The ultraviolet range of electromagnetic radiation lies beyond the violet (shortwave) edge of the visible spectrum.

The near ultraviolet from the Sun passes through the atmosphere. It causes sunburn on the skin and is necessary for the production of vitamin D. But excessive exposure is fraught with the development of skin cancer. UV radiation is harmful to the eyes. Therefore, on the water and especially on the snow in the mountains, it is imperative to wear goggles.

Harder UV radiation is absorbed in the atmosphere by molecules of ozone and other gases. It can only be observed from space, which is why it is called vacuum ultraviolet.

The energy of ultraviolet quanta is sufficient to destroy biological molecules, in particular DNA and proteins. This is one of the methods for the destruction of microbes. It is believed that as long as there was no ozone in the Earth's atmosphere, which absorbs a significant part of ultraviolet radiation, life could not leave the water on land.

Ultraviolet is emitted by objects with temperatures ranging from thousands to hundreds of thousands of degrees, such as young, hot, massive stars. However, UV radiation is absorbed by interstellar gas and dust, so we often see not the sources themselves, but the cosmic clouds illuminated by them.

To collect UV radiation, mirror telescopes are used, and photomultipliers are used for registration, and in the near UV, as in visible light, CCD matrices are used.

Sources

The glow is produced when charged particles in the solar wind collide with molecules in Jupiter's atmosphere. Most of the particles under the influence of the planet's magnetic field enter the atmosphere near its magnetic poles. Therefore, radiance occurs in a relatively small area. Similar processes are taking place on Earth and on other planets with an atmosphere and a magnetic field. The image was taken by the Hubble Space Telescope.

Receivers

Hubble Space Telescope

sky surveys

The survey was built by the Extreme Ultraviolet Explorer (EUVE, 1992–2001) orbital ultraviolet observatory. The line structure of the image corresponds to the orbital motion of the satellite, and the inhomogeneity of the brightness of individual bands is associated with changes in the calibration of the equipment. Black stripes are areas of the sky that could not be observed. The small number of details in this review is due to the fact that there are relatively few sources of hard ultraviolet and, in addition, ultraviolet radiation is scattered by cosmic dust.

Earth application

Installation for dosed irradiation of the body with near ultraviolet for tanning. Ultraviolet radiation leads to the release of the pigment melanin in the cells, which changes the color of the skin.

Doctors divide the near ultraviolet into three sections: UV-A (400–315 nm), UV-B (315–280 nm) and UV-C (280–200 nm). The mildest UV-A light stimulates the release of melanin stored in melanocytes, the cellular organelles where it is produced. Harder UV-B triggers the production of new melanin and also stimulates the production of vitamin D in the skin. Solarium models differ in their radiation power in these two areas of the UV range.

In the composition of sunlight near the Earth's surface, up to 99% of ultraviolet is in the UV-A region, and the rest is in UV-B. Radiation in the UV-C range has a bactericidal effect; in the solar spectrum it is much less than UV-A and UV-B, in addition, most of it is absorbed in the atmosphere. Ultraviolet radiation causes drying and aging of the skin and promotes the development of cancer. Moreover, radiation in the UV-A range increases the likelihood of the most dangerous type of skin cancer - melanoma.

UV-B radiation is almost completely blocked by protective creams, in contrast to UV-A, which penetrates through such protection and even partially through clothing. In general, it is believed that very small doses of UV-B are good for health, and the rest of the UV is harmful.

Ultraviolet radiation is used to determine the authenticity of banknotes. Polymer fibers with a special dye are pressed into banknotes, which absorbs ultraviolet quanta, and then emits less energetic visible radiation. Under the influence of ultraviolet light, the fibers begin to glow, which is one of the signs of authenticity.

The ultraviolet radiation of the detector is invisible to the eye, the blue glow that is noticeable during the operation of most detectors is due to the fact that the used ultraviolet sources also emit in the visible range.

