What are the rays of the sun. Sun rays. What are the benefits of the sun

Today, many people are interested in the effects of direct sunlight on the body, especially those who want to spend the summer with benefit for themselves, stock up on solar energy and get a beautiful healthy tan. What is solar radiation and what effect does it have on us?

Definition

The sun's rays (photo below) are a stream of radiation, which is represented by electromagnetic oscillations of waves of different lengths. The spectrum of radiation emitted by the sun is diverse and wide both in terms of wavelength and frequency, and in terms of its effect on the human body.

Types of sunbeams

There are several regions of the spectrum:

1. Gamma radiation.
2. X-ray radiation (wavelength - less than 170 nanometers).
3. Ultraviolet radiation (wavelength - 170-350 nm).
4. Sunlight (wavelength - 350-750 nm).
5. Infrared spectrum, which has a thermal effect (wavelengths - more than 750 nm).

In terms of biological influence on a living organism, ultraviolet rays of the sun are the most active. They contribute to the formation of tanning, have a hormone-protective effect, stimulate the production of serotonin and other important components that increase vitality and vitality.

Ultraviolet radiation

In the ultraviolet spectrum, 3 classes of rays are distinguished, which affect the body in different ways:

1. A-rays (wavelength - 400-320 nanometers). They have the lowest level of radiation; they remain constant in the solar spectrum throughout the day and year. There are almost no barriers for them. Bad influence the sun's rays of this class on the body are the lowest, however, their constant presence accelerates the process of natural aging of the skin, because, penetrating to the growth layer, they damage the structure and base of the epidermis, destroying elastin and collagen fibers.
2. B-rays (wavelength - 320-280 nm). Only at certain times of the year and hours of the day do they reach the Earth. Depending on the geographic latitude and air temperature, they usually enter the atmosphere from 10:00 to 16:00. These rays of the sun take part in the activation of the synthesis of vitamin D3 in the body, which is their main positive property. However, with prolonged exposure to the skin, they are able to change the genome of cells in such a way that they uncontrollably begin to multiply and form cancer.
3. C-rays (wavelength - 280-170 nm). This is the most dangerous part of the UV spectrum, unconditionally provoking the development of cancer. But in nature, everything is very wisely arranged, and the harmful C rays of the sun, like most (90 percent) of the B rays, are absorbed by the ozone layer before reaching the Earth's surface. So nature protects all living things from extinction.

Positive and negative impact

Depending on the duration, intensity, frequency of exposure to UV radiation, positive and negative effects develop in the human body. The former include the formation of vitamin D, the production of melanin and the formation of a beautiful, even tan, the synthesis of mediators regulating biorhythms, the production of an important regulator endocrine system- serotonin. That is why after the summer we feel a surge of strength, an increase in vitality, a good mood.

The negative effects of ultraviolet exposure are skin burns, damage to collagen fibers, the appearance of cosmetic defects in the form of hyperpigmentation, provoking cancer.

Synthesis of vitamin D

When exposed to the epidermis, the energy of solar radiation is converted into heat or spent on photochemical reactions, as a result of which various biochemical processes are carried out in the body.

Vitamin D is supplied in two ways:

• endogenous - due to the formation in the skin under the influence of UV rays B;
• exogenous - due to intake with food.

The endogenous pathway is a rather complex process of reactions that occur without the participation of enzymes, but with the mandatory participation of UV irradiation with B rays. With sufficient and regular insolation, the amount of vitamin D3 synthesized in the skin during photochemical reactions fully meets all the needs of the body.

Sunburn and vitamin D

The activity of photochemical processes in the skin directly depends on the spectrum and intensity of exposure to ultraviolet radiation and is inversely related to sunburn (degree of pigmentation). It has been proven that the more pronounced the tan, the more time it takes for the accumulation of provitamin D3 in the skin (instead of fifteen minutes, three hours).

From the point of view of physiology, this is understandable, since tanning is a protective mechanism of our skin, and the melanin layer formed in it acts as a certain barrier to both UV B rays, which serve as a mediator of photochemical processes, and class A rays, which provide the thermal stage of transformation in the skin provitamin D3 to vitamin D3.

But vitamin D supplied with food only compensates for the deficiency in case of insufficient production in the process of photochemical synthesis.

Formation of vitamin D when exposed to the sun

Today it has already been established by science that to meet the daily need for endogenous vitamin D3, it is enough to stay under open solar UV rays of class B for ten to twenty minutes. Another thing is that such rays are not always present in the solar spectrum. Their presence depends both on the season of the year and on the geographic latitude, since the Earth, during rotation, changes the thickness and angle of the atmospheric layer through which the sun's rays pass.

Therefore, the radiation of the sun is not always able to form vitamin D3 in the skin, but only when UV B rays are present in the spectrum.

Solar radiation in Russia

In our country, taking into account geographical location rich in class UV rays During periods of solar radiation are unevenly distributed. For example, in Sochi, Makhachkala, Vladikavkaz they last about seven months (from March to October), and in Arkhangelsk, St. Petersburg, Syktyvkar last about three (from May to July) or even less. Add to this the number of cloudy days a year, the smoky atmosphere in major cities, and it becomes clear that most of the inhabitants of Russia lack hormonotropic solar exposure.

