The life of people, plants and animals is in close connection with the Sun. It emits radiation that has special properties. Ultraviolet is considered indispensable and vital. With its deficiency, extremely undesirable processes in the body begin, and a strictly dosed amount can cure serious illnesses.
Therefore, an ultraviolet lamp for home use is necessary for many. Let's talk about how to choose it correctly.
Ultraviolet radiation is invisible to humans, occupying the region between the X-ray and visible spectrum. The wavelengths of its constituent waves range from 10 to 400 nanometers. Physicists conditionally divide the ultraviolet spectrum into near and far, and also distinguish three types of its constituent rays. Radiation C is classified as hard, with a relatively long exposure, it is capable of killing living cells.
In nature, it practically does not occur, except perhaps high in the mountains. But it can be obtained in artificial conditions. Radiation B is considered medium in hardness. That is what affects people in the middle of a hot summer day. May cause harm if used inappropriately. And, finally, the softest and most useful are rays of type A. They can even cure a person from certain diseases.
Ultraviolet light has a wide range of applications in medicine and other fields. First of all, because in its presence, vitamin D is produced in the body, which is necessary for the normal development of the child and the health of adults. This element makes bones stronger, strengthens the immune system and enables the body to properly absorb a number of essential trace elements.
In addition, doctors have proven that under the influence of ultraviolet radiation, serotonin, the hormone of happiness, is synthesized in the brain. That is why we love sunny days so much and fall into a kind of depression when the sky is overcast. In addition, ultraviolet light is used in medicine as a bactericidal, antimyotic and mutagenic agent. The therapeutic effect of radiation is also known.
The radiation of the ultraviolet spectrum is inhomogeneous. Physicists distinguish three groups of its constituent rays. The most dangerous for the living rays of group C, the hardest radiation
Strictly dosed rays directed at a certain area give a good therapeutic effect in a number of diseases. A new industry has emerged - laser biomedicine, which uses ultraviolet light. It is used to diagnose ailments and to monitor the condition of organs after operations.
UV radiation has also found wide application in cosmetology, where it is most often used to get a tan and fight some skin problems.
Do not underestimate the deficiency of ultraviolet light. When it appears, a person suffers from beriberi, immunity decreases and malfunctions in the functioning of the nervous system are diagnosed. A tendency to depression and mental instability is formed. Considering all these factors, for those who wish, household versions of ultraviolet lamps for various purposes have been developed and produced. Let's get to know them better.
Irradiation with hard ultraviolet for the purpose of disinfection of premises has been successfully used in medicine for decades. Similar activities can be carried out at home.
UV lamps: what are they
Special ultraviolet lamps are produced, designed for the normal growth of plants suffering from a lack of sunlight.
At the same time, it must be understood that destruction occurs only in the reach of the rays, which, unfortunately, are not able to penetrate very deep into the wall or upholstery of upholstered furniture. To combat microorganisms, exposure of various durations is required. It is worst tolerated by sticks and cocci. The simplest microorganisms, spore bacteria and fungi are most resistant to ultraviolet radiation.
However, if you choose the right exposure time, you can completely disinfect the room. This will take an average of 20 minutes. During this time, you can get rid of pathogens, mold and fungal spores, etc.
For quick and efficient drying of various types of manicure gel polish, special ultraviolet lamps are used.
The principle of operation of a standard UV lamp is extremely simple. It is a flask filled with gaseous mercury. Electrodes are fixed at its ends.
When voltage is applied between them, an electric arc is formed, which evaporates mercury, which becomes a source of powerful light energy. Depending on the design of the device, its main characteristics differ.
Quartz emitting devices
The flask for these lamps is made of quartz, which has a direct impact on the quality of their radiation. They emit rays in the "hard" UV range of 205-315 nm. For this reason, quartz devices have an effective disinfecting effect. They cope very well with all known bacteria, viruses, other microorganisms, unicellular algae, spores of various types of mold and fungi.
Open-type UV lamps can be compact. Such devices are very good at disinfecting clothes, shoes and other items.
You need to know that UV waves with a length of less than 257 nm activate the formation of ozone, which is considered the strongest oxidizing agent. Due to this, in the process of disinfection, ultraviolet acts together with ozone, which makes it possible to destroy microorganisms quickly and efficiently.
However, such lamps have a significant disadvantage. Their impact is dangerous not only for pathogenic microflora, but also for all living cells. This means that animals, people and plants must be removed from the lamp area during the disinfection process. Given the name of the device, the disinfection procedure is called quartz treatment.