Ultraviolet radiation Prepared by 11th grade student Vyacheslav Yumaev

Ultraviolet radiation is electromagnetic radiation invisible to the eye, occupying the region between the lower limit of the visible spectrum and the upper limit of X-ray radiation. The wavelength of UV - radiation lies in the range from 100 to 400 nm (1 nm = 10 m). According to the classification of the International Commission on Illumination (CIE), the UV spectrum is divided into three ranges: UV-A - long-wave (315 - 400 nm.) UV-B - medium-wave (280 - 315 nm.) UV-C - short-wave (100 - 280 nm.) The entire UV region is conditionally divided into: - near (400-200nm); - distant or vacuum (200-10 nm).

Properties: High chemical activity, invisible, high penetrating power, kills microorganisms, in small doses has a beneficial effect on the human body: sunburn, UV rays initiate the formation of vitamin D, which is necessary for the absorption of calcium by the body and ensuring the normal development of the bone skeleton, ultraviolet is active affects the synthesis of hormones responsible for the daily biological rhythm; but in large doses it has a negative biological effect: changes in cell development and metabolism, effects on the eyes.

Spectrum of UV radiation: line (atoms, ions and light molecules); consists of bands (heavy molecules); Continuous spectrum (appears during deceleration and recombination of electrons).

Discovery of UV radiation: Near UV 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 UV radiation was discovered by the German scientist W. Schumann using a vacuum spectrograph with a fluorite prism built by him and gelatin-free photographic plates. He was able to register short-wave radiation up to 130 nm. N. Ritter W. Wollaston

Features of UV radiation Up to 90% of this radiation is absorbed by atmospheric ozone. For every 1000m increase in altitude, UV levels increase by 12%.

Application: Medicine: the use of UV - radiation in medicine is due to the fact that it has a bactericidal, mutagenic, therapeutic (therapeutic), antimitotic, preventive action, disinfection; laser biomedicine Showbiz: Lighting, lighting effects

Cosmetology: In cosmetology, ultraviolet irradiation is widely used in solariums to obtain an even, beautiful tan. Deficiency of UV rays leads to beriberi, decreased immunity, weak functioning of the nervous system, and the appearance of mental instability. Ultraviolet radiation has a significant effect on phosphorus-calcium metabolism, stimulates the formation of vitamin D and improves all metabolic processes in the body.

Food industry: Disinfection of water, air, premises, containers and packaging by UV radiation. It should be emphasized that the use of UV radiation as a physical factor influencing microorganisms can provide a very high degree of disinfection of the environment, for example, up to 99.9%.

Forensics: Scientists have developed technology to detect the smallest doses of explosives. The device for detecting traces of explosives uses the thinnest thread (it is two thousand times thinner than a human hair), which glows under the influence of ultraviolet radiation, but any contact with explosives: trinitrotoluene or other explosives used in bombs stops its glow. The device detects the presence of explosives in the air, in water, on tissue and on the skin of suspects in a crime. Use of invisible UV inks to protect bank cards and banknotes from forgery. Images, design elements that are invisible in ordinary light, or make the entire map glow in UV rays are applied to the map.

Sources of UV radiation: emitted by all solids with t>1000 C, as well as luminous mercury vapor; stars (including the Sun); laser installations; discharge lamps with quartz tubes (quartz lamps), mercury; mercury rectifiers

Protection against UV radiation: Use of sun screens: - chemical (chemicals and topping creams); - physical (various barriers that reflect, absorb or scatter rays). Special clothing (for example, made from poplin). To protect the eyes in production conditions, light filters (glasses, helmets) made of dark green glass are used. Full protection against UV radiation of all wavelengths is provided by flint glass (glass containing lead oxide) with a thickness of 2 mm.

Thank you for your attention!