This is probably why we intuitively strive for the sun and rush to the southern beaches, while forgetting that the sun's rays in the south are completely different, unusual for our body, and, in addition to burns, can provoke strong hormonal and immune surges that can increase the risk of cancer and other ailments .

At the same time, the southern sun is able to heal, just a reasonable approach must be observed in everything.

Starostin Dmitry

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MBOU "Gymnasium No. 34"

Research work

on the topic

Sunbeams: what are they?

Completed:

Starostin Dmitry,

4th grade student B

MBOU "Gymnasium No. 34"

Supervisor:

Sergeeva Irina Vyacheslavovna,

primary school teacher

Supreme QC.

2012

I Introduction ………………………………………………………………………… 3

II. Light and life - a single whole?………………………………………………… 4

III. Experiments and observations………………………………………………………... . 7

Rays of light are rectilinear……………………………………………………….. .7

Rays are refracted………………………………………………………………. .7

Where does snow melt faster? .......................................... ten

What color is the sunlight?..……………………………..……………….. 12

Colored Shadows……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Invisible light………………………………………………………………...16

IV. conclusions …………………………………………………………………………20

V. Bibliography ………………………… ………………………………….. ….21

Introduction

Target: learn about some of the properties and features of the sun's rays.

Tasks:

Find out how sunlight affects the growth and development of plants, animals and humans.

Prove that the rays of light are rectilinear, that they are refracted.

Find out why snow melts faster where there are thawed patches.

Find out what color sunlight is.

Empirically establish whether there is a color in the shadow and whether there are invisible light.

Based on the analysis of works of art, formulate the image of the Sun.

Hypothesis : assumed that sunlight is white.

In the lessons of the world around us, we learned a lot about the Sun, about its significance in the life of the planet. I was very interested this topic, and I decided to learn more about the sun's rays. To do this, I searched for information in encyclopedias, on the Internet, talked with adults, watched TV shows, conducted experiments and observations.

Light and life - a single whole?

All living organisms that exist on our planet, almost completely owe this to the Sun. Largely thanks to the Sun, the world around us was formed in such a form in which we can observe it, perhaps life on the planet would not have originated at all, or had a completely different appearance if it were otherwise located in outer space relative to the Sun. The sun and its rays play very important role in the development and existence of all forms of life on the planet, almost all its inhabitants love their light and warmth, which they generously share for millions of years, since life originated on the planet. The sun's rays are vital to all plants, animals and other inhabitants of our world, including people.

In moderate doses, the sun helps a person, under its rays, the body produces a very important vitamin D, which strengthens bones, promotes the absorption of many minerals and strengthens the immune system. Ultraviolet (UV) radiation, in small doses, can also be useful, it has an antibacterial effect. But do not abuse the consumption of sunlight, because. possible burns of the skin, as well as overheating of the whole organism.

Sunlight is also essential for the growth and development of plants and animals. In order to understand what an important role sunlight plays in wildlife, I decided to conduct the following experiment. I took two bean seeds and planted them in identical pots. I put one pot on the window, through the glass of which the sun's rays freely passed, therefore, the plant could consume light and heat in sufficient quantities. I put the second pot of bean seed in a dark closet, where the sun's rays could not penetrate. As a result of observations, it turned out that the plant on the window sprouted on the third day, and on the sixth day the first leaves appeared. What could not be said about the plant that was in the closet. There were no changes on the third or seventh day, the bean seed did not even germinate. Therefore, one can do conclusion , that the sun's rays are necessary for the growth and development of plants.

fig.1 Second day of experience fig.2 Third day of experience fig.3 Fourth day of experience

Fig.4 The fifth day of the experiment Fig.5 The sixth day of the experiment

Light doesn't just show us the world, it changes it. Sunlight is a powerful substance that has a powerful effect on everything it interacts with.

The British chemist Joseph Priestley believed that light and life were one. He made the following experiment. The scientist placed the mouse in a hermetic glass cap and watched what happened to the air as a result of the mouse's breathing. Pretty soon, the mouse fell ill, reached complete exhaustion, and died. He believed that it was all about bad air, bad not only for animals, but also for plants. After that, Priestley placed the plant seedlings in a jar and left them for several weeks. To his surprise, they grew as if nothing had happened. It seemed that the bad air that killed the mouse only contributed to their prosperity. Then Priestley decided to plant another mouse in a jar of seedlings. The result was simply amazing. In a jar of plants, the animal suddenly revived. He called it luxurious air. What's more, the scientist found that the air quality not only improved with the seedlings growing in the jar, it literally jumped up if they were illuminated. This showed that illumination of green matter in plants could restore air and create conditions for the survival of animals for quite a long time.

Joseph Priestley proved that plants purify the air and make it breathable. Later it turned out that in order for the plant to purify the air, light is needed. All the oxygen that almost all living creatures of our planet breathe is released by plants in the process of photosynthesis. Priestley's experiments for the first time made it possible to explain why the air on Earth remains "clean" and can support life, despite the burning of countless fires and the breath of many living organisms. He said: "Thanks to these discoveries, we are confident that plants do not grow in vain, but purify and ennoble our atmosphere." And none of this would have been possible without sunlight.

Experiments and observations

Rays of light are straight.