It is used to disinfect hospital wards, operating rooms, catering establishments, industrial premises, etc. The simultaneous use of ozonation makes it possible to prevent the development of pathogenic microflora and rotting, to keep the freshness of products longer in warehouses or in stores. Such lamps can be used for therapeutic purposes.
Germicidal ultraviolet emitters
The main difference from the device described above is the material of the flask. In germicidal lamps, it is made of uviol glass. This material well delays the waves of the "hard" range, so that ozone is not formed during the operation of the equipment. Thus, disinfection is carried out only by exposure to safer soft radiation.
Uviolet glass, from which the bulb of bactericidal lamps is made, completely delays hard radiation. For this reason, the device is less effective.
Such devices do not pose a great threat to humans and animals, but the time and exposure to pathogenic microflora should be significantly increased. Such devices are recommended for use at home. In medical institutions and institutions equivalent to them, they can function continuously. In this case, it is necessary to close the lamps with a special casing that will direct the glow upwards.
This is necessary to protect the eyesight of visitors and workers. Germicidal lamps are absolutely safe for the respiratory system, since they do not emit ozone, but are potentially harmful to the cornea of the eye. Prolonged exposure to it can lead to burns, which over time will cause visual impairment. For this reason, it is advisable to use special goggles that protect the eyes while the device is in operation.
Amalgam devices
Improved and therefore safer to use UV lamps. Their peculiarity lies in the fact that mercury inside the flask is present not in a liquid, but in a bound state. It is part of the hard amalgam that covers the inside of the lamp.
Amalgam is an alloy of indium and bismuth with the addition of mercury. In the process of heating, the latter begins to evaporate and emit ultraviolet radiation.
Inside the amalgam-type ultraviolet lamps is an alloy containing mercury. Due to the fact that the substance is bound, the device is completely safe even after the flask is damaged.
During the operation of amalgam-type devices, the release of ozone is excluded, which makes them safe. The bactericidal effect is very high. The design features of such lamps make them safe even in case of careless handling. If the cold flask is broken for any reason, it can simply be thrown into the nearest trash can. In case of damage to the integrity of a burning lamp, everything is a little more complicated.
Mercury vapor will come out of it, because they are hot amalgam. However, their number is minimal and they will not cause harm. In comparison, if a bactericidal or quartz device breaks, there is a real threat to health.
Each contains about 3 g of liquid mercury, which can be hazardous if spilled. For this reason, such lamps must be disposed of in a special way, and the place where mercury is spilled is treated by specialists.
Another advantage of amalgam devices is their durability. Compared to analogues, their service life is at least twice as high. This is due to the fact that flasks coated with amalgam from the inside do not lose their transparency. Whereas lamps with liquid mercury are gradually covered with a dense, slightly transparent coating, which significantly reduces their service life.
How not to make a mistake in choosing a device
Before making a decision to buy a device, you should determine exactly whether it is really so necessary. The purchase will be completely justified if there are some indications. The lamp can be used to disinfect rooms, water, common areas, etc.
You need to understand that you should not get too carried away with this, since life in sterile conditions has a very adverse effect on immunity, especially for children.
Before buying an ultraviolet lamp, you need to decide for what purpose it will be used. You need to understand that you need to use it very carefully and only after consulting a doctor.
Therefore, doctors recommend using the device wisely in families with frequently ill children during seasonal illnesses. The device will be useful in the process of caring for bedridden patients, as it allows not only to disinfect the room, but also helps to fight pressure sores, eliminates unpleasant odors, etc. A UV lamp can cure some diseases, but in this case it is used only on the recommendation of a doctor.
Ultraviolet helps with inflammation of the upper respiratory tract, dermatitis of various origins, psoriasis, neuritis, rickets, flu and colds, in the treatment of ulcers and difficult-to-heal wounds, and gynecological problems. It is possible to use UV emitters at home for cosmetic purposes. In this way, you can get a beautiful tan and get rid of skin problems, dry your nails covered with a special varnish.
In addition, special lamps for water disinfection and devices that stimulate the growth of domestic plants are produced. All of them have specific features that do not allow them to be used for other purposes. Thus, the range of household UV lamps is very large. There are quite a few universal options among them, so before buying you need to know exactly for what purposes and how often the device will be used.
A closed type UV lamp is the safest option for those indoors. The scheme of its action is shown in the figure. The air is disinfected inside the protective housing
In addition, there are a number of factors that must be taken into account when choosing.
Household uv lamp type
For work at home, manufacturers produce three types of equipment:
- open lamps. Ultraviolet from the source propagates unhindered. The use of such devices is limited by the characteristics of the lamp. Most often they are turned on for a strictly defined time, animals and people are removed from the premises.
