Ultraviolet, infrared and visible light rays. Their impact on reptiles and amphibians

Vadim Maksimov, Leading Researcher at the Sensory Information Processing Laboratory, lead author of a study published in the prestigious British journal Proceedings of the Royal Society B, told RIA Novosti about the colors in which birds, fish, humans and insects see the world.

Colors that don't exist

Different colors do not really exist - there is no such physical property. Red, green, blue objects just reflect light at slightly different wavelengths. Our brain "sees" colors, receiving a signal from visual receptors "tuned" to a certain wavelength.

The ability to distinguish colors depends on the number of types of such receptors in the retina and their "settings". The receptors responsible for color vision are called cones, but there is also a "black and white channel" - rods. They are much more sensitive, thanks to them we can navigate at dusk, when the cones are no longer working. But we cannot distinguish colors at this time.

What do people see...

Most mammals, including dogs, have two types of cones - shortwave (with a maximum sensitivity to radiation with a wavelength of 420 nanometers) and longwave (550 nanometers). However, humans and all Old World primates have three types of cones and "three-dimensional" color vision. Human cones are tuned to 420, 530 and 560 nanometers - we perceive them as blue, green and red.

"But 2% of men are also dichromats, they are called" color blind ". In fact, they are not color blind, they just have only two types of cones - a short wavelength and one of two long wavelengths. They see colors, but worse - they do not distinguish between red and green This is what colorblind people are," Maksimov said.

Unnecessary color vision

The vision of dogs has been studied by scientists since the late 19th century. In 1908, Pavlov's student Leon Orbeli, who studied conditioned reflexes in dogs, proved the almost complete absence of color vision in dogs. However, in the middle of the 20th century, American scientists discovered that in dogs there are two types of cones in the retina, "tuned" to 429 and 555 nanometers, although in a small number - only 20% of the total number of photoreceptors.

“Dogs can see colors in much the same way as color blind people. The Americans who discovered receivers in the retina saw that a dog could be taught to distinguish colors. But they still concluded that in life a dog most likely does not use color vision, since dogs are essential part of life is awake at dusk, when the cones are not working," Maksimov said.

However, he and his colleagues in the experiment were able to prove that dogs are indeed not only technically able to distinguish colors, but also use this skill in life. In the experiment, the scientists stirred food in a closed and odor-opaque box under sheets of paper dyed light blue, dark blue, light yellow, and dark yellow.

"And then we took and changed the colors of these sheets. And suddenly it turned out that the dogs do not go on light, as before, but on dark paper, but with the same color. It turned out that not brightness is important for them, but color, that is they not only can distinguish colors, but also use it in practice,” says the scientist.

4D Vision

Record holders for color vision are fish, birds and reptiles. Most species of these animals are tetrachromats, their retinas have four types of cones, and tropical mantis shrimp have 16 types of receivers.

In particular, finches have cones tuned to ultraviolet (370 nanometers), blue (445 nanometers), green (508 nanometers) and red (565 nanometers) colors. “At the same time, birds do not distinguish brightness well. They distinguish black from white, but they refuse shades of gray. And they cannot be taught at all if the stimuli differ not only in brightness, but also in color. They “cling” to color,” Maximov said.

But the ultraviolet color unknown to man is available to birds. Maximov spoke about experiments with field sparrows, which were taught to distinguish sheets of paper painted with chalk and zinc white in different shades of gray.

“Zinc white absorbs ultraviolet light, but chalk does not. For a person, this is the same white color. We teach birds to fly on zinc light sheets, then we make the “zinc” paper dark, and we make the “chalky” paper light. And we see that the bird flew on a light piece of paper , and now it starts to fly to the dark one - precisely because it sees the "ultraviolet" color," the source said.

There is no limit

Strictly speaking, there is no clear line of sight for receptors, just as they move away from "their" wavelength, they become less and less sensitive, more and more brightness is needed to "wake up" the receptor, the scientist says.

“When you experiment with vision, as you move away from the visible range, the sensitivity drops exponentially, but no matter how much you move into the infrared or ultraviolet region, it remains non-zero,” Maksimov noted.

According to him, in special conditions, in absolute darkness and after a long adaptation, a person can see "infrared light" - radiation passing through a special glass that transmits wavelengths greater than 720 nanometers. The blue cones of the human retina are "hardware" able to see ultraviolet radiation - the problem is that the cornea and the lens of the eye do not let it through.

“It happens that a person’s lenses are removed due to cataracts, in which case a person can see ultraviolet. We had an employee who saw the difference between two whites - lead and zinc. Zinc white absorbs ultraviolet, and lead reflects,” Maximov said.

Today, the question often arises about the potential danger of ultraviolet radiation and the most effective ways to protect the organ of vision.

