The life of people, plants and animals is in close connection with the Sun. It emits radiation with special properties. Ultraviolet is considered irreplaceable and vital. With its lack, extremely undesirable processes begin in the body, and a strictly dosed amount can cure serious illnesses.
Therefore, many people need an ultraviolet lamp for home use. Let's talk about how to choose it correctly.
Ultraviolet radiation is called invisible to humans, occupying the area between the X-ray and visible spectrum. The wavelengths of its constituent waves are in the range from 10 to 400 nanometers. Physicists conventionally divide the ultraviolet spectrum into near and far, and also distinguish three types of its constituent rays. Radiation C is referred to as harsh; with a relatively long exposure, it is capable of killing living cells.
In nature, it practically does not occur, except high in the mountains. But it can be obtained in artificial conditions. Radiation B is considered average in terms of hardness. It is this that affects people in the middle of a hot summer day. Can cause harm if used excessively. And, finally, the softest and most useful - rays of type A. They are even capable of curing a person from certain diseases.
Ultraviolet is widely used in medicine and other fields. First of all, because in its presence, the body produces vitamin D, which is necessary for the normal development of the child and the health of adults. This element makes bones stronger, enhances immunity and enables the body to properly assimilate a number of essential trace elements.
In addition, doctors have proven that under the action 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, anti-miotic 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 living rays of group C, the most severe radiation
Strictly dosed beams directed to 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 state of organs after operations.
UV radiation is also widely used in cosmetology, where it is most often used to obtain sunburn and to combat certain skin problems.
Don't underestimate the UV deficiency. When it appears, a person suffers from vitamin deficiency, immunity decreases and malfunctions in the functioning of the nervous system are diagnosed. A tendency to depression and mental instability are formed. Considering all these factors, for those who wish, household versions of ultraviolet lamps for various purposes have been developed and are being produced. Let's get to know them better.
Irradiation with hard ultraviolet light for disinfection of premises has been successfully used in medicine for decades. Similar events can be carried out at home.
UV lamps: what they are
Special UV lamps are available for the normal growth of plants suffering from a lack of sunlight
It should be understood that destruction occurs only in the reach of the rays, which, unfortunately, are not able to penetrate very deeply into the wall or upholstery of upholstered furniture. To combat microorganisms, an effect of varying duration is required. Sticks and cocci tolerate it worst of all. Protozoa, spore bacteria and fungi are maximally resistant to ultraviolet light.
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 effective drying of various types of manicure gel varnish, 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. At its ends, electrodes are fixed.
When voltage is applied, an electric arc is formed between them, which evaporates the mercury, which becomes a source of powerful light energy. Depending on the design of the device, its main characteristics differ.
Quartz Emitting Devices
The bulb 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 disinfect clothes, shoes and other items very well.
You need to know that UV waves with a length of less than 257 nm activate the process of ozone formation, which is considered to be the strongest oxidizing agent. Due to this, during the disinfection process, ultraviolet light 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 during the disinfection process, animals, people and plants must be removed from the area of the lamp. Given the name of the device, they call the disinfection procedure quartzing.
It is used to disinfect hospital wards, operating rooms, catering establishments, industrial premises, etc. The simultaneous use of ozonation allows to prevent the development of pathogenic microflora and rotting, to keep the freshness of products in warehouses or shops longer. Such lamps can be used for therapeutic purposes.
Germicidal ultraviolet emitters
The main difference from the device described above is the material of the bulb. In bactericidal lamps, it is made of uviol glass. This material retains well the waves of the "hard" range, so that ozone is not generated during the operation of the equipment. Thus, disinfection is carried out only by exposure to safer soft radiation.
The UV glass from which the bactericidal lamp bulb is made completely blocks the harsh radiation. For this reason, the device is less efficient.
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 equated to them, they can function constantly. In this case, it is necessary to close the lamps with a special casing, which will direct the glow upward.
This is necessary to protect the eyes of visitors and workers. Germicidal lamps are absolutely safe for the respiratory system, since they do not emit ozone, but they are potentially harmful to the cornea of the eye. Prolonged exposure to it can lead to burns, which over time will deteriorate vision. For this reason, it is advisable to use special goggles to protect the eyes during operation of the device.
Amalgam type devices
Improved, and therefore safer in use, ultraviolet lamps. Their peculiarity lies in the fact that the mercury inside the flask is not present in a liquid, but in a bound state. It is part of the solid amalgam that covers the inside of the lamp.
Amalgam is an alloy of indium and bismuth with the addition of mercury. During the heating process, the latter begins to evaporate and emit ultraviolet light.