- Closed devices or recirculators. Air is supplied inside the protected housing of the device, where it is disinfected, after which it enters the room. Such lamps are not dangerous to others, so they can work in the presence of people.
- Specialized equipment designed to perform specific tasks. Most often it is completed with a set of nozzles-tubes.
Device mounting method
The manufacturer offers to choose a suitable model from two main options: stationary and mobile. In the first case, the device is fixed at the place chosen for this. There are no plans to move. Such devices can be fixed to the ceiling or to the wall. The latter option is more popular. A distinctive feature of stationary devices is their high power, which allows them to process a room of a large area.
More powerful, as a rule, devices with a stationary mount. They are mounted on the wall or on the ceiling so that during operation they cover the entire area of the room.
Most often, closed recirculator lamps are produced in this design. Mobile devices are less powerful, but they can be easily moved to another location. It can be both closed and open lamps. The latter are especially suitable for disinfecting small spaces: wardrobes, bathrooms and toilets, etc. Mobile devices are usually installed on the floor or on tables, which is quite convenient.
Moreover, floor models have great power and are quite capable of processing a room of impressive size. Most of the specialized equipment is mobile. Relatively recently, interesting models of UV emitters have appeared. These are peculiar hybrids of a lamp and a bactericidal lamp with two or two operating modes. They work as lighting devices or disinfect the room.
UV emitter power
For the correct use of a UV lamp, it is important that its power matches the size of the room in which it will be used. The manufacturer usually indicates the so-called "room coverage" in the technical data sheet of the product. This is the area that is affected by the device. If there is no such information, the power of the device will be indicated.
The coverage area of the equipment and the time of its exposure depend on the power. When choosing a UV lamp, this must be taken into account
On average, for rooms up to 65 cubic meters. m will be enough device with a power of 15 watts. This means that such a lamp can be safely purchased if the area of the processed rooms is from 15 to 35 square meters. m with a height of not more than 3 m. More powerful specimens that produce 36 W must be purchased for rooms with an area of 100-125 cubic meters. m with a standard ceiling height.
The most popular models of UV lamps
The range of ultraviolet emitters intended for home use is quite wide. Domestic manufacturers produce high-quality, efficient and quite affordable equipment. Let's take a look at some of these devices.
Various modifications of the Sun apparatus
Under this brand, open-type quartz emitters of various capacities are produced. Most models are designed for disinfection of surfaces and space, the area of which is not more than 15 square meters. m. In addition, the device can be used for therapeutic irradiation of adults and children older than three years of age. The device is multifunctional, therefore it is considered universal.
The ultraviolet emitter Sun is especially popular. This universal device is capable of disinfecting the space and performing therapeutic procedures, for which it is completed with a set of special nozzles
The case is equipped with a special protective screen, which is used during medical procedures and is removed when disinfecting the room. Depending on the model, the equipment is equipped with a set of special nozzles or tubes for various therapeutic procedures.
Compact emitters Crystal
Another sample of domestic production. It is a small mobile device. Designed exclusively for the disinfection of space, the volume of which does not exceed 60 cubic meters. m. These parameters correspond to a room of standard height with an area of \u200b\u200bno more than 20 square meters. m. The device is an open type lamp, therefore, requires proper handling.
Compact mobile UV emitter Crystal is very convenient to use. It is important not to forget to remove plants, animals and people from its zone of action.
During the operation of the equipment, plants, animals and people must be removed from the area of its operation. Structurally, the device is very simple. There is no timer and automatic shutdown system. For this reason, the user must independently monitor the operating time of the device. If necessary, the UV lamp can be replaced with a standard fluorescent one, and then the equipment will work like a normal lamp.
Bactericidal recirculators RZT and ORBB series
These are powerful closed-type devices. Designed for disinfection and air purification. The devices are equipped with a UV lamp, which is located inside a closed protective housing. Air is sucked into the device under the action of a fan, after processing it is supplied outside. Thanks to this, the device can function in the presence of people, plants or animals. They don't get negative impact.
Depending on the model, the devices can be additionally equipped with filters that trap particles of dirt and dust. The equipment is mainly produced in the form of stationary devices with a wall mount, there are also ceiling options. In some cases, the device can be removed from the wall and placed on a table.
Conclusions and useful video on the topic
Getting to know Sunshine UV lamps:
How the crystal germicidal lamp works:
Choosing the right UV emitter for your home:
Ultraviolet is necessary for every living being. Unfortunately, it is not always possible to get enough of it. In addition, UV rays are a powerful weapon against a wide variety of microorganisms and pathogenic microflora. Therefore, many are thinking about buying a household ultraviolet emitter. When making a choice, do not forget that you need to use the device very carefully. It is necessary to strictly follow the recommendations of doctors and not overdo it. Large doses of ultraviolet radiation are very dangerous for all living things.