The properties of ultraviolet radiation are determined by many parameters. Ultraviolet radiation is called invisible electromagnetic radiation, which occupies a certain spectral region between X-ray and visible radiation within the respective wavelengths. The wavelength of ultraviolet radiation is 400 - 100 nm and has weak biological effects.

The higher the biological activity of the waves of this radiation, the weaker the effect, respectively, the lower the wavelength, the stronger the biological activity. Waves with a length of 280 - 200 nm have the strongest activity, which have bactericidal effects and actively affect body tissues.

The frequency of ultraviolet radiation is closely related to wavelengths, so the higher the wavelength, the lower the frequency of the radiation. The range of ultraviolet radiation reaching the Earth's surface is 400 - 280 nm, and shorter waves emanating from the Sun are absorbed even in the stratosphere with the help of ozone layer.

The area of ​​UV radiation is conditionally divided into:

• Near - from 400 to 200 nm
• Far - from 380 to 200 nm
• Vacuum - from 200 to 10 nm

The spectrum of ultraviolet radiation depends on the nature of the origin of this radiation and can be:

• Linear (radiation of atoms, light molecules and ions)
• Continuous (deceleration and recombination of electrons)
• Consisting of bands (radiation of heavy molecules)

Properties of UV radiation

The properties of ultraviolet radiation are chemical activity, penetrating power, invisibility, destruction of microorganisms, beneficial effects on the human body (in small doses) and negative effects on humans (in large doses). Properties of ultraviolet radiation in optical area have significant differences from the optical properties of the ultraviolet of the visible region. The most characteristic feature is the increase in the special absorption coefficient, which leads to a decrease in the transparency of many bodies that have transparency in visible area.

The reflection coefficient of various bodies and materials decreases taking into account the decrease in the wavelength of the radiation itself. The physics of ultraviolet radiation corresponds to modern ideas and ceases to be an independent dynamics at high energies, and is also combined into one theory with all gauge fields.

Do you know what is different for different intensities of such radiation? Read detailed information about beneficial and harmful doses of UV radiation in one of our articles.

We also have information about use in the garden. Many summer residents are already using solar panels in their homes. Try it by reading our material.

History of the discovery of ultraviolet radiation

Ultraviolet radiation, whose discovery history dates back to 1801, was announced only in 1842. This phenomenon was discovered by the German physicist Johann Wilhelm Ritter and was called " actinic radiation". This radiation was part of the individual components of light, and played the role of a reducing element.

The very concept of ultraviolet rays was first encountered in history in the 13th century, in the work of the scientist Sri Madhacharaya, who described the atmosphere of the Bhutakashi area containing violet rays invisible to human eyes.

In the course of experiments in 1801, a group of scientists found that light has several separate components: oxidizing, thermal (infrared), illuminating (visible light) and reducing (ultraviolet).

UV radiation is a continuously operating factor of the environment and has a strong impact on various physiological processes that occur in organisms.

According to scientists, it was it that played the main role in the course of evolutionary processes on Earth. Due to this factor, an abiogenic synthesis of organic terrestrial compounds occurred, which influenced the increase in the diversity of life forms.

It turned out that all living beings, in the course of evolution, have adapted to use the energy of all parts of the spectrum of solar energy. The visible part of the solar range is for photosynthesis, the infrared for heat. UV components are used as photochemical synthesis vitamin D, which plays an important role in the exchange of phosphorus and calcium in the body of living beings and humans.

The ultraviolet range is located from visible light from the short-wave side, and the rays of the near region are perceived by a person as the appearance of a tan on the skin. Short waves cause a destructive effect on biological molecules.

The ultraviolet radiation of the sun has the biological effectiveness of three spectral regions, which differ significantly from each other and have corresponding ranges that affect living organisms in different ways.

This radiation is taken for therapeutic and prophylactic purposes in certain dosages. For such medical procedures, special artificial radiation sources are used, the radiation spectrum of which consists of shorter rays, which has a more intense effect on biological tissues.