A huge amount of data indicates that the beam of light is rectilinear. It is enough to at least remember the beam that breaks through the gap formed between the thick curtains. At this moment, we see a large number of direct golden rays. Also, the straightness of the rays may be evidenced by the fact that an object illuminated by the Sun gives clearly defined shadows. In fact, we judge the position of the objects around us in space, implying that the light from the object hits our eye along rectilinear trajectories. Our orientation in the outer world is entirely based on the assumption of a rectilinear propagation of light.

Based on the above, we will conclusion : light in a transparent homogeneous medium propagates in a straight line.

The rays are refracted.

Then I did another experiment. To do this, he took a cup, put it on the table and put a coin in it. I can see it perfectly, since the rays reflected by the coin hit my eye directly (Fig. 6). Then I sat down so that the coin was no longer visible (Fig. 7). Now the edge of the cup blocked the way for the rays, and I stopped seeing the coin. Then I slowly, so as not to budge the coin, began to pour water into the cup. At a certain moment, the coin became visible (Fig. 8). But how did this happen, because I and the coin remained in their place. Can doconclusion that the beam has changed its

Fig.6 trajectory when hit the water.

Fig.7 Fig.8

Take a glass beaker and pour water into it, then lower the pencil obliquely into it. It will seem to us that the pencil is broken, but in fact nothing happened to it (Fig. 9).So the beams really break?

Rice. 9

I'll give you another example. If you watch a person who has entered waist-deep water, it will seem that his legs have become shorter. It turns out that the fact is that the rays from the legs of a person standing in the water are refracted on the surface of the water. The eyes of the observer, on the other hand, perceive the rays as rectilinear, and therefore the feet appear to be located higher than in reality.

Based on the experiments and observations carried out, we will makeconclusion: a light beam that passes from one medium to another (from air to water, etc.), and falls at an angle to the interface, changes its direction at this boundary. This phenomenon is called refraction of light.

You can finally verify the refraction of rays using the following experiment: you need to put white paper on the table, put a comb with rare teeth on the edge of the table, cut a hole in the paper the size of a glass cup, insert a glass into it, and lift the paper a little, placing books under it. This is necessary so that the rays pass through the water, and not through the bottom of the glass. We will also place the lamp at the level of the table top, one and a half to two meters from the edge. After I turned on the lamp, long rays stretched across the paper, they are absolutely straight. But those that hit the glass broke. Behind a glass, they gathered in a bundle, and then fanned out (Fig. 11). Means,refraction of rays occurs in the glass. More precisely, where the rays enter it, and where they exit. But why did the rays, having passed through a convex round glass, gathered at one point? In this case, the glass performs the function of a lentil or lens, sinceLenses collect the rays of the sun at one point.

Fig.10 Fig.11

This can be verified by experiment. I decided to try to get fire from the ice floe. To do this, I took a large bowl, poured water into it and put it in the freezer. When the water froze, I took the bowl out of the refrigerator, lowered it into a basin of hot water so that the ice near the walls thawed. After that, I went out into the yard and laid out my "ice lighter" on a clean surface. Then I took it by the edges and, turning it towards the sun, collected its rays on a piece of dry paper. Unfortunately, I did not manage to set fire to the paper, apparently because such an experience is obtained only on a clear frosty day, when the sun's rays are very bright. But one thing I knew for suremy "ice lighter" refracted the sun's rays and gathered them into a beam.

Where does snow melt faster?

When I was little, I always wondered why snow melts faster where there are already thawed patches and black earth is visible. To do this, I decided to conduct the following experiment. I took two pieces of fabric of the same size, white and black. Then I laid them on the snow so that bright sunlight fell on them (Fig. 12). After two hours, I saw that the black patch had sunk into the snow, while the light one remained at the same level (Fig. 13,14).This means that under the black patch the snow melts faster, since the dark fabric absorbs most of the sun's rays falling on it. Light fabric, on the contrary, reflects most of the rays, so it heats up less than black.

fig.12

Fig.13 Fig.14

I read in a book about how these properties can be applied. In 1903, the ship of the German south polar expedition was frozen in the ice, and all the usual methods of liberation did not lead to any results. Explosives and the saws put into action removed only a few hundred cubic meters of ice and did not free the ship. Then they turned to the help of the sun's rays: from dark ash and coal they arranged a strip on the ice 2 km long and ten meters wide; it led from the ship to the nearest wide gap in the ice. It was the clear long days of a polar summer, and the sun's rays did what dynamite and saw could not do. The ice, having melted, broke along the piled strip, and the ship was freed from ice.

independent beams

When I went to the circus, I saw a very beautiful laser show there, where many multi-colored light rays are reflected on the surface of the tent in the form of intricate patterns or images of animals. I noticed that the rays intersect with each other, but this fact does not lead to image distortion. In other words, if one ray intersects with another ray at a certain point, then it does not change its direction and is not distorted, but continues to propagate in a straight line even after the intersection point.

We all watched the picture when the spotlights illuminate this or that site at night. Figure 15 clearly shows that the rays of light propagate in a straight line and do not lose this property even when crossing each other. That is, it can be assumed that light beams, when crossing, as a rule, do not perturb each other, that is, the light rays propagate independently of each other.

I decided to experiment and test my assumption. To do this, I needed two powerful flashlights. At night, when the lanterns were no longer on, we went outside and turned on the lanterns. Beams of light propagated in a straight line. After that, we directed the light rays in such a way that they intersect with each other (Fig. 16). Each of the light beams propagated in a straight line, independently of the other.