We most often observe the use of ultraviolet radiation for cosmetic and medical purposes. Also, ultraviolet radiation is used in printing, in the disinfection and disinfection of water and air, if necessary, polymerization and changes in the physical state of materials.
Ultraviolet radiation is a type of radiation that has a certain wavelength and occupies an intermediate position between the X-ray and the violet zone of visible radiation. This radiation is invisible to the human eye. However, due to its properties, such radiation has become very widespread and is used in many areas.
Currently, many scientists are purposefully studying the effect of ultraviolet radiation on many life processes, including metabolic, regulatory, and trophic ones. It is known that ultraviolet radiation has a beneficial effect on the body in certain diseases and disorders, contributing to the treatment. That is why it has been widely used in the field of medicine.
Thanks to the work of many scientists, the effect of ultraviolet radiation on biological processes in the human body has been studied so that these processes can be controlled.
UV protection is essential when the skin is exposed to the sun for a long time.
It is believed that it is ultraviolet rays that are responsible for photoaging of the skin, as well as for the development of carcinogenesis, since when exposed to them, a lot of free radicals that adversely affect all processes in the body.
In addition, when using ultraviolet radiation, the risk of damaging DNA chains is very high, and this can already lead to very tragic consequences and the emergence of such terrible diseases as cancer and others.
Do you know what can be useful for a person? About such properties, as well as about the properties of ultraviolet radiation, which allow it to be used in various production processes, you can learn everything from our article.
We also have an overview available. Read our material and you will understand all the main differences between natural and artificial light sources.
The main natural source of this type of radiation is the sun. And among the artificial ones, there are several types:
- Erythema lamps (invented in the 60s, used mainly to compensate for the lack of natural ultraviolet radiation. For example, to prevent rickets in children, to irradiate the young generation of farm animals, in fotaria)
- Mercury-quartz lamps
- Excilamps
- germicidal lamps
- Fluorescent lamps
- LEDs
Many lamps emitting in the ultraviolet range are designed to illuminate rooms and other objects, and the principle of their operation is associated with ultraviolet radiation, which is converted in various ways into visible light.
Ways to generate ultraviolet radiation:
- Temperature radiation (used in incandescent lamps)
- Radiation created due to gases and metal vapors moving in an electric field (used in mercury and gas discharge lamps)
- Luminescence (used in erythema, bactericidal lamps)
The use of ultraviolet radiation due to its properties
The industry produces many types of lamps for various applications of ultraviolet radiation:
- Mercury
- Hydrogen
- Xenon
The main properties of UV - radiation, which determine its use:
- High chemical activity (contributes to the acceleration of many chemical reactions, as well as the acceleration of biological processes in the body):
Under the influence of ultraviolet radiation, vitamin D and serotonin are formed in the skin, the tone and vital activity of the body improves. - Ability to kill various microorganisms (bactericidal property):
The use of ultraviolet germicidal radiation contributes to air disinfection, especially in places where many people gather (hospitals, schools, universities, railway stations, subways, large stores).
Disinfection of water with ultraviolet radiation is also in great demand, as it gives good results. With this method of purification, water does not acquire an unpleasant odor and taste. It is great for water purification in fish farms, swimming pools.
The ultraviolet disinfection method is often used during processing surgical instruments. - The ability to cause luminescence of certain substances:
Thanks to this property, forensic experts detect traces of blood on various objects. And also thanks to special paint you can detect marked banknotes that are used in anti-corruption operations.
Application of ultraviolet radiation photo
Below are photos on the topic of the article "The use of ultraviolet radiation." To open the photo gallery, just click on the image thumbnail.
and violet), ultraviolet rays, UV radiation, electromagnetic radiation not visible to the eye, occupying the spectral region between visible and X-ray radiation within the wavelengths λ 400-10 nm. The entire region of ultraviolet radiation is conditionally divided into near (400-200 nm) and far, or vacuum (200-10 nm); the last name is due to the fact that the ultraviolet radiation of this area is strongly absorbed by air and its study is carried out using vacuum spectral instruments.
Near ultraviolet radiation was discovered in 1801 by the German scientist N. Ritter and the English scientist W. Wollaston on the photochemical effect of this radiation on silver chloride. Vacuum ultraviolet radiation was discovered by the German scientist W. Schumann using a vacuum spectrograph with a fluorite prism built by him (1885-1903) and gelatin-free photographic plates. He was able to register short-wave radiation up to 130 nm. The English scientist T. Lyman, who first built a vacuum spectrograph with a concave diffraction grating, recorded ultraviolet radiation with a wavelength of up to 25 nm (1924). By 1927, the entire gap between vacuum ultraviolet radiation and X-ray radiation had been studied.