Today, the question often arises about the potential danger of ultraviolet radiation and the most effective ways to protect the organ of vision. We have prepared a list of the most frequently asked questions about UV and answers to them.

What is ultraviolet radiation?

The spectrum of electromagnetic radiation is quite wide, but the human eye is only sensitive to a certain area called the visible spectrum, which covers the wavelength range from 400 to 700 nm. Emissions that are outside the visible range are potentially hazardous and include infrared (wavelengths greater than 700 nm) and ultraviolet (less than 400 nm). Radiation having a shorter wavelength than ultraviolet is called X-ray and γ-radiation. If the wavelength is longer than that of infrared radiation, then these are radio waves. Thus, ultraviolet (UV) radiation is electromagnetic radiation invisible to the eye, occupying the spectral region between visible and X-ray radiation within wavelengths of 100-380 nm.

What are the ranges of ultraviolet radiation?

Just as visible light can be divided into different color components that we see when a rainbow appears, so the UV range, in turn, has three components: UV-A, UV-B and UV-C, the latter being the shortest wavelength and highest energy. ultraviolet radiation with a wavelength range of 200-280 nm, however, it is mainly absorbed by the upper atmosphere. UV-B radiation has a wavelength of 280 to 315 nm and is considered medium-energy radiation that poses a danger to the human eye. UV-A radiation is the longest wavelength component of ultraviolet with a wavelength range of 315-380 nm, which has a maximum intensity by the time it reaches the Earth's surface. UV-A radiation penetrates most deeply into biological tissues, although its damaging effect is less than that of UV-B rays.

What does the name "ultraviolet" mean?

This word means "above (above) violet" and comes from the Latin word ultra ("over") and the name of the shortest radiation in the visible range - violet. Although UV radiation is not perceptible to the human eye, some animals - birds, reptiles, and insects such as bees - can see in this light. Many birds have plumage coloration that is invisible in visible light conditions, but clearly visible in ultraviolet light. Some animals are also easier to spot in ultraviolet light. Many fruits, flowers, and seeds are perceived more distinctly by the eye in this light.

Where does ultraviolet radiation come from?

Outdoors, the main source of UV radiation is the sun. As already mentioned, it is partially absorbed by the upper layers of the atmosphere. Since a person rarely looks directly at the sun, the main harm to the organ of vision occurs as a result of exposure to scattered and reflected ultraviolet radiation. Indoors, UV radiation occurs when using sterilizers for medical and cosmetic instruments, in solariums for tanning, during the use of various medical diagnostic and therapeutic devices, as well as during the curing of filling compositions in dentistry.

In solariums, UV radiation is produced to form a tan

In industry, UV radiation is generated during welding, and its level is so high that it can cause serious damage to the eyes and skin, so the use of protective equipment is prescribed as mandatory for welders. Fluorescent lamps, widely used for lighting at work and at home, also emit UV radiation, but the level of the latter is very low and does not pose a serious hazard. Halogen lamps, which are also used for lighting, produce light with a UV component. If a person is close to a halogen lamp without a protective cap or shield, the level of UV radiation can cause serious eye problems.

In industry, UV radiation is generated during welding, and its level is so high that it can cause serious damage to the eyes and skin.

What determines the intensity of exposure to ultraviolet radiation?

Its intensity depends on many factors. First, the height of the sun above the horizon varies depending on the time of year and day. In summer, during the daytime, the intensity of UV-B radiation is maximum. There is a simple rule: when your shadow is shorter than your height, then you risk receiving 50% more such radiation.

Secondly, the intensity depends on the geographic latitude: in the equatorial regions (latitude is close to 0°), the intensity of UV radiation is the highest - 2-3 times higher than in the north of Europe.
Thirdly, the intensity increases with altitude, as the layer of the atmosphere capable of absorbing ultraviolet decreases accordingly, so more of the highest energy shortwave UV radiation reaches the Earth's surface.
Fourth, the intensity of radiation is affected by the scattering power of the atmosphere: the sky appears blue to us due to the scattering of short-wavelength blue radiation in the visible range, and even shorter-wavelength ultraviolet is scattered much more strongly.
Fifth, the radiation intensity depends on the presence of clouds and fog. When the sky is clear, UV radiation is at its maximum; dense clouds reduce its level. However, transparent and sparse clouds have little effect on the level of UV radiation, the water vapor of the fog can lead to an increase in the scattering of ultraviolet. Partially cloudy and foggy weather can be perceived as colder, but the intensity of UV radiation remains almost the same as on a clear day.

When the sky is clear, UV radiation is at its highest.

Sixth, the amount of reflected ultraviolet varies depending on the type of reflective surface. So, for snow, reflection is 90% of the incident UV radiation, for water, soil and grass - about 10%, and for sand - from 10 to 25%. This must be remembered while on the beach.