Inside the UV amalgam type lamps there is an alloy containing mercury. Due to the fact that the substance is bound, the device is completely safe even after damage to the bulb
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 these lamps make them safe even in the event of rough handling. If the cold flask breaks for any reason, it can simply be thrown into the nearest waste container. In the event of damage to the integrity of a burning lamp, everything is a little more complicated.
Mercury vapors will be released from it as 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 of them contains about 3 g of liquid mercury, which can be dangerous if spilled. For this reason, such lamps must be disposed of in a special way, and the place where the mercury is spilled must be treated by specialists.
Another advantage of amalgam appliances is their durability. Compared to analogs, their service life is at least twice as long. This is due to the fact that the flasks covered with amalgam from the inside do not lose their transparency. Whereas lamps with liquid mercury gradually become covered with a dense, slightly transparent coating, which significantly reduces their service life.
How not to make a mistake in choosing a device
Before deciding to buy a device, you should decide exactly whether it is really so necessary. The purchase will be perfectly justified if there is some indication. The lamp can be used for disinfection of premises, water, public goods, 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 in 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 your doctor
Therefore, doctors recommend wisely using the device in families with frequently ill children during the period of seasonal illness. The device will be useful in the process of caring for bedridden patients, since it allows not only to disinfect the room, but also helps to fight pressure sores, eliminates unpleasant odors, etc. The UV lamp can cure some diseases, but in this case it is used only on the recommendation of a doctor.
Ultraviolet light helps with inflammation of the ENT organs, dermatitis of various origins, psoriasis, neuritis, rickets, flu and colds, in the treatment of ulcers and hard-to-heal wounds, gynecological problems. Home use of UV emitters for cosmetic purposes is possible. 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 prevent them from being 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 in the room. 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 home use, manufacturers produce three types of equipment:
- Open lamps. Ultraviolet light from the source spreads 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, and then enters the room. Such lamps are not dangerous to others, therefore they can work in the presence of people.
- Specialized equipment designed to perform specific tasks. Most often it is completed with a set of tube nozzles.
Device mounting method
The manufacturer offers to choose the appropriate model from two main options: stationary and mobile. In the first case, it is envisaged to fix the device at a place selected for this. No relocations are planned. Such devices can be fixed to the ceiling or to the wall. The latter option is more in demand. A distinctive feature of stationary devices is high power, which allows you 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 recirculating lamps are produced in this design. Mobile devices are less powerful but can be easily moved to another location. These can be both closed and open lamps. The latter are especially useful for disinfecting small spaces: wardrobes, bathrooms and toilets, etc. Mobile devices are usually placed on the floor or on tables, which is quite convenient.
Moreover, floor models have great power and are quite capable of handling a room of impressive size. Most of the specialized equipment is mobile. Interesting models of UV emitters have appeared relatively recently. These are a kind of hybrids of a lamp and a germicidal lamp with two two operating modes. They work as lighting fixtures or decontaminate a room.
UV emitter power
For proper use of the UV lamp, it is important that its wattage matches the size of the room in which it will be used. The manufacturer usually indicates in the technical data sheet of the product the so-called "room coverage". This is the area 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 with a volume of up to 65 cubic meters. m, a 15 W device will be enough. This means that such a lamp can be safely purchased if the area of the treated rooms is from 15 to 35 square meters. m with a height of no more than 3 m. More powerful specimens, issuing 36 W, need to 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 UV emitters intended for home use is quite wide. Domestic manufacturers produce high-quality, efficient and quite affordable equipment. Let's consider several such devices.
Various modifications of the Solnyshko apparatus
Open-type quartz emitters of various powers are produced under this brand. Most of the models are designed for disinfection of surfaces and spaces, the area of which is not more than 15 square meters. In addition, the device can be used for therapeutic irradiation of adults and children over three years of age. The device is multifunctional, therefore it is considered universal.
The Sun ultraviolet emitter is especially popular. This universal device is capable of disinfecting the space and performing therapeutic procedures for which it is equipped with a set of special attachments
The body is equipped with a special protective screen, which is used during medical procedures and is removed during disinfection of the room. Depending on the model, the equipment is equipped with a set of special attachments or tubes for various therapeutic procedures.
Compact emitters Crystal
Another sample of domestic production. It is a small mobile device. It is intended exclusively for disinfection of spaces, the volume of which does not exceed 60 cubic meters. m. These parameters correspond to a room of standard height with an area of no more than 20 square meters. m. The device is an open type lamp, therefore it 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 the zone of its action.
During the operation of the equipment, it is imperative to remove plants, animals and people from the area of its action. 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 lamp and then the equipment will work like a regular 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 case. Air is sucked into the inside of 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 are not negatively impacted.