The spectrum of ultraviolet radiation can be linear, continuous, or consist of bands, depending on the nature of the source of ultraviolet radiation (see Optical Spectra). The UV radiation of atoms, ions or light molecules (for example, H 2) has a line spectrum. The spectra of heavy molecules are characterized by bands due to electronic-vibrational-rotational transitions of molecules (see Molecular Spectra). A continuous spectrum arises during deceleration and recombination of electrons (see Bremsstrahlung).
Optical properties of substances.
The optical properties of substances in the ultraviolet region of the spectrum differ significantly from their optical properties in the visible region. A characteristic feature is the decrease in transparency (increase in the absorption coefficient) of most bodies that are transparent in the visible region. For example, ordinary glass is opaque at λ< 320 нм; в более коротковолновой области прозрачны лишь увиолевое стекло, сапфир, фтористый магний, кварц, флюорит, фтористый литий и некоторые другие материалы. Наиболее далёкую границу прозрачности (105 нм) имеет фтористый литий. Для λ < 105 нм прозрачных материалов практически нет. Из газообразных веществ наибольшую прозрачность имеют инертные газы, граница прозрачности которых определяется величиной их ионизационного потенциала. Самую коротковолновую границу прозрачности имеет гелий - 50,4 нм. Воздух непрозрачен практически при λ < 185 нм из-за поглощения кислородом.
The reflectance of all materials (including metals) decreases with decreasing wavelength of radiation. For example, the reflectance of freshly deposited aluminum, one of the best materials for reflective coatings in the visible region of the spectrum, decreases sharply at λ< 90 нм (Fig. 1). The reflection of aluminum is also significantly reduced due to surface oxidation. Lithium fluoride or magnesium fluoride coatings are used to protect the aluminum surface from oxidation. In the region λ< 80 нм некоторые материалы имеют коэффициент отражения 10-30% (золото, платина, радий, вольфрам и др.), однако при λ < 40 нм и их коэффициент отражения снижается до 1% и меньше.
Sources of ultraviolet radiation.
The radiation of solids heated up to 3000 K contains a significant fraction of continuous spectrum ultraviolet radiation, the intensity of which increases with increasing temperature. More powerful ultraviolet radiation is emitted by gas discharge plasma. In this case, depending on the discharge conditions and the working substance, both a continuous and a line spectrum can be emitted. For various applications of ultraviolet radiation, industry produces mercury, hydrogen, xenon and other gas-discharge lamps, the windows of which (or the entire flasks) are made of materials transparent to ultraviolet radiation (most often quartz). Any high-temperature plasma (plasma of electric sparks and arcs, plasma formed by focusing powerful laser radiation in gases or on the surface of solids, and so on) is a powerful source of ultraviolet radiation. Intense continuous spectrum ultraviolet radiation is emitted by electrons accelerated in a synchrotron (synchrotron radiation). Optical quantum generators (lasers) have also been developed for the ultraviolet region of the spectrum. The shortest wavelength has a hydrogen laser (109.8 nm).
Natural sources of ultraviolet radiation - the Sun, stars, nebulae and other space objects. However, only the long-wavelength part of ultraviolet radiation (λ > 290 nm) reaches the earth's surface. Shorter wavelength ultraviolet radiation is absorbed by ozone, oxygen and other components of the atmosphere at a height of 30-200 km from the Earth's surface, which plays an important role in atmospheric processes. The ultraviolet radiation of stars and other cosmic bodies, in addition to absorption in the earth's atmosphere, in the range of 91.2-20 nm is almost completely absorbed by interstellar hydrogen.
UV receivers.
Conventional photographic materials are used to register ultraviolet radiation at λ > 230 nm. In the shorter wavelength region, special low-gelatin photolayers are sensitive to it. Photoelectric receivers are used that use the ability of ultraviolet radiation to cause ionization and the photoelectric effect: photodiodes, ionization chambers, photon counters, photomultipliers, etc. A special type of photomultipliers has also been developed - channel electron multipliers, which allow creating microchannel plates. In such plates, each cell is a channel electron multiplier up to 10 µm in size. Microchannel plates make it possible to obtain photoelectric images in ultraviolet radiation and combine the advantages of photographic and photoelectric methods of radiation registration. In the study of ultraviolet radiation, various luminescent substances are also used that convert ultraviolet radiation into visible radiation. On this basis, devices for visualizing images in ultraviolet radiation have been created.