It can be concluded that the propagation of light rays is independent. This means that the action of one beam does not depend on the presence of other beams.

Fig.15

Fig.16

What color is sunlight?

Watching over sunlight, it seems to us that it is white. But is it really so? I tried two experiments.

First, I took a sheet of white cardboard, cut out a circle from it, divided it into eight identical sectors and painted the sectors in the colors of the rainbow (each sector in its own color), left the eighth sector white (Fig. 17). With the help of a drill, I quickly spun this circle. At this moment, it became white (Fig. 18).

Fig.17 Fig.18

For the next experiment, I needed a large sheet of cardboard that covered the entire window. In it, I cut a slot 2 cm wide and 10 cm high. Then I attached the cardboard to the window frame. The rays of the sun pass through the gap with a wide ribbon (Fig. 19). I placed the aquarium in such a way that the sun's rays passed through its two adjacent walls (Fig. 20). I poured water into the aquarium. In the place where the rays fell, I hung a sheet of white paper. This sheet turned out to be a wonderful colored ribbon. The order of colors on it turned out to be the same as in the rainbow (Fig. 21).

Fig.19 Fig.20

fig.21

In one experience I got White color the addition of multi-colored sectors, and in the other - all the colors of the rainbow turned out from white. But since all this is so, then the white color is not white at all. Or rather, it is not simple, but composite.

The sun sends us light in which all the rays are mixed: red, green, and violet ... This light seems white to us. But then he fell on a piece of paper and on a piece of wood. Why is one leaf white and the other green? Because paper reflects all the rays, and the same mixture of all colors gets into our eyes. And the greenery of plants best reflects the green rays. The rest are absorbed. This can be understood if you look through the red glass at the grass and trees. They appear very dark, almost black. This means that very few red rays are really reflected from them.

colored shadows

I noticed that if you light a table lamp in the room in the evening when you are doing your homework, then the shadow from the objects cast on the white sheets of the notebook has a gray color. I wondered what color the shadow would be if you screwed not an ordinary light bulb into a table lamp, but a colored one? For this experiment, I needed red and blue light bulbs.

First, I screwed a red bulb into the socket of a table lamp, put a sheet of white paper on the table. After that, I placed a small box between the lamp and the leaf. Her shadow appeared on the sheet of paper, but it was unexpected in color - not black or gray - but green. Having repeated this experiment, but with a blue light bulb, it turned out that the shadow became orange color(Fig.22, 23, 24).

Rice. 22

Rice. 23 Fig. 24

It turns out that these colors are complementary. So called colors that complement each other to white.

In order to understand which colors are complementary to each other, I decided to conduct the following experiment. I cut out red, orange, yellow, green, blue and purple squares 2x2 cm in size from colored paper. I put one of the colored squares in front of me on a sheet of white paper and looked at it for about thirty seconds, without straining my eyes, but at one point so that the image the square did not move across the retina. After that, I shifted my gaze to the white field, and a second later I saw a clear image of a square in additional color on the paper. So during the experiment, I learned that green is complementary to red, orange to blue, and purple to yellow. Each pair of complementary colors in the mixture should produce an achromatic white or gray color.

invisible light

The possibility of decomposing sunlight into a continuous sequence of rays of different colors was first experimentally shown by I. Newton in 1666. Directing a narrow beam of light at a trihedral prism, which penetrated into a darkened room through a small hole in the window shutter, he received on the opposite wall an image of a colored strip with iridescent alternation of colors, which he called the Latin word spectrum. Conducting experiments with prisms, Newton came to the following important conclusions: 1) ordinary "white" light is a mixture of rays, each of which has its own color; 2) rays of different colors, refracted in a prism, are deflected at different angles, as a result of which “white” light is decomposed into colored components.

But the physics of our time apart from visible to the eye rays discovered in nature many invisible. The sun sends invisible optical rays to Earth - ultraviolet, infrared - more than visible ones. Any body emits completely invisible infrared rays from the side. “Even a piece of ice is a source of light, but invisible light,” wrote Academician S.I. Vavilov.

In order to make sure that all bodies emit infrared radiation, I needed an infrared thermometer (Fig. 25).

Rice. 25

An infrared thermometer senses the energy of objects that contain radiated infrared energy. Its lens, aimed at an object, collects and focuses energy on an infrared sensor, which in turn generates a signal for the thermometer's microprocessor. This signal processed and displayed as degrees.

To verify the existence of invisible rays, I conducted several experiments.

For the first experience, I needed a regular electric stove. Such a stove warms everything around, including the surrounding air, mainly with infrared invisible radiation. For a correct experience, it is necessary to separate the invisible radiation of the tile from the flow of heated air. To do this, you can stretch a thin plastic film over the tile, which transmits infrared rays well, but does not allow hot air to pass through.

First, I measured the temperature of the turned off stove with an infrared thermometer, it turned out that it was 23 O C (Fig. 26). After that, I turned on one of the tiles and a minute later measured the temperature again, after stretching a plastic film over the tile. The device showed 264 About C (Fig. 27).