Harm from ultraviolet radiation brings a strong effect of this radiation source on the body and can cause damage mucous membranes and various skin dermatitis. Basically, damage from ultraviolet radiation is observed in workers in various fields of activity who are in contact with artificial sources of these waves.

Measurement of ultraviolet radiation is carried out by multichannel radiometers and continuous wave spectroradiometers, which are based on the use of vacuum photodiodes and photoids with a limited wavelength range.

Properties of ultraviolet radiation photo

Below are photos on the topic of the article "Properties of ultraviolet radiation." To open the photo gallery, just click on the image thumbnail.

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

1. ISO 21348 Process for Determining Solar Irradiances. Archived from the original on June 23, 2012.
2. Bobukh, Evgeny On the vision of animals. Archived from the original on November 7, 2012. Retrieved November 6, 2012.
3. Soviet Encyclopedia
4. V. K. Popov // UFN. - 1985. - T. 147. - S. 587-604.
5. 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.
6. A. G. Molchanov

General characteristics of ultraviolet radiation

Remark 1

Ultraviolet radiation opened I.V. Ritter in $1842$. Subsequently, the properties of this radiation and its application were subjected to the most thorough analysis and study. Such scientists as A. Becquerel, Warsawer, Danzig, Frank, Parfenov, Galanin and many others made a great contribution to this study.

Currently ultraviolet radiation widely used in various fields of activity. The peak of ultraviolet activity reaches in the range of high temperatures. This kind of spectrum appears when the temperature reaches $1500$ to $20000$ degrees.

Conventionally, the radiation range is divided into 2 areas:

1. near spectrum, which reaches the Earth from the Sun through the atmosphere and has a wavelength of $380$-$200$ nm;
2. far spectrum absorbed by ozone, atmospheric oxygen and other components of the atmosphere. This spectrum can be studied using special vacuum devices, so it is also called vacuum. Its wavelength is $200$-$2$ nm.

Ultraviolet radiation can be near, far, extreme, medium, vacuum, and each of its types has its own properties and finds its application. Each type of ultraviolet radiation has its own wavelength, but within the limits indicated above.

Spectrum of ultraviolet rays of the sun reaching the Earth's surface is narrow - $400$…$290$ nm. It turns out that the Sun does not emit light with a wavelength shorter than $290$ nm. So is it or isn't it? The answer to this question was found by the French A. Cornu who found that ultraviolet rays shorter than $295$ nm are absorbed by ozone. Based on this, A. Cornu suggested that the sun emits short-wavelength ultraviolet radiation. Oxygen molecules under its action break down into individual atoms and form ozone molecules. Ozone covers the planet in the upper atmosphere protective screen.

Scientist's assumption confirmed when a person managed to rise into the upper layers of the atmosphere. The height of the sun above the horizon and the amount of ultraviolet rays reaching the earth's surface are directly related. When the illumination changes by $20$%, the number of ultraviolet rays reaching the surface will decrease by $20$ times. The experiments performed showed that for every $100$ m of ascent, the intensity of ultraviolet radiation increases by $3$-$4$ %. In the equatorial region of the planet, when the Sun is at its zenith, the earth's surface is reached by rays with a length of $290$…$289$ nm. Beams with a wavelength of $350$…$380$ nm arrive at the earth's surface beyond the Arctic Circle.

Sources of ultraviolet radiation

Ultraviolet radiation has its sources:

1. Natural sources;
2. Sources created by man;
3. laser sources.

natural source ultraviolet rays is their only concentrator and emitter - this is our The sun. The closest star to us emits a powerful charge of waves that can pass through the ozone layer and reach the earth's surface. Numerous studies have allowed scientists to put forward the theory that only with the advent of the ozone layer on the planet could life arise. It is this layer that protects all living things from harmful excessive penetration of ultraviolet radiation. The ability to exist of protein molecules, nucleic acids and ATP became possible during this period. Ozone layer performs a very important function, interacting with the bulk UV-A, UV-B, UV-C, it neutralizes them and does not let them to the surface of the Earth. The ultraviolet radiation reaching the earth's surface has a range that ranges from $200$ to $400$ nm.