The use of ultraviolet radiation.
The study of emission, absorption and reflection spectra in the UV region makes it possible to determine the electronic structure of atoms, ions, molecules, and solids. The UV spectra of the Sun, stars, and others carry information about the physical processes occurring in the hot regions of these cosmic objects (see Ultraviolet spectroscopy, Vacuum spectroscopy). Photoelectron spectroscopy is based on the photoelectric effect caused by ultraviolet radiation. Ultraviolet radiation can break chemical bonds in molecules, as a result of which various chemical reactions can occur (oxidation, reduction, decomposition, polymerization, and so on, see Photochemistry). Luminescence under the action of ultraviolet radiation is used in the creation of fluorescent lamps, luminous paints, in luminescent analysis and luminescent flaw detection. Ultraviolet radiation is used in forensics to establish the identity of dyes, the authenticity of documents, and the like. In art criticism, ultraviolet radiation makes it possible to detect traces of restorations that are not visible to the eye in paintings. (Fig. 2). The ability of many substances to selectively absorb ultraviolet radiation is used to detect harmful impurities in the atmosphere, as well as in ultraviolet microscopy.
Meyer A., Seitz E., Ultraviolet radiation, trans. from German., M., 1952; Lazarev D.N., Ultraviolet radiation and its application, L. - M., 1950; Samson I. A. R., Techniques of vacuum ultraviolet spectroscopy, N. Y. - L. - Sydney, ; Zaidel A. N., Shreider E. Ya., Spectroscopy of vacuum ultraviolet, M., 1967; Stolyarov K. P., Chemical analysis in ultraviolet rays, M. - L., 1965; Baker A., Betteridzh D., Photoelectron spectroscopy, trans. from English, M., 1975.
Rice. Fig. 1. Dependences of the reflection coefficient r of the aluminum layer on the wavelength.
Rice. 2. Action spectra of ultra. izl. for biological objects.
Rice. 3. Survival of bacteria depending on the dose of ultraviolet radiation.
Biological action of ultraviolet radiation.
When exposed to living organisms, ultraviolet radiation is absorbed by the upper layers of plant tissues or the skin of humans and animals. The biological action of ultraviolet radiation is based on chemical changes in the molecules of biopolymers. These changes are caused both by the direct absorption of radiation quanta by them and (to a lesser extent) by the radicals of water and other low molecular weight compounds formed during irradiation.
Small doses of ultraviolet radiation have a beneficial effect on humans and animals - they contribute to the formation of vitamins of the group D(see Calciferols), improve the immunobiological properties of the body. A characteristic reaction of the skin to ultraviolet radiation is a specific redness - erythema (ultraviolet radiation with λ = 296.7 nm and λ = 253.7 nm has the maximum erythemal effect), which usually turns into protective pigmentation (tanning). Large doses of ultraviolet radiation can cause eye damage (photophthalmia) and skin burns. Frequent and excessive doses of ultraviolet radiation can in some cases be carcinogenic to the skin.
In plants, ultraviolet radiation changes the activity of enzymes and hormones, affects the synthesis of pigments, the intensity of photosynthesis and the photoperiodic reaction. It has not been established whether small doses of ultraviolet radiation are useful and even more necessary for the germination of seeds, the development of seedlings, and the normal functioning of higher plants. Large doses of ultraviolet radiation are undoubtedly unfavorable for plants, as evidenced by their protective adaptations (for example, the accumulation of certain pigments, cellular mechanisms of recovery from damage).
Ultraviolet radiation has a detrimental and mutagenic effect on microorganisms and cultivated cells of higher animals and plants (ultraviolet radiation with λ in the range of 280-240 nm is most effective). Usually, the spectrum of lethal and mutagenic action of ultraviolet radiation approximately coincides with the absorption spectrum of nucleic acids - DNA and RNA (Fig. 3, A), in some cases the spectrum of biological action is close to the absorption spectrum of proteins (Fig. 3, B). The main role in the action of ultraviolet radiation on cells belongs, apparently, to chemical changes in DNA: the pyrimidine bases (mainly thymine) included in its composition, when absorbing ultraviolet radiation quanta, form dimers that prevent normal doubling (replication) of DNA when preparing the cell for division . This can lead to cell death or changes in their hereditary properties (mutations). Damage to bioforest membranes and disruption of the synthesis of various components of membranes and cell membranes also play a certain role in the lethal effect of ultraviolet radiation on cells.
Most living cells can recover from damage caused by ultraviolet radiation due to the presence of their repair systems. The ability to recover from damage caused by ultraviolet radiation probably arose early in evolution and played an important role in the survival of primary organisms exposed to intense solar ultraviolet radiation.