Depending on the model, the devices can be additionally equipped with filters that trap dirt particles and dust. The equipment is mainly produced in the form of stationary devices with wall mounting, 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 the Sun 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 specific wavelength and occupies an intermediate position between the X-ray and the violet zone of visible radiation. Such radiation is invisible to the human eye. However, due to its properties, such radiation has become very widespread and is used in many fields.
Currently, many scientists are purposefully studying the effect of ultraviolet radiation on many vital processes, including metabolic, regulatory, trophic. It is known that ultraviolet radiation has a beneficial effect on the body in certain diseases and disorders, promoting treatment... That is why it is 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 prolonged exposure to sunlight.
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 they produce a lot of free radicals, adversely affecting all processes in the body.
In addition, when using ultraviolet radiation, the risk of damage to DNA chains is very high, and this can already lead to very tragic consequences and the occurrence of such terrible diseases as cancer and others.
Do you know which ones can be useful for a person? You can learn everything from our article about such properties, as well as about the properties of ultraviolet radiation, which allow it to be used in various production processes.
We also have an overview. 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 artificial ones, several types are distinguished:
- Erythema lamps (invented in the 60s, they are mainly used 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 photoariums)
- 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 their principle of operation is associated with ultraviolet radiation, which is converted in various ways into visible light.
Methods for generating ultraviolet radiation:
- Thermal radiation (used in incandescent lamps)
- Radiation generated by gases and metal vapors moving in an electric field (used in mercury and gas-discharge lamps)
- Luminescence (used in erythemal, germicidal lamps)
The use of ultraviolet radiation due to its properties
The industry produces many types of lamps for various uses 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, 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 helps to disinfect the air, especially in places where many people gather (hospitals, schools, universities, train stations, metro, large stores).
UV disinfection of water is also in great demand as it gives good results. With this method of purification, the water does not acquire an unpleasant smell and taste. This is great for water purification in fish farms, swimming pools.
The method of ultraviolet disinfection is often used when processing surgical instruments. - The ability to induce luminescence of certain substances:
Thanks to this property, forensic experts detect traces of blood on various objects. And also thanks to special paint it is possible to detect marked bills that are used in anti-corruption operations.
Application of ultraviolet light photo
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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 wavelength range λ 400-10 nm. The entire region of ultraviolet radiation is conventionally divided into near (400-200 nm) and far, or vacuum (200-10 nm); the latter 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-rays 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). UV radiation of atoms, ions or light molecules (for example, H 2) possesses a linear 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 a decrease in transparency (an 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 radiation wavelength. For example, the reflectance of freshly powdered aluminum, one of the best materials for reflective coatings in the visible spectral region, decreases sharply at λ< 90 нм (fig. 1)... The reflection of aluminum is also significantly reduced due to surface oxidation. To protect the aluminum surface from oxidation, coatings of lithium fluoride or magnesium fluoride are used. 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 to 3000 K contains a noticeable fraction of ultraviolet radiation of the continuous spectrum, 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, the industry produces mercury, hydrogen, xenon and other gas-discharge lamps, the windows of which (or the entire bulb) are made of materials transparent to ultraviolet radiation (usually 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 are 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 atmospheric components at an altitude of 30-200 km from the Earth's surface, which plays an important role in atmospheric processes. Ultraviolet radiation from stars and other cosmic bodies, in addition to absorption in the earth's atmosphere, in the 91.2-20 nm range is almost completely absorbed by interstellar hydrogen.
Ultraviolet radiation 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 detectors 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 photomultiplier tubes has also been developed - channel electron multipliers, which make it possible to create microchannel plates. In such plates, each cell is a channel electron multiplier up to 10 μm in size. Microchannel plates allow obtaining photoelectric images in ultraviolet radiation and combine the advantages of photographic and photoelectric radiation detection methods. In the study of ultraviolet radiation, various luminescent substances are also used that convert ultraviolet radiation into visible radiation. On this basis, devices for visualization of 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 also solids. UV spectra of the Sun, stars, and others carry information about the physical processes occurring in the hot regions of these space 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, resulting in various chemical reactions (oxidation, reduction, decomposition, polymerization, etc., see Photochemistry). Luminescence under the influence of ultraviolet radiation is used in the creation of fluorescent lamps, glowing paints, in luminescence analysis and in luminescence flaw detection. Ultraviolet radiation is used in forensic science to establish the identity of dyes, the authenticity of documents, and the like. In art history, ultraviolet radiation allows you to detect in the paintings traces of restorations that are not visible to the eye. (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., Zeitz E., Ultraviolet radiation, trans. from it., M., 1952; Lazarev DN, 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 radiation, M., 1967; Stolyarov KP, Chemical analysis in ultraviolet rays, M. - L., 1965; A. Baker, D. Betteridge, Photoelectron Spectroscopy, trans. from English, M., 1975.