Rice. 26 Fig. 27

In the next experiment, I decided to repeat the experiment of the famous astronomer William Herschel. He directed a beam of light to a triangular prism and received a spectrum on the table. Herschel put well-calibrated thermometers in some parts of the spectrum. The thermometers warmed up and showed slightly different temperatures. But the thermometer, lying next to the red stripe of light, warmed up more than others - in the dark. In this way it was proved that there are invisible rays in solar radiation, which are refracted much worse than red rays, and these rays carry with them a noticeable, weighty part of the energy of the Sun.

For the next experiment, I needed a flashlight, a triangular glass prism, a sheet of white paper, and an infrared thermometer. By directing a beam of light from a flashlight onto a triangular prism, I obtained a spectrum (Fig. 28, 29). To better see it, I put a sheet of white paper on the place where it formed. Then, using an infrared thermometer, I measured the temperature approximately in the center of the spectrum and outside it near the red color. It turned out that the temperature is different: At the center of the spectrum, it was 25.2 O C, and outside the red color of the spectrum, i.e. in the zone of infrared radiation, - 25.7 Oh S.

Rice. 28 Fig. 29

In the next experiment, I decided to measure the infrared radiation emitted from the human body. To do this, my mother measured my body temperature with an infrared thermometer when I was at rest and after active physical activity. The thermometer showed the following temperature: 36 O C - when I was in a calm state (Fig. 30) and 33 O C - after exercise (Fig. 31).

Rice. 30 Fig. 31

It turns out that any cell on the surface of our body emits invisible infrared rays. And the faster we move, the more invisible rays are emitted from the surface, helping the skin to cool and keep the body temperature within reasonable, comfortable limits for the body.

conclusions

As a result of the study, I became convinced that sunlight and life are a single whole.

Thanks to the experiments carried out, I learned that the rays of light are rectilinear, that they are refracted.

I found out why snow melts faster where there are thawed patches.

I was convinced that the Sun sends us light, in which the rays of all the colors of the rainbow are mixed.

Empirically established that the shadow has a color and proved the presence of invisible light.

Based on the analysis of works of art, he formulated the image of the Sun.

It was very interesting for me to conduct research, I will definitely

I will continue to work in order to learn more about the sun's rays.

List of used literature.

Bludov M.I. Conversations on physics. – M.: Enlightenment, 1985.

Big Illustrated Encyclopedia / Per. from English. Yu.L. Amchenkova.- M.: CJSC "ROSMEN-PRESS", 2009.

The Great Illustrated Encyclopedia of the Schoolchild / Per. from English. E. Peremyshleva, V. Gibadullina, M. Krasnova, A. Filonova.- M.: Makhaon, 2008.

Brooks F., Chandler F., Clark F. et al. New Children's Encyclopedia / Per. from English. S.V. Morozova, N.S. Lyapkova, V.V. Plesheva and others - M.: CJSC "ROSMEN-PRESS", 2007.

Galpershtein L. Funny Physics. - M .: "Children's Literature", 1993.

Koltun M. World of Physics.- M .: "Children's Literature", 1987.

New encyclopedia of the student / Per. from English. O. Ivanova, T. Borodina. - M .: "Makhaon", 2010.

Experiments in the home laboratory. - M.: Science. Main edition of physical and mathematical literature, 1980.

Perelman Ya.I. Entertaining physics. - M .: Nauka publishing house, 1979.

Rabiza F.V. Simple experiments: Funny physics for children. - M .: "Children's Literature", 1997.

Feshchenko T., Vozhegova V. Physics. Schoolchildren's Handbook. - M .: Philological Society "Slovo", 1995.

Khilkevich S.S. Physics around us.-M: Science. Main edition of physical and mathematical literature, 1985.

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Sunlight plays a very difficult and vital role in wildlife! It can even be said that it is sunlight Live nature owes its existence. For plants and primitive microorganisms, the sun's rays regulate all life processes - the exchange of nutrients, growth and reproduction. For many small organisms, prolonged absence of sunlight means death. The human body is at such a stage of evolution that allows it to survive even in conditions of almost complete absence of sunlight, replacing it, for example, with candles and electrical lighting devices. But artificial lighting does not replace the work of sunlight on the synthesis of vitamin D, the production of serotonin, the regulation of the activity of the lysozyme enzyme, coenzymes, the activation of the complement system, etc. Of course, humanity also managed to get out in this case and came up with ultraviolet radiation lamps, but, as it turned out, that of the entire spectrum of energy sent to us by the Sun (infrared radiation, ultraviolet radiation, visible light), such "safe ultraviolet rays" turned out to be dangerous too. What is dangerous in solar ultraviolet, which, in general, is necessary for the human body for many metabolic processes?

It's all about the wavelength! But not the wave that occurs on the surface of a large reservoir, but electromagnetic wave moving photons. So scientists consider rays of light: in the form of a stream of photons. The ultraviolet flux is inhomogeneous. It includes:

• UV-A - ultraviolet-A, having a wavelength of 315-400 nm;
• UV-B - ultraviolet-B, having a wavelength of 280-315 nm;
• UV-C - ultraviolet-C, having a wavelength of 100-280 nm.

These varieties of ultraviolet radiation differ from each other in penetrating ability and biological activity in relation to living cells. UV-A has the highest degree of penetration, which is why it is dangerous for the body, since its biological effect is much wider and affects the structures of the body important for life support (macrophages, lymphocytes, blood vessels, collagen and elastane fibers, fibronectin, glucoaminoglycans). UV-A does not linger ozone layer, penetrates through glass, the stratum corneum of the skin, to a small extent is delayed by melanin.