According to the sensitivity to ultraviolet radiation, biological objects differ very much. For example, the dose of ultraviolet radiation that causes the death of 90% of cells for different strains of Escherichia coli is 10, 100 and 800 erg / mm 2, and for bacteria Micrococcus radiodurans - 7000 erg / mm 2 (Fig. 4, A and B). The sensitivity of cells to ultraviolet radiation to a large extent also depends on their physiological state and cultivation conditions before and after irradiation (temperature, composition of the nutrient medium, etc.). Mutations of certain genes strongly affect the sensitivity of cells to ultraviolet radiation. About 20 genes are known in bacteria and yeast, mutations in which increase sensitivity to ultraviolet radiation. In some cases, these genes are responsible for the recovery of cells from radiation damage. Mutations of other genes disrupt protein synthesis and the structure of cell membranes, thereby increasing the radiosensitivity of non-genetic components of the cell. Mutations that increase sensitivity to ultraviolet radiation are also known in higher organisms, including humans. Thus, a hereditary disease - xeroderma pigmentosum is caused by mutations in the genes that control dark repair.
The genetic consequences of exposure to ultraviolet radiation of pollen of higher plants, plant and animal cells, as well as microorganisms are expressed in an increase in the frequency of mutation of genes, chromosomes and plasmids. The frequency of mutation of individual genes, under the influence of high doses of ultraviolet radiation, can increase thousands of times compared to the natural level and reaches several percent. In contrast to the genetic action of ionizing radiation, gene mutations under the influence of ultraviolet radiation occur relatively more often than chromosome mutations. Due to the strong mutagenic effect, ultraviolet radiation is widely used both in genetic research and in the selection of plants and industrial microorganisms that are producers of antibiotics, amino acids, vitamins, and protein biomass. The genetic action of ultraviolet radiation could play a significant role in the evolution of living organisms. On the use of ultraviolet radiation in medicine, see Light therapy.
Samoilova K. A., The effect of ultraviolet radiation on the cell, L., 1967; Dubrov A.P., Genetic and physiological effects of ultraviolet radiation on higher plants, M., 1968; Galanin N. F., Radiant energy and its hygienic significance, L., 1969; Smith K., Hanewalt F., Molecular photobiology, trans. from English, M., 1972; Shulgin I. A., Plant and sun, L., 1973; Myasnik M.N., Genetic control of radiosensitivity of bacteria, M., 1974.
In agricultural production, for the technological impact of optical radiation on living organisms and plants, special sources of ultraviolet (100 ... 380 nm) and infrared (780 ... 106 nm) radiation, as well as sources of photosynthetically active radiation (400 ... 700 nm) are widely used.
According to the distribution of the optical radiation flux between different areas of the ultraviolet spectrum, sources of general ultraviolet (100 ... 380 nm), vital (280 ... 315 nm) and predominantly bactericidal (100 ... 280 nm) action are distinguished.
Sources of total ultraviolet radiation- high-pressure arc mercury tubular lamps of the DRT type (mercury-quartz lamps). A DRT lamp is a quartz glass tube with tungsten electrodes soldered into its ends. A dosed amount of mercury and argon is introduced into the lamp. DRT lamps are equipped with metal holders for easy fastening to fittings. DRT lamps are produced with a power of 2330, 400, 1000 W.
Vital luminescent lamps of the LE type are made in the form of cylindrical tubes made of uviol glass, the inner surface of which is covered with a thin layer of a phosphor that emits a light flux with a wavelength of 280 ... 380 nm in the ultraviolet region of the spectrum (maximum radiation in the region of 310 ... 320 nm). In addition to the type of glass, tube diameter and phosphor composition, tubular vital lamps do not structurally differ from low-pressure tubular fluorescent lamps and are connected to the network using the same devices (choke and starter) as fluorescent lamps of the same power. LE lamps are available with a power of 15 and 20 watts. In addition, vital-illuminating fluorescent lamps have also been developed.
germicidal lamps- These are sources of short-wave ultraviolet radiation, most of which (up to 80%) falls at a wavelength of 254 nm. The design of germicidal lamps does not fundamentally differ from low-pressure tubular fluorescent lamps, but the doped glass used for their manufacture transmits radiation well in the spectral range less than 380 nm. In addition, the flask of germicidal lamps is not covered with a phosphor and has somewhat reduced dimensions (diameter and length) compared to similar general-purpose fluorescent lamps of the same power.
Bactericidal lamps are connected to the network using the same devices as fluorescent lamps.