The concentration of ultraviolet on Earth depends on a number of factors:

1. The presence of ozone holes;
2. Position of the territory (height) above sea level;
3. The height of the Sun itself;
4. The ability of the atmosphere to scatter rays;
5. The reflectivity of the underlying surface;
6. Cloud vapor states.

artificial sources ultraviolet light is usually created by man. It can be devices, devices, technical means designed by people. They are created to obtain the desired spectrum of light with given wavelength parameters. The purpose of their creation is that the resulting ultraviolet radiation can be usefully applied in various fields of activity.

Artificial sources include:

1. Possessing the ability to activate the synthesis of vitamin D in human skin erythema lamps. They not only protect against rickets, but also treat this disease;
2. Special devices for solariums that prevent winter depression and give a beautiful natural tan;
3. Used indoors to control insects attractant lamps. For humans, they do not pose a danger;
4. Mercury-quartz devices;
5. excilamps;
6. Luminescent devices;
7. Xenon lamps;
8. gas discharge devices;
9. High temperature plasma;
10. Synchrotron radiation in accelerators.

Man-made sources of ultraviolet light include lasers, whose work is based on the generation of inert and non-inert gases. It can be nitrogen, argon, neon, xenon, organic scintillators, crystals. There is currently laser working on free electrons. It produces a length of ultraviolet radiation equal to that observed in vacuum conditions. Laser ultraviolet is used in biotechnological, microbiological research, mass spectrometry, etc.

Application of ultraviolet radiation

Ultraviolet radiation has such characteristics that allow it to be used in various fields.

UV characteristics:

1. High level of chemical activity;
2. bactericidal effect;
3. The ability to cause luminescence, i.e. the glow of various substances in different shades.

Based on this, ultraviolet radiation can be widely used, for example, in spectrometric analysis, astronomy, medicine, drinking water disinfection, mineral analysis, insect, bacteria and virus destruction. Each area uses a different type of UV with its own spectrum and wavelength.

Spectrometry specializes in the identification of compounds and their composition by their ability to absorb UV light of a certain wavelength. According to the results of spectrometry, the spectra for each substance can be classified, because they are unique. The destruction of insects is based on the fact that their eyes pick up short-wave spectra invisible to humans. Insects fly to this source and are destroyed. Special installations in solariums expose the human body UV-A. As a result, melanin production is activated in the skin, which gives it a darker and more even color. Here, of course, it is important to protect sensitive areas and eyes.

The medicine. The use of ultraviolet radiation in this area is also associated with the destruction of living organisms - bacteria and viruses.

Medical indications for ultraviolet treatment:

1. Injury to tissues, bones;
2. Inflammatory processes;
3. Burns, frostbite, skin diseases;
4. Acute respiratory diseases, tuberculosis, asthma;
5. Infectious diseases, neuralgia;
6. Diseases of the ear, throat, nose;
7. Rickets and trophic ulcers of the stomach;
8. Atherosclerosis, kidney failure, etc.

This is not the whole list of diseases for the treatment of which ultraviolet is used.

Remark 2

Thus, ultraviolet helps doctors save millions of human lives and restore their health. Ultraviolet is also used for disinfection of premises, sterilization of medical instruments and work surfaces.

Analytical work with minerals. Ultraviolet causes luminescence in substances and this makes it possible to use it to analyze the qualitative composition of minerals and valuable rocks. Precious, semi-precious and ornamental stones give very interesting results. When irradiated with cathode waves, they give amazing and unique shades. The blue color of topaz, for example, when irradiated, is highlighted bright green, emerald - red, pearls shimmer with multicolor. The spectacle is amazing, fantastic.