UV-B is largely absorbed by the ozone layer, practically does not have the ability to penetrate glass, is almost completely retained by the stratum corneum and only 10 percent penetrates the dermis layer, but it is UV-B that can cause skin inflammation during sunburn and stimulate the production of melanin.

UV-C is absorbed by the ozone layer, but when artificial UV radiation is used, it is completely retained by the epidermis.

The all-penetrating flow of ultraviolet passes through the protective layers of the skin, reaches the cells of the body that are most vulnerable to it, and changes the structure of DNA, creating cellular mutations. At the dawn of the origin of life, this ability of sunlight, according to scientists, provided a variety of species of wildlife, but the human body, from the point of view of the cellular structure, is an established system that does not need to modify cells, for this reason, nature came up with a natural filter that delays the penetration ultraviolet to a great depth - a tan (or rather, a layer of pigment produced by skin cells - melanocytes).

But no matter what protective mechanisms nature invents for the body, a person manages to bypass them. In order for the mechanism of melanin formation to start, a minimal superficial sunburn of skin cells is required, which is regarded as a signal for the work of melanocytes and melanin synthesis. But protective creams have been invented that prevent burns (that is, they prevent the penetration of UV-B rays, but not UV-A rays).

According to the results of the latest developments of scientists, the tan layer (as well as the layer sunscreen) is now considered not as overpowering to UV-A rays as previously thought.

UV-A rays do not cause burns, do not provoke thickening of the epidermis during sunbathing, but they are responsible for photoaging and UV-carcinogenesis (they damage DNA chains), disrupt the functioning of lymphocytes, disrupt the antigen-recognizing abilities of Langerhans cells (migrating dendritic cells - participants in cellular immunity ).

The results of excessive exposure to the sun will not be long in coming and will appear in the form of:

• Solar erythema (skin burn) or solar allergy (photodermatosis),
• Inhibition of the work of immune system agents,
• Activation of certain viral infections (for example, herpes infection, human papillomavirus),
• An increase in the number of moles (nevi),
• Skin cancer (melanoma, basalioma, carcinoma) or precancerous skin conditions,
• Malignancy of inactive tumors (adenoma, myoma, fibroma, lipoma, osteoma, lymphoma, neurinoma and others) and as a result: breast cancer, endometrial cancer, ovarian cancer, prostate cancer, bowel cancer, etc.

Prevention of negative solar effects on the human body gives its positive results, but for this it is necessary to adhere to certain rules of behavior in the open sun.

1. To sunbathe properly and not get sunburn, it is necessary to prepare the skin in advance for exposure to ultraviolet radiation, before leaving on vacation, weak in intensity, short sunbathing is necessary, which will allow the formation of a melanin layer to begin in advance (20-30 minutes in the sun in the time interval from 8 am to 10 am when the UV-A rays are not strong enough).
2. You can actively sunbathe only until 10 am and after 4-5 pm.
3. You should not sunbathe immediately after swimming and with moistened skin, water drops will increase the intensity of UV radiation according to the principle of a lens, the same will be true of the snow left on the skin while relaxing in high mountain areas.
4. Categorically can't be in the sun when using photosensitizing drugs (for example: drugs prepared from medicinal plants containing furocoumarins, St. John's wort; sulfonamides, tetracyclines, and others), they increase the traumatic effect of sunlight by increasing the sensitivity of the skin.
5. SPF - creams will save you from a burn, but will not save you from the penetration of dangerous UV-A radiation, this must be borne in mind.
6. It is better to wear loose-fitting and light-colored clothes in the open sun.
7. People with fair skin tones are better do not sunbathe in general, but take short-term sunbathing early morning.
8. In the presence of inactive tumors, cysts, fibroids, active sun is categorically contraindicated: analyze the consequences for yourself and your family. In general, before traveling to warm countries, it does not hurt to conduct an ultrasound scan of some organs to make sure that there are no dangerous elements described above.
9. Moles and other formations on the skin must be covered with clothing.
10. Often skin cancer is located in the neck, ears, face, so wear hats in the open sun that shade these places.
11. Protect your eyes from strong sunlight. It can cause injury to the cornea and retina of the eye - a burn and provoke diseases such as cataracts, etc. Sunglasses must have a layer UV protection, which will be written on the glasses themselves. For people with gray, blue and blue eyes, sunglasses are an essential item and a guarantee of future eye health.

All rules apply to lovers of winter sports, because in high mountainous areas dangerous ultraviolet radiation much more active on the human body than on the coast of the ocean or the sea, and the sun's rays reflected by snow can cause irreparable damage to the visual apparatus.

Solar hardening is a stronger type of hardening compared to other methods due to the action of sunlight. Hardening should be carried out carefully, because if the baby is too long in the sun, the body may overheat and even suffer from central nervous system. Invisible ultraviolet rays contain the greatest activity and effect on the body.

There are direct and indirect sunlight. The first ones fall to the ground without obstacles, indirect or scattered ones penetrate through clouds, tree leaves, not dense artificial canopies, etc. Scattered rays have a weaker effect on the body. Daylight is reflected (these are those that are not concentrated in one place) and scattered sun rays.