What is the effect of ultraviolet radiation on the human body?

Prolonged and intense exposure to UV radiation can be harmful to living organisms - animals, plants and humans. Note that some insects see in the UV-A range, and they are an integral part of the ecological system and in some way benefit humans. The most well-known result of exposure to ultraviolet radiation on the human body is a tan, which is still a symbol of beauty and a healthy lifestyle. However, prolonged and intense exposure to UV radiation can lead to the development of skin cancers. Keep in mind that clouds don't block UV, so the lack of bright sunlight doesn't mean UV protection isn't needed. The most harmful component of this radiation is absorbed by the ozone layer of the atmosphere. The fact that the thickness of the latter has been reduced means that UV protection will become even more important in the future. According to scientists, a decrease in the amount of ozone in the Earth's atmosphere by only 1% will lead to an increase in skin cancer by 2-3%.

What is the danger of ultraviolet radiation for the organ of vision?

There are serious laboratory and epidemiological data linking the duration of exposure to ultraviolet radiation with eye diseases: pterygium, etc. Compared to the lens of an adult, the lens of a child is much more permeable to solar radiation, and 80% of the cumulative effects of exposure to ultraviolet waves accumulate in the human body until it reaches 18 -years of age. The lens is most susceptible to radiation penetration immediately after the birth of the baby: it transmits up to 95% of the incident UV radiation. With age, the lens begins to acquire a yellow tint and becomes less transparent. By age 25, less than 25% of incident ultraviolet rays reach the retina. With aphakia, the eye is deprived of the natural protection of the lens, so it is important to use UV-absorbing lenses or filters in such a situation.
It should be borne in mind that a number of medications have photosensitizing properties, that is, they increase the effects of exposure to ultraviolet radiation. Opticians and optometrists need to have an understanding of a person's general condition and the drugs they are using in order to make recommendations about the use of protective equipment.

What kind of eye protection is available?

The most effective way to protect against ultraviolet radiation is to cover your eyes with special goggles, masks, shields that completely absorb UV radiation. In production where UV radiation sources are used, the use of such products is mandatory. When outdoors on a bright sunny day, it is recommended to wear sunglasses with special lenses that reliably protect against UV radiation. Such goggles should have wide temples or a snug fit to prevent radiation from entering from the side. Colorless spectacle lenses can also perform this function if absorbent additives are added to their composition or a special surface treatment is carried out. Well-fitting sunglasses protect both from direct incident radiation and from scattered and reflected from various surfaces. The effectiveness of the use of sunglasses and recommendations for their use are determined by indicating the category of filter, the light transmission of which corresponds to spectacle lenses.

The most effective way to protect against ultraviolet radiation is to cover your eyes with special goggles, masks that completely absorb UV radiation.

What standards govern the light transmission of sunglasses lenses?

Currently, in our country and abroad, regulatory documents have been developed that regulate the light transmission of sun lenses according to the categories of filters and the rules for their use. In Russia, this is GOST R 51831-2001 “Sunglasses. General technical requirements”, and in Europe - EN 1836: 2005 “Personal eye protection - Sunglasses for general use and filters for direct observation of the sun”.

Each type of sun lens is designed for specific lighting conditions and can be assigned to one of the filter categories. There are five of them in total, and they are numbered from 0 to 4. According to GOST R 51831-2001, the light transmission T,  %, of sun lenses in the visible region of the spectrum can range from 80 to 3-8  %, depending on the filter category. For the UV-B range (280-315 nm), this indicator should not exceed 0.1T (depending on the filter category, it can be from 8.0 to 0.3-0.8%), and for UV-A - radiation (315-380 nm) - no more than 0.5T (depending on the filter category - from 40.0 to 1.5-4.0%). At the same time, manufacturers of high-quality lenses and eyeglasses set more stringent requirements and guarantee the consumer a complete cutoff of ultraviolet radiation up to a wavelength of 380 nm or even up to 400 nm, as evidenced by special markings on glasses lenses, their packaging or accompanying documentation. It should be noted that for sunglasses lenses, the effectiveness of UV protection cannot be unequivocally determined by the degree of their darkening or the cost of glasses.

Is it true that ultraviolet light is more dangerous if a person wears low-quality sunglasses?

It really is. Under natural conditions, when a person does not wear glasses, his eyes automatically react to the excessive brightness of sunlight by changing the size of the pupil. The brighter the light, the smaller the pupil, and with a proportional ratio of visible and ultraviolet radiation, this protective mechanism works very effectively. If a darkened lens is used, the light appears less bright and the pupils enlarge, allowing more light to reach the eyes. In the event that the lens does not provide adequate protection against ultraviolet (the amount of visible radiation decreases more than ultraviolet), the total amount of ultraviolet entering the eye is more significant than in the absence of sunglasses. That is why tinted and light-absorbing lenses must contain UV absorbers, which would reduce the amount of UV radiation in proportion to the decrease in visible spectrum radiation. According to international and domestic standards, the light transmission of sun lenses in the UV region is regulated as proportionally dependent on the light transmission in the visible part of the spectrum.