Rice. 1. Dependences of the reflection coefficient r of the aluminum layer on the wavelength.
Rice. 2. Spectra of action of ultrasound. outl. on 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 effect of ultraviolet radiation is based on chemical changes in biopolymer molecules. These changes are caused both by their direct absorption of radiation quanta and (to a lesser extent) by radicals of water and other low-molecular compounds formed during irradiation.
Small doses of ultraviolet radiation have a beneficial effect on humans and animals - they contribute to the formation of group vitamins 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 (tan). Large doses of ultraviolet radiation can cause eye damage (photophthalmia) and skin burns. Frequent and excessive doses of ultraviolet radiation in some cases can 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 photoperiodic reaction. It has not been established whether small doses of ultraviolet radiation are useful, and all the more necessary, for seed germination, seedling development and normal vital activity of higher plants. Large doses of ultraviolet radiation are undoubtedly unfavorable for plants, as evidenced by their existing protective devices (for example, the accumulation of certain pigments, cellular mechanisms of recovery from damage).
Ultraviolet radiation has a destructive and mutagenic effect on microorganisms and cultured 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 effects 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: its constituent pyrimidine bases (mainly thymine), when absorbed by ultraviolet radiation quanta, form dimers that prevent normal DNA duplication (replication) in preparation for cell division ... This can lead to cell death or changes in their hereditary properties (mutations). Damage to biological membranes and impaired synthesis of various components of membranes and cell walls are also of a certain importance in the lethal effect of ultraviolet radiation on cells.
Most living cells can recover from damage caused by ultraviolet radiation due to their repair systems. The ability to recover from damage caused by ultraviolet radiation probably arose in the early stages of evolution and played an important role in the survival of primary organisms exposed to intense solar ultraviolet radiation.
Biological objects differ greatly in their sensitivity to ultraviolet radiation. For example, the dose of ultraviolet radiation that causes the death of 90% of cells for different strains of E. 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 also largely depends on their physiological state and cultivation conditions before and after irradiation (temperature, composition of the nutrient medium, etc.). Mutations of some genes strongly affect the sensitivity of cells to ultraviolet radiation. There are about 20 genes known in bacteria and yeast, mutations of which increase sensitivity to ultraviolet radiation. In some cases, such genes are responsible for the restoration 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 pigmentosa - is caused by mutations in genes that control dark repair.
The genetic consequences of ultraviolet irradiation of pollen from higher plants, plant and animal cells, as well as microorganisms are expressed in an increase in the frequencies of mutation of genes, chromosomes and plasmids. The frequency of mutation of individual genes, when exposed to high doses of ultraviolet radiation, can increase thousands of times compared to the natural level and reaches several percent. In contrast to the genetic effect of ionizing radiation, gene mutations under the influence of ultraviolet radiation occur relatively more often than chromosome mutations. Due to its 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 effect of ultraviolet radiation could play a significant role in the evolution of living organisms. For the use of ultraviolet radiation in medicine, see Phototherapy.
Samoilova KA, Action of ultraviolet radiation on a cell, L., 1967; Dubrov A. P, Genetic and physiological effects of ultraviolet radiation on higher plants, M., 1968; Galanin NF, Radiant energy and its hygienic value, 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 regions 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 general ultraviolet radiation- arc mercury tubular high-pressure lamps of the DRT type (mercury-quartz lamps). A DRT-type lamp is a quartz glass tube, into the ends of which tungsten electrodes are soldered. A metered amount of mercury and argon is injected into the lamp. For ease of attachment to fittings, DRT lamps are equipped with metal holders. DRT lamps are produced with a capacity of 2330, 400, 1000 W.
Vital fluorescent lamps of the LE type are made in the form of cylindrical tubes of uviol glass, the inner surface of which is covered with a thin layer of phosphor, which emits a luminous flux in the ultraviolet region of the spectrum with a wavelength of 280 ... 380 nm (maximum radiation in the region of 310 ... 320 nm). In addition to the glass type, tube diameter and phosphor composition, tubular vital lamps do not differ structurally 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 produced with a power of 15 and 20 watts. In addition, vital lighting fluorescent lamps have been developed.
Germicidal lamps- these are sources of short-wave ultraviolet radiation, most of which (up to 80%) falls on a wavelength of 254 nm. The design of bactericidal lamps does not fundamentally differ from low-pressure tubular fluorescent lamps, but the glass with dopants used for their manufacture transmits radiation well in the spectral range less than 380 nm. In addition, the bulb of germicidal lamps is not coated with a phosphor and has a slightly reduced size (diameter and length) in comparison with similar general-purpose fluorescent lamps of the same power.