Due to its strong effect on the body, sunbathing for children has a number of limitations:

• It is advisable to start hardening with sunbathing after mastering air baths.
• The smaller the baby, the greater the sensitivity to sunlight. Because of this, care must be taken when sunbathing.
• Sunbathing is recommended to take 1.5 hours after a meal, and finish half an hour before the next meal. This is necessary due to the fact that in hot weather conditions for digestion worsen.

An important condition of the procedures is gradualness, which can be achieved in several ways.:

• the best time for procedures in summer is morning from 8 to 11 o'clock, or after 16 o'clock, in autumn and spring from 10 to 14
• very good if it will be scattered rays due to cloudiness
• during the first procedures, it is advisable to wear clothing that suits the weather, but covers as much skin as possible, gradually increase the area of ​​​​exposure to the sun through clothing
• you can sunbathe in shady places

direct sunlight children under 1 year old are contraindicated, but this does not mean that the baby cannot be taken out into the sun, because this is a very good prevention of rickets. For such children, only reflected and scattered rays are used.

You need to start hardening in sunny, not windy weather. Wear a bodysuit or T-shirt with panties, and cover your head with a scarf. It is recommended to completely undress the children after 30 minutes of being outside at a temperature in the shade of at least 22-23˚. The duration of the procedure for the crumbs should begin with 2-3 minutes. bringing 5-6 minutes a day, increasing every two days a couple of minutes more. This is enough time for babies.

Children from 1-3 years old sunbathing should be taken carefully, at a temperature in the shade of 20-22˚. Bathing in direct sunlight should not exceed 15 minutes. in a day.

When choosing places for walking, keep in mind that the asphalt surface heats the air much more than the grassy one. Do not allow the child to overheat, and at the first signs (sweating, redness of the face), take the baby into the shade, let him drink, wash. To prevent the baby from overheating, support water balance, Be sure to offer your child a drink in the heat in the summer.

Under the influence of sunlight, the metabolism is accelerated, the excretion of metabolic products through the skin improves, immunity is stimulated. Vitamin D, which is very important, especially for babies, is produced.

Beware of sunburn, heatstroke and solar overheating!

Sunlight and its effects on the body- this question is of interest to many today, and, first of all, to those who are going to spend the summer with benefit, stock up on solar energy, get a beautiful and, most importantly, healthy tan.

What are the sun's rays and how do they affect our body?

The sun's rays are a stream of radiation represented by electromagnetic oscillations of different wavelengths.
The spectrum of rays emitted by the sun is wide and varied both in frequency and wavelength, and in its effect on a living organism.

There are several main areas of this spectrum:

1. Gamma radiation (invisible spectrum)

2. X-ray radiation (invisible spectrum) - with a wavelength<170 нм

3. Ultraviolet radiation (invisible spectrum) - with a wavelength of 170 to 350 nm

4. Actually sunlight (spectrum visible to the eye) - with a wavelength of 350 to 750nm

5. Infrared spectrum, (invisible, having a thermal effect) - with a wavelength> 750nm

The most active in terms of biological effects on a living organism is the sun's ultraviolet radiation.- they have a hormone-protective effect on the body, contribute to the formation of a "tan", stimulate the production of the "hormone of happiness" - serotonin and other biologically important components that increase the vitality and viability of a living organism.

In the ultraviolet spectrum, there are 3 groups of beams, characterized by various effects on a living organism:
UV rays A with a wavelength from 400 to 320 nm

These rays have the lowest level of radiation. The level of these rays in the solar spectrum remains constant throughout the day and year.
For them, there are practically no barriers. They have the lowest harmful effects on the body, however, their constant presence accelerates the processes of natural aging of the skin, since penetrating through the layers of the skin to the growth layer, they damage the base and structure of the skin, destroying collagen and elastin fibers.
In this regard, the elasticity of the skin deteriorates, which contributes to the appearance of wrinkles, the processes of premature aging are accelerated, the protective mechanisms of the skin are weakened, making it more susceptible to infections and, possibly, oncological diseases.
UV rays B with a wavelength from 320 to 280 nm

Rays of this type reach Earth's surface only at certain times of the year and hours of the day.
Depending on air temperature and geographic latitude, they usually enter the atmosphere between 10:00 and 16:00.
It is these rays that are involved in the activation of the synthesis of vitamin D3 in the body, which is the most important positive factor in their impact.
However, the same rays, when exposed to human skin for a long time, can change the genome of skin cells in such a way that they begin to multiply uncontrollably and form skin cancer.
UV rays C with a wavelength from 280 to 170 nm
This is the most dangerous part of the ultraviolet radiation spectrum, which unconditionally provokes the development of skin cancer.
But in nature, everything is arranged very wisely. Both harmful rays C and most of the rays B (90%) are absorbed by the ozone layer of the Earth, not reaching its surface. Thus, nature carefully protects all life on the planet from extinction.
Depending on the frequency, duration and intensity of exposure to ultraviolet radiation, our body develops:
positive effects- the formation of vitamin D, a balanced synthesis of melanin and the formation of a beautiful tan, the synthesis of serotonin, the most important regulator of the endocrine system, the synthesis of mediators that regulate the biorhythms of our body. That is why after the summer we feel a special surge of strength, increased vitality and good mood.
negative effects- skin burns, damage to collagen fibers, the appearance of cosmetic defects in the form of hyperpigmentation - chloasma and skin cancers (God forbid anyone!)