Which optical material for spectacle lenses provides UV protection?

Some spectacle lens materials provide UV absorption due to their chemical structure. It activates photochromic lenses, which, under appropriate conditions, block its access to the eye. Polycarbonate contains groups that absorb radiation in the ultraviolet region, so it protects the eyes from ultraviolet radiation. CR-39 and other organic spectacle lens materials in their pure form (without additives) transmit some UV radiation, and special absorbers are introduced into their composition for reliable eye protection. These components not only protect the eyes of users by cutting off ultraviolet light up to 380 nm, but also prevent photo-oxidative degradation of organic lenses and their yellowing. Mineral spectacle lenses made from ordinary crown glass are unsuitable for reliable protection against UV radiation, unless special additives are added to the mixture for its production. Such lenses can only be used as sunscreens after high-quality vacuum coatings have been applied.

Is it true that the effectiveness of UV protection for photochromic lenses is determined by their light absorption in the activated stage?

Some users of eyeglasses ask a similar question, as they are worried about whether they will be reliably protected from ultraviolet radiation on an overcast day when there is no bright sunlight. It should be noted that modern photochromic lenses absorb from 98 to 100% of UV radiation at any light level, that is, regardless of whether they are currently colorless, medium or dark colored. This feature makes photochromic lenses suitable for spectacle wearers who are outdoors in a variety of weather conditions. There are now a growing number of people who are beginning to understand the dangers of long-term UV exposure to eye health, and many are opting for photochromic lenses. The latter are distinguished by high protective properties combined with a special advantage - automatic change in light transmission depending on the level of illumination.

Are dark-colored lenses a guarantee of UV protection?

By itself, the intense coloring of sun lenses does not guarantee UV protection. It should be noted that low-cost organic sunglass lenses produced in large-scale production can have a fairly high level of protection. Generally, a special UV absorber is first mixed with lens raw materials to make colorless lenses, and then tinted. Achieving UV protection with mineral sunglass lenses is more difficult, as their glass transmits more radiation than many types of polymer materials. For guaranteed protection, it is necessary to introduce a number of additives into the mixture for the production of lens blanks and to use additional optical coatings.
Tinted prescription lenses are made from appropriate colorless lenses, which may or may not have sufficient UV absorber to reliably cut off the appropriate range of radiation. If you need lenses with 100% UV protection, the task of controlling and ensuring such an indicator (up to 380-400 nm) is assigned to the optician-consultant and the master spectacle assembler. In this case, the introduction of UV absorbers into the surface layers of organic spectacle lenses is carried out using a technology similar to the coloring of lenses in dye solutions. The only exception is that UV protection is not visible to the eye and requires special devices - UV testers - to check it. Manufacturers and suppliers of equipment and dyes for coloring organic lenses include a variety of surface treatment formulations that provide different levels of protection against ultraviolet and short-wave visible radiation. It is not possible to control the light transmission of the ultraviolet component in a standard optical workshop.

Should an UV absorber be added to clear lenses?

Many experts believe that incorporating a UV absorber into colorless lenses will only be beneficial, as it will protect the wearer's eyes and prevent deterioration of the properties of the lenses under the influence of UV radiation and atmospheric oxygen. In some countries where there is a high level of solar radiation, such as Australia, this is mandatory. As a rule, they try to cut off radiation up to 400 nm. Thus, the most dangerous and high-energy components are excluded, and the remaining radiation is sufficient for the correct perception of the color of objects in the surrounding reality. If the cutting edge is shifted to the visible region (up to 450 nm), then the lenses will have a yellow color, with an increase to 500 nm - orange.

How can you be sure your lenses provide UV protection?

There are many different UV testers on the optical market that allow you to check the light transmission of spectacle lenses in the ultraviolet range. They show what level of transmission a given lens has in the UV range. However, it should also be taken into account that the optical power of the corrective lens can affect the measurement data. More accurate data can be obtained using complex instruments - spectrophotometers, which not only show light transmission at a certain wavelength, but also take into account the optical power of the correcting lens when measuring.

UV protection is an important aspect to consider when fitting new eyeglass lenses. We hope that the answers given in this article to questions about ultraviolet radiation and ways to protect against it will help you choose spectacle lenses that will make it possible to maintain the health of your eyes for many years to come.