Germicidal 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 luminescent photosynthetic lamps of the LF and LFR types (P stands for reflex), high-pressure mercury-arc luminescent photosynthetic lamps of the DRLF type, metal-halide high-pressure mercury arc lamps of the DRF, DRI, DROT, DMCh types, tungsten mercury arc tungsten arc types.
Low-pressure fluorescent photosynthetic 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 lamps, but unlike the latter, they have increased radiation in the red part of the spectrum. DRLF lamps have a reflective coating under the phosphor layer, which ensures the required distribution of the radiant flux in space.
In the simplest case, the source of infrared radiation can be an ordinary incandescent lamp... In its radiation spectrum, the infrared region occupies almost 75%, and it is possible to increase the flux of infrared rays by reducing the voltage supplied to the lamp by 10 ... 15% or by coloring the bulb in blue or red. However, special infrared mirror lamps are the main source of infrared radiation.
Infrared mirror lamps(thermal emitters) differ from conventional lighting lamps with a paraboloid bulb and a lower filament temperature. The relatively low temperature of the incandescent filament of thermal emitting lamps makes it possible to shift the spectrum of their radiation to the infrared region and increase the average burning time up 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 coated with a red or blue heat-resistant varnish.
The concept of ultraviolet rays was 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.
Soon after the discovery of infrared radiation, 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, decomposed by light, was faster decomposes under the influence of invisible radiation outside the violet region of the spectrum. Silver chloride, white in color, darkens in the light within a few minutes. Different parts of the spectrum have different effects on the rate of darkening. This occurs most rapidly in front of the violet region of the spectrum. It was then that many scientists, including Ritter, agreed that light is made up 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 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 the irradiation of a substance with monochromatic UV radiation, the wavelength of which changes over time. The substance absorbs UV radiation at different wavelengths to varying degrees. The graph, the ordinate of which is the amount of transmitted or reflected radiation, and the abscissa is the wavelength, forms a spectrum. Spectra are unique for each substance, which is the basis for the identification of individual substances in a mixture, as well as their quantitative measurement.
Mineral analysis
Many minerals contain substances that, when illuminated with ultraviolet light, 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. AA Malakhov in his book "Interestingly about geology" (M., "Molodaya gvardiya", 1969, 240 p.) Tells about it this way: "The unusual glow of minerals is caused by cathode, ultraviolet, and X-rays. In the world of dead stone, those minerals that light up and shine most brightly, which, once in the ultraviolet light zone, tell about the smallest impurities of uranium or manganese included in the composition of the rock. Many other minerals, which do not contain any impurities, flash with a strange "unearthly" color. I spent the whole day in the laboratory, where I observed the luminescent glow of minerals. Plain colorless calcite was colored wonderfully under the influence of various light sources. The cathode rays made the crystal ruby red; in ultraviolet light, it lit up with 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 connected, the fluorite turned violet, 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 their luminescence color and retention index.
Catching insects
Ultraviolet radiation is often used to catch insects by 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 shortwave part of the spectrum: insects do not see what a person perceives as red, but see soft ultraviolet light.
Artificial tan and "Mountain sun"
At certain dosages, artificial tanning improves the condition and appearance of human skin, promotes the formation of vitamin D. Currently, photoaria are popular, which are often called solariums in everyday life.
Ultraviolet in restoration
One of the experts' main tools is ultraviolet, X-ray and infrared radiation. Ultraviolet rays allow you to determine the aging of the varnish film - a fresher varnish looks darker in ultraviolet light. In the light of a large laboratory ultraviolet lamp, the restored areas and artisanally rewritten signatures appear darker spots. X-rays are trapped by the heaviest elements. In the human body, this is bone tissue, but in the picture it is white. In most cases, white is based on lead, in the 19th century zinc began to be used, and in the 20th century - titanium. These are all heavy metals. Ultimately, on film, we get an image of a whitewash underpainting. Underpainting is the artist's individual “handwriting”, an element of his own unique technique. To analyze the underpainting, the bases of the radiographs of the paintings of the great masters are used. Also, these pictures are used to recognize the authenticity of the painting.
Notes (edit)
- ISO 21348 Process for Determining Solar Irradiances. Archived from the original on June 23, 2012.
- Bobukh, Eugene About the eyesight 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 high repetition mode // Ukrainian physical journal... - 1977. - T. 22. - No. 1. - S. 157-158.
- A. G. Molchanov