What happens in our skin when exposed to sunbeams?

The intake of vitamin D in our body is carried out in two ways:
due to its formation in the skin under the influence of ultraviolet rays B (endogenous pathway);
due to its entry into the body with food or biologically active additives (exogenous route);
The endogenous pathway for the formation of vitamin D3 is a rather complex process of biochemical reactions that occur without the participation of enzymes, but with the obligatory participation of ultraviolet irradiation (rays B).
With regular and sufficient solar exposure (insolation), the amount of vitamin D3 synthesized in the skin in the process of photochemical reactions fully provides the body's needs for this vitamin.
It is photochemical processes in the skin that ensure the work of the D-hormonal system in the body, and the activity of these processes is directly dependent on the intensity of exposure and the spectrum of ultraviolet radiation and inversely on the degree of pigmentation (or tanning) of the skin.
It has been proven that the more pronounced the tan, the more time it takes for the accumulation of provitamin D3 in the skin (instead of the usual 15 minutes - 3 hours).

And this is understandable from the point of view of physiology, since tanning is a protective mechanism of our skin and the melanin layer formed in it acts as a kind of barrier to both UVB rays, which are a mediator of photochemical processes, and class A UVA rays, which provide the thermal stage of the conversion of provitamin D3 to vitamin D3 in the skin.

But vitamin D, supplied with food, only compensates for its deficiency in case of insufficient production of it in the process of photochemical synthesis.

Why is this happening?

The place of synthesis of vitamin D3 is adipocytes - fat cells located in the subcutaneous fat, with 80% of it being synthesized in the epidermis and only 20% in the dermis.

The initial working substrate for vitamin synthesis is the hormone-like substance 7-dehydrocholesterol (provitamin D) contained in fat cells.
With age, the mass of the substrate decreases due to the natural aging of the skin, and this, of course, affects both the amount of synthesized vitamin and calcium metabolism in the body.

It has been proven that the concentration of provitamin D contained in the skin by the age of 80 is reduced by about 50% of the level of its content in 20 years.

That is why, with age, the risk of developing osteoporosis becomes much higher than in youth.
Thus, the more active the photochemical processes in the skin are, the more vitamin D3 is synthesized in the body.
But, vitamin D3 formed in this way in the skin (as well as vitamin D3 received with food) have a rather weak biological activity; in order to become an active hormone, it has yet to cling to a protein molecule (D-binding protein) and, in such a protein-bound state, first go to the liver, then to the kidneys, where its active metabolites will be synthesized from vitamin D3, including alcitriol 1,25(OH)2D3, the content of which in the blood determines the saturation of the body with vitamin D3

It is calcitriol that ensures the performance of a number of functions in the body, the main of which is the regulation of metabolism and mineralization of bone tissue.

I have already mentioned that the photochemical reactions of the formation of vitamin D3 in the skin occur in several stages and only when exposure of the skin to light and thermal energy with certain wavelengths.
First stage This process is due to the impact of UVB rays with a wavelength of 290-300 nm (the middle part of UVB rays) on the constantly present and inexhaustible source of provitamin D3 in the skin 7-dehydrocholesterol.
During this exposure, 7-dehydrocholesterol is converted to vitamin D3 (cholecalciferol), which is an unstable form of vitamin D3 and from which a wide variety of compounds can be formed with further exposure to light energy.
It can be either directly vitamin D3, or by-products of its synthesis, lumisterin and tachysterol, which are formed in the skin when exposed to UVB rays with a wavelength of more or less than 290 nm and are considered by science as regulatory factors that protect the body from hypervitaminosis D.

These by-products of vitamin D synthesis act on the body in different ways.

Tachysterol is a toxic and easily oxidized compound, it is formed in the skin when exposed to UV rays with a wavelength less than 290nm, at the same time, the shorter the wavelength (and this is the region of UVC rays), the more tachisterol and other by-products of overexposure are formed.
Lumisterin It is formed when exposed to UV - rays with a wavelength of more than 290 nm (UVA - rays), it does not have D-vitamin activity on its own, but helps to preserve the biological activity of vitamin D3.
Lumisterin in the skin is formed much more than tachysterol, which is due to the predominance of long-wave UVA rays in natural sunlight.

Second phase- this is final synthesis vitamin D3 in the skin.
Science has established that the completion of the synthesis of vitamin D3 occurs during the reaction thermal isomerization, proceeding at a skin temperature of about 37 ° and already without the participation of UVB rays.

Where does this thermal energy in the skin come from?

After all, the temperature in the basal layer of the epidermis, where these processes occur, is always significantly below the required level. It turns out that nature has created several heat sources for this reaction:
the warmth of the sunlight itself, which has a thermal effect, the greater the more length waves;
an increase in temperature in the skin, due to intense physical activity and, as a result, increased blood circulation, and hence metabolic processes in the skin;
hyperthermia of the skin, which accompanies the inflammatory erythema reaction in response to exposure to UVB rays.

It is clear that of all the heat sources listed above, when exposed to solar radiation, only erythema is always present, which means that it accompanies the process of photochemical synthesis of vitamin D3 in the skin in response to exposure to UVB radiation.

Thus, the process of formation of vitamin D3 