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 “Entertaining 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

The energy of the Sun is electromagnetic waves, which are divided into several parts of the spectrum:

• x-rays - with the shortest wavelength (below 2 nm);
• the wavelength of ultraviolet radiation is from 2 to 400 nm;
• the visible part of the light that is captured by the eye of humans and animals (400-750 nm);
• warm oxidizing (over 750 nm).

Each part finds its application and is of great importance in the life of the planet and all its biomass. We will consider what rays are in the range from 2 to 400 nm, where they are used and what role they play in people's lives.

History of the discovery of UV radiation

The first mentions date back to the 13th century in the descriptions of a philosopher from India. He wrote about the invisible violet light that he discovered. However, the technical capabilities of that time were clearly not enough to confirm this experimentally and study it in detail.

It was possible five centuries later, a physicist from Germany, Ritter. It was he who conducted experiments on silver chloride on its decay under the influence of electromagnetic radiation. The scientist saw that this process was faster not in that region of the world, which had already been discovered by that time and was called infrared, but in the opposite one. It turned out that this is a new area, still not explored.

Thus, in 1842, ultraviolet radiation was discovered, the properties and application of which subsequently underwent a thorough analysis and study by various scientists. A great contribution to this was made by such people as: Alexander Becquerel, Warsawer, Danzig, Macedonio Melloni, Frank, Parfenov, Galanin and others.

general characteristics

What is the application of which today is so widespread in various branches of human activity? Firstly, it should be noted that this light appears only at very high temperatures from 1500 to 2000 0 C. It is in this range that UV reaches its peak activity in terms of exposure.

By physical nature, this is an electromagnetic wave, the length of which varies over a fairly wide range - from 10 (sometimes from 2) to 400 nm. The entire range of this radiation is conditionally divided into two areas:

1. near spectrum. It reaches the Earth through the atmosphere and the ozone layer from the Sun. Wavelength - 380-200 nm.
2. Far (vacuum). It is actively absorbed by ozone, air oxygen, atmospheric components. It is possible to explore only with special vacuum devices, for which it got its name. Wavelength - 200-2 nm.

There is a classification of species that have ultraviolet radiation. Properties and application finds each of them.

1. Near.
2. Further.
3. Extreme.
4. Average.
5. Vacuum.
6. Long wavelength black light (UV-A).
7. Shortwave germicidal (UV-C).
8. Medium wave UV-B.

Each species has its own wavelength of ultraviolet radiation, but they are all within the general limits already indicated earlier.

UV-A, or the so-called black light, is interesting. The fact is that this spectrum has a wavelength of 400-315 nm. This is on the border with visible light, which the human eye is able to capture. Therefore, such radiation, passing through certain objects or tissues, is capable of moving into the region of visible violet light, and people distinguish it as black, dark blue or dark purple.

The spectra produced by ultraviolet radiation sources can be of three types:

• ruled;
• continuous;
• molecular (band).

The first are characteristic of atoms, ions, gases. The second group is for recombination, bremsstrahlung radiation. Sources of the third type are most often encountered in the study of rarefied molecular gases.

Sources of ultraviolet radiation

The main sources of UV rays fall into three broad categories:

• natural or natural;
• artificial, man-made;
• laser.

The first group includes the only type of concentrator and emitter - the Sun. It is the celestial body that gives the most powerful charge of this type of waves, which are able to pass through and reach the surface of the Earth. However, not in its entirety. Scientists put forward the theory that life on Earth originated only when the ozone screen began to protect it from excessive penetration of harmful UV radiation in high concentrations.

It was during this period that protein molecules, nucleic acids and ATP became able to exist. Until today, the ozone layer enters into close interaction with the bulk of UV-A, UV-B and UV-C, neutralizing them and preventing them from passing through. Therefore, protection from ultraviolet radiation of the entire planet is exclusively his merit.

What determines the concentration of ultraviolet radiation penetrating the Earth? There are several main factors:

• ozone holes;
• height above sea level;
• solstice height;
• atmospheric dispersion;
• the degree of reflection of rays from earth's natural surfaces;
• cloud vapor state.

The range of ultraviolet radiation penetrating the Earth from the Sun ranges from 200 to 400 nm.

The following sources are artificial. These include all those devices, devices, technical means that were designed by man to obtain the desired spectrum of light with given wavelength parameters. This was done in order to obtain ultraviolet radiation, the use of which can be extremely useful in various fields of activity. Artificial sources include:

1. Erythema lamps that have the ability to activate the synthesis of vitamin D in the skin. This prevents and cures rickets.
2. Devices for solariums, in which people get not only a beautiful natural tan, but are also treated for diseases that occur when there is a lack of open sunlight (the so-called winter depression).
3. Attractant lamps that allow you to fight insects indoors safely for humans.
4. Mercury-quartz devices.
5. Excilamp.
6. Luminous devices.
7. Xenon lamps.
8. gas discharge devices.
9. High temperature plasma.
10. Synchrotron radiation in accelerators.

Another type of source is lasers. Their work is based on the generation of various gases - both inert and not. Sources can be:

• nitrogen;
• argon;
• neon;
• xenon;
• organic scintillators;
• crystals.

More recently, about 4 years ago, a free electron laser was invented. The length of ultraviolet radiation in it is equal to that observed in vacuum conditions. UV laser suppliers are used in biotechnology, microbiological research, mass spectrometry and so on.

Biological effects on organisms

The effect of ultraviolet radiation on living beings is twofold. On the one hand, with its deficiency, diseases can occur. This became clear only at the beginning of the last century. Artificial irradiation with special UV-A in the required norms is capable of:

• activate the immune system;
• cause the formation of important vasodilating compounds (histamine, for example);
• strengthen the musculoskeletal system;
• improve lung function, increase the intensity of gas exchange;
• affect the speed and quality of metabolism;
• increase the tone of the body by activating the production of hormones;
• increase the permeability of the walls of blood vessels on the skin.

If UV-A enters the human body in sufficient quantities, then it does not develop diseases such as winter depression or light starvation, and the risk of developing rickets is also significantly reduced.

The effect of ultraviolet radiation on the body is of the following types:

• bactericidal;
• anti-inflammatory;
• regenerating;
• painkiller.

These properties largely explain the widespread use of UV in medical institutions of any type.

However, in addition to the above advantages, there are also negative aspects. There are a number of diseases and ailments that can be acquired if you do not get enough or, on the contrary, take the considered waves in excess.

1. Skin cancer. This is the most dangerous exposure to ultraviolet radiation. Melanoma can form with excessive influence of waves from any source - both natural and man-made. This is especially true for lovers of tanning in the solarium. In everything, measure and caution are necessary.
2. Destructive effect on the retina of the eyeballs. In other words, a cataract, pterygium, or sheath burn may develop. The harmful excessive effects of UV on the eyes have been proven by scientists for a long time and confirmed by experimental data. Therefore, when working with such sources, you should observe. On the street, you can protect yourself with the help of dark glasses. However, in this case, you should be wary of fakes, because if the glasses are not equipped with UV-repellent filters, then the destructive effect will be even stronger.
3. Burns on the skin. In the summer, they can be earned if you expose yourself to UV for a long time uncontrollably. In winter, you can get them because of the peculiarity of the snow to reflect these waves almost completely. Therefore, irradiation occurs both from the side of the Sun and from the side of snow.
4. Aging. If people are exposed to UV for a long time, then they begin to show signs of skin aging very early: lethargy, wrinkles, sagging. This is due to the fact that the protective barrier functions of the integument are weakened and violated.
5. Impact with consequences over time. They consist in manifestations of negative influences not at a young age, but closer to old age.

All of these results are consequences of misdosing UV, ie. they occur when the use of ultraviolet radiation is carried out irrationally, incorrectly, and without observing safety measures.

Ultraviolet radiation: application

The main areas of use are based on the properties of the substance. This is also true for spectral wave radiation. So, the main characteristics of UV, on which its application is based, are:

• high level chemical activity;
• bactericidal effect on organisms;
• the ability to cause the glow of various substances in different shades visible to the human eye (luminescence).

This allows wide use of ultraviolet radiation. Application is possible in:

• spectrometric analyses;
• astronomical research;
• medicine;
• sterilization;
• disinfection of drinking water;
• photolithography;
• analytical study of minerals;
• UV filters;
• for catching insects;
• to get rid of bacteria and viruses.

Each of these areas uses a specific type of UV with its own spectrum and wavelength. Recently, this type of radiation has been actively used in physical and chemical research (determination of the electronic configuration of atoms, the crystal structure of molecules and various compounds, work with ions, analysis of physical transformations on various space objects).

There is another feature of the effect of UV on substances. Some polymeric materials are capable of decomposing under the influence of an intense constant source of these waves. For example, such as:

• polyethylene of any pressure;
• polypropylene;
• polymethyl methacrylate or organic glass.

What is the impact? Products made from these materials lose color, crack, fade, and eventually collapse. Therefore, they are called sensitive polymers. This feature of carbon chain degradation under solar illumination conditions is actively used in nanotechnologies, X-ray lithography, transplantology, and other fields. This is done mainly to smooth out the surface roughness of the products.

Spectrometry is a major field of analytical chemistry that specializes in identifying compounds and their composition by their ability to absorb UV light of a specific wavelength. It turns out that the spectra are unique for each substance, so they can be classified according to the results of spectrometry.

Also, the use of ultraviolet germicidal radiation is carried out to attract and destroy insects. The action is based on the ability of the insect's eye to capture short-wave spectra invisible to humans. Therefore, animals fly to the source, where they are destroyed.

Use in solariums - special installations of vertical and horizontal type, in which the human body is exposed to UV-A. This is done to activate the production of melanin in the skin, giving it a darker color, smoothness. In addition, inflammation is dried and harmful bacteria on the surface of the integument are destroyed. Particular attention should be paid to protecting the eyes and sensitive areas.

medical field

The use of ultraviolet radiation in medicine is also based on its ability to destroy living organisms invisible to the eye - bacteria and viruses, and on the features that occur in the body during competent lighting with artificial or natural radiation.

The main indications for UV treatment can be summarized in several points:

1. All types of inflammatory processes, open wounds, suppuration and open seams.
2. With injuries of tissues, bones.
3. For burns, frostbite and skin diseases.
4. With respiratory ailments, tuberculosis, bronchial asthma.
5. With the emergence and development of various types of infectious diseases.
6. With ailments accompanied by severe pain, neuralgia.
7. Diseases of the throat and nasal cavity.
8. Rickets and trophic
9. Dental diseases.
10. Regulation of blood pressure, normalization of the heart.
11. The development of cancerous tumors.
12. Atherosclerosis, kidney failure and some other conditions.

All these diseases can have very serious consequences for the body. Therefore, treatment and prevention using UV is a real medical discovery that saves thousands and millions of human lives, preserving and restoring their health.

Another option for using UV from a medical and biological point of view is the disinfection of premises, the sterilization of work surfaces and tools. The action is based on the ability of UV to inhibit the development and replication of DNA molecules, which leads to their extinction. Bacteria, fungi, protozoa and viruses are killed.

The main problem when using such radiation for sterilization and disinfection of a room is the area of ​​illumination. After all, organisms are destroyed only with the direct impact of direct waves. Everything that remains outside continues to exist.

Analytical work with minerals

The ability to induce luminescence in substances makes it possible to use UV to analyze the qualitative composition of minerals and valuable rocks. In this regard, precious, semi-precious and ornamental stones are very interesting. What kind of shades they do not give when irradiated with cathode waves! Malakhov, the famous geologist, wrote about this very interestingly. His work tells about observations of the glow of the color palette, which minerals can give in different sources of radiation.

So, for example, topaz, which has a beautiful saturated blue color in the visible spectrum, glows bright green when irradiated, and emerald - red. Pearls cannot give any particular color at all and shimmers with many colors. The resulting spectacle is simply fantastic.

If the composition of the studied rock contains uranium impurities, then the highlight will show a green color. Melite impurities give a blue, and morganite - a lilac or pale purple hue.

Use in filters

For use in filters, ultraviolet germicidal radiation is also used. The types of such structures can be different:

• hard;
• gaseous;
• liquid.

Such devices are mainly used in the chemical industry, in particular, in chromatography. With their help, it is possible to conduct a qualitative analysis of the composition of a substance and identify it by belonging to a particular class of organic compounds.

Drinking water treatment

Disinfection of drinking water with ultraviolet radiation is one of the most modern and high-quality methods of its purification from biological impurities. The advantages of this method are:

• reliability;
• efficiency;
• the absence of foreign products in the water;
• safety;
• profitability;
• preservation of the organoleptic properties of water.

That is why today this method of disinfection keeps pace with traditional chlorination. The action is based on the same features - the destruction of the DNA of harmful living organisms in the composition of water. Use UV with a wavelength of about 260 nm.

In addition to direct impact on pests, ultraviolet light is also used to destroy the remains of chemical compounds that are used to soften and purify water: such as, for example, chlorine or chloramine.

black light lamp

Such devices are equipped with special emitters capable of producing waves of great length, close to visible. However, they still remain indistinguishable to the human eye. Such lamps are used as devices that read secret signs from UV: for example, in passports, documents, banknotes, and so on. That is, such marks can be distinguished only under the action of a certain spectrum. Thus, the principle of operation of currency detectors, devices for checking the naturalness of banknotes is built.

Restoration and determination of the authenticity of the painting

And in this area finds application UV. Each artist used white, containing different heavy metals in each epochal period of time. Thanks to irradiation, it is possible to obtain so-called underpaintings, which provide information about the authenticity of the painting, as well as about the specific technique, manner of painting of each artist.

In addition, the lacquer film on the surface of products belongs to sensitive polymers. Therefore, it is capable of aging under the influence of light. This allows you to determine the age of compositions and masterpieces of the artistic world.

To benefit from the world around you and avoid its dangers, you need to know at least something about this world. Therefore, even primitive sedentary animals, motionless and identical on all sides, have sensitive cells or entire organs. They collect data about the environment, and based on this data, animals perform the most appropriate actions.

Organisms have learned to distinguish light from darkness a very long time ago. For many animals, including humans, vision is the main source of information about the world around them. How is this process arranged?

In the first approximation, the eyes of vertebrates and cephalopods (one of the most advanced creatures in the branch of evolution “parallel” with us) are designed like a camera. There is a lens (crystalline lens), there is a hole through which light enters the lens (pupil). Finally, there is a photographic plate (or a matrix for modern cameras) - the retina. Sensitive cells (photoreceptors) in its composition are activated when light of a certain wavelength falls. Each type of retinal cell has its own range of optimal wavelengths.

The eye is a very complex structure, and for full vision it is necessary that all its elements work well. Photo: Alexilus/shutterstock

There are two large groups of photoreceptors - rods and cones. The sticks are easy to activate, it does not require strong illumination. But the clarity of the image they give weak. This is easy to verify if you go into the forest at night without a flashlight: something is visible, but only in general terms. It is also completely incomprehensible what color the surrounding objects are. Cones are needed to recognize colors and their shades. These receptors are more difficult to activate and only work in good light.

Different types of cones are responsible for recognizing different colors by responding to light in a narrow range of wavelengths. Therefore, it is meaningless to have any one type of cones: "stick twilight" will simply acquire one or another shade. This is impractical and dangerous: with such vision, for example, it will be impossible to distinguish ripe fruits from unripe ones, and unripe fruits can be poisonous. So sighted animals have acquired at least two types of cones.

“A person has three types of cones and one type of rods,” explains Pavel Maksimov, Candidate of Biological Sciences, Senior Researcher at the Laboratory for Sensory Information Processing, IPTP RAS. “Even if we had only one type of cones and rods, we might be able to distinguish colors, but only in twilight lighting, in which both rods and cones function. In addition to the receptors themselves, appropriate signal processing is needed. For example, if signals from different types of receptors are simply added together, no color information will remain. The visual system must be able to compare signals from different receptors in order to determine whether the signal from the short-wavelength (“blue”) cones is stronger or weaker than from the long-wavelength (“red”) ones.”

Rods (left) and cones are very small: their length does not exceed 0.06 millimeters. Photo: designua/shutterstock

Cones and evolution

If an animal focuses mainly on sight, it would be good for it to be able to distinguish between many different shades, and this requires more than two types of cones.

Male and female

Despite the fact that the topic of gender equality has become very fashionable, in terms of the perception of colors, men and women differ markedly. For example, color vision disorders are more common in men. And the point here is not only that the genes, mutations in which cause the loss of some type of cones, are located on the X chromosome, which is one for the stronger sex.

The perception of colors, like sounds, depends on the level of testosterone in the body. The most feminine men have many times more receptors for this hormone than the strongest women. And in particular, there are a lot of them on the neurons of the brain, especially in the occipital lobe of the cortex - where visual signals come. As a result, in men, more connections are formed between the neurons of the visual cortex and the visual zones of the thalamus, from where the signals enter the occipital lobes. In addition, for reasons that are not completely clear, men are better at tracking small details that quickly replace each other, and women are better at distinguishing shades of close colors. Perhaps these features developed in men due to the fact that in ancient society they were engaged in hunting, and women gathered plants and mushrooms.

Hunting required ancient men to be able to discern fast-moving details. Photo: Dieter Hawlan/shutterstock

A 2001 study showed that among women, individuals with four (rather than three) types of pigments, the molecules that underlie the work of cones, are much more common among women (rods also have pigments, but others). This is one of the reasons why, on average, a woman can name more different shades than a man. Finally, the cones of men are tuned to light of slightly longer wavelengths than the visual receptors of women: apparently, the stronger sex, all other things being equal, sees the world more red.

color therapy

This branch of alternative medicine teaches that various diseases, up to and including cancer, can be treated by having the patient look at a certain color depending on what hurts. Here are just recommendations for treatment in many clinics are different, there is no general standard. And this is the first bell that color therapy is an untested method. Of course, the colors that a person sees regularly can affect his emotions and perception of the world. But this is true for any other elements of the environment. A change in mood is not yet a cure, although a thing in most cases is useful.

Some psychologists actively use color therapy in practice, but there is no serious scientific justification for this approach. Photo: Olimpik/shutterstock

Although the visual system is one of the most well-studied sensory systems, it is not easy to assess how color perception has changed over the course of evolution and how it differs between animal species and within species. We have to take into account the number of different types of visual pigments, and the structure of the retina and visual areas of the brain, and gender, and even the native language - if we are talking about people. Verbal descriptions of the same subject under the same lighting from different authors may differ markedly. And if you test color vision without resorting to words (for example, select a “special square” from dozens of identical ones), it turns out that two people can distinguish two colors, but we will never know what exactly they see in this case. And of course, the neural signals that arise in the brain in response to any color are completely individual.

Svetlana Yastrebova