Lamps of increased photosynthetically active radiation. These lamps are used for artificial irradiation of plants. These include low-pressure photosynthetic fluorescent lamps of the LF and LFR types (R means reflex), high-pressure arc mercury fluorescent photosynthetic lamps of the DRLF type, high-pressure metal halide arc mercury lamps of the DRF, DRI, DROT, DMCH types, arc mercury tungsten type DRV.
Luminescent photosynthetic low-pressure lamps of the LF and LFR types are similar in design to low-pressure fluorescent lamps and differ from them only in the composition of the phosphor, and, consequently, in the emission spectrum. In lamps of the LF type, a relatively high radiation density lies in the wavelength ranges of 400 ... 450 and 600 ... 700 nm, which account for the maximum spectral sensitivity of green plants.
DRLF lamps are structurally similar to DRL type lamps, but unlike the latter, they have increased radiation in the red part of the spectrum. Under the phosphor layer, DRLF lamps have a reflective coating that provides the required distribution of the radiant flux in space.
The source of infrared radiation in the simplest case can be a conventional incandescent lighting lamp. In its emission spectrum, the infrared region occupies almost 75%, and the flux of infrared rays can be increased by reducing the voltage supplied to the lamp by 10 ... 15% or by coloring the bulb in blue or red. However, the main source of infrared radiation are special infrared mirror lamps.
Infrared mirror lamps(thermal emitters) differ from conventional lighting lamps in the paraboloid shape of the bulb and the lower temperature of the filament. The relatively low temperature of the filament of thermal lamps makes it possible to shift their radiation spectrum to the infrared region and increase the average burning time to 5000 hours.
The inner part of the bulb of such lamps, adjacent to the base, is covered with a mirror layer, which makes it possible to redistribute and concentrate the emitted infrared flux in a given direction. To reduce the intensity of visible radiation, the lower part of the bulb of some infrared lamps is covered with red or blue heat-resistant varnish.
The concept of ultraviolet rays is first encountered by a 13th century Indian philosopher in his work. The atmosphere of the area he described Bhootakasha contained violet rays that cannot be seen with the naked eye.
Shortly after infrared radiation was discovered, the German physicist Johann Wilhelm Ritter began looking for radiation at the opposite end of the spectrum, with a wavelength shorter than that of violet. In 1801, he discovered that silver chloride, which decomposes under the influence of light, is faster decomposes under the action of invisible radiation outside the violet region of the spectrum. White silver chloride darkens in the light for several minutes. Different parts of the spectrum have different effects on the darkening rate. This happens most quickly before the violet region of the spectrum. It was then agreed by many scientists, including Ritter, that light consisted of three separate components: an oxidizing or thermal (infrared) component, an illuminating component (visible light), and a reducing (ultraviolet) component. At that time, ultraviolet radiation was also called actinic radiation. The ideas about the unity of the three different parts of the spectrum were first voiced only in 1842 in the works of Alexander Becquerel, Macedonio Melloni and others.
Subtypes
Degradation of polymers and dyes
Scope of application
Black light
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 glow 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.
Faux tan and "Mountain sun"
At certain dosages, artificial tanning improves the condition and appearance of human skin, promotes the formation of vitamin D. At present, photariums are popular, which in everyday life are often called solariums.
Ultraviolet in restoration
One of the main tools of experts is ultraviolet, x-ray and infrared radiation. Ultraviolet rays allow you to determine the aging of the varnish film - a fresher varnish in the ultraviolet looks darker. In the light of a large laboratory ultraviolet lamp, restored areas and handicraft signatures appear as darker spots. X-rays are delayed by the heaviest elements. In the human body, this is bone tissue, and in the picture it is white. The basis of whitewash in most cases is lead, in the 19th century zinc began to be used, and in the 20th century titanium. These are all heavy metals. Ultimately, on the film we get the image of the bleach underpainting. Underpainting is an artist's individual "handwriting", an element of his own unique technique. For the analysis of underpainting, bases of radiographs of paintings by great masters are used. Also, these pictures are used to recognize the authenticity of the picture.
Notes
- ISO 21348 Process for Determining Solar Irradiances. Archived from the original on June 23, 2012.
- Bobukh, Evgeny On the vision of animals. Archived from the original on November 7, 2012. Retrieved November 6, 2012.
- Soviet Encyclopedia
- V. K. Popov // UFN. - 1985. - T. 147. - S. 587-604.
- A. K. Shuaibov, V. S. Shevera Ultraviolet nitrogen laser at 337.1 nm in the mode of frequent repetitions // Ukrainian Physics Journal. - 1977. - T. 22. - No. 1. - S. 157-158.
- A. G. Molchanov