by temperature (incandescent lamps), by the movement of gases (gas lamps) or metal vapors (mercury lamps). At the same time, the power of such sources varies from a few watts, usually small mobile radiators, to a kilowatt. The latter are mounted in volumetric stationary installations. The areas of application of UV rays are due to their properties: the ability to accelerate chemical and biological processes, the bactericidal effect and the luminescence of certain substances.

Ultraviolet is widely used to solve a variety of problems. In cosmetology, the use of artificial UV radiation is used primarily for tanning. Solariums produce rather mild UV-A according to the introduced standards, and the share of UV-B in tanning lamps is no more than 5%. Modern psychologists recommend solariums for the treatment of "winter depression", which is mainly caused by vitamin D deficiency, as it is formed under the influence of UV rays. Also, UV lamps are used in manicure, since it is in this spectrum that especially resistant gel polishes, shellac and the like dry out.

Ultraviolet lamps are used to create photographs in non-standard situations, for example, to capture space objects that are invisible to a conventional telescope.

Ultraviolet is widely used in expert activities. With its help, the authenticity of the paintings is checked, since fresher paints and varnishes in such rays look darker, which means that the real age of the work can be established. Forensics also use UV rays to detect traces of blood on objects. In addition, ultraviolet light is widely used to develop hidden seals, security features and document authentication threads, as well as in the lighting design of shows, restaurant signs or decorations.

In healthcare facilities, ultraviolet lamps are used to sterilize surgical instruments. In addition, air disinfection using UV rays is still widespread. There are several types of such equipment.

So called high and low pressure mercury lamps, as well as xenon flash lamps. The bulb of such a lamp is made of quartz glass. The main advantage of germicidal lamps is their long service life and instantaneous ability to work. Approximately 60% of their rays are in the bactericidal spectrum. Mercury lamps are quite dangerous in operation; in case of accidental damage to the housing, thorough cleaning and demercurization of the room is necessary. Xenon lamps are less dangerous if damaged and have a higher bactericidal activity. Also bactericidal lamps are divided into ozone and ozone-free. The former are characterized by the presence in their spectrum of a wave with a length of 185 nanometers, which interacts with oxygen in the air and turns it into ozone. High concentrations of ozone are dangerous for humans, and the use of such lamps is strictly limited in time and is recommended only in a ventilated area. All this led to the creation of ozone-free lamps, the bulb of which is coated with a special coating that does not transmit a wave of 185 nm to the outside.

Regardless of the type, bactericidal lamps have common drawbacks: they work in complex and expensive equipment, the average life of the emitter is 1.5 years, and the lamps themselves, after burnout, must be stored packed in a separate room and disposed of in a special way in accordance with current regulations.

Consist of a lamp, reflectors and other auxiliary elements. Such devices are of two types - open and closed, depending on whether UV rays pass out or not. Open emit ultraviolet, enhanced by reflectors, into the space around, capturing almost the entire room at once, if installed on the ceiling or wall. It is strictly forbidden to treat the premises with such an irradiator in the presence of people.
Closed irradiators work on the principle of a recirculator, inside which a lamp is installed, and the fan draws air into the device and releases the already irradiated air to the outside. They are placed on the walls at a height of at least 2 m from the floor. They can be used in the presence of people, but long-term exposure is not recommended by the manufacturer, as part of the UV rays can pass out.
Among the shortcomings of such devices, one can note immunity to mold spores, as well as all the difficulties of recycling lamps and strict regulations for use, depending on the type of emitter.

Germicidal installations

A group of irradiators combined into one device used in one room is called a bactericidal installation. Usually they are quite large and are characterized by high power consumption. Air treatment with bactericidal installations is carried out strictly in the absence of people in the room and is monitored according to the Commissioning Certificate and the Registration and Control Log. It is used only in medical and hygienic institutions for disinfection of both air and water.

Disadvantages of ultraviolet air disinfection

In addition to those already listed, the use of UV emitters has other disadvantages. First of all, ultraviolet itself is dangerous for the human body, it can not only cause skin burns, but also affect the functioning of the cardiovascular system, it is dangerous for the retina. In addition, it can cause the appearance of ozone, and with it the unpleasant symptoms inherent in this gas: irritation of the respiratory tract, stimulation of atherosclerosis, exacerbation of allergies.

The effectiveness of UV lamps is quite controversial: the inactivation of pathogens in the air by permitted doses of ultraviolet radiation occurs only when these pests are static. If microorganisms move, interact with dust and air, then the required radiation dose increases by 4 times, which a conventional UV lamp cannot create. Therefore, the efficiency of the irradiator is calculated separately, taking into account all the parameters, and it is extremely difficult to choose the right ones for influencing all types of microorganisms at once.

Penetration of UV rays is relatively shallow, and even if the immobile viruses are under a layer of dust, the upper layers protect the lower ones by reflecting ultraviolet from themselves. So, after cleaning, disinfection must be carried out again.
UV irradiators cannot filter the air, they only fight microorganisms, keeping all mechanical pollutants and allergens in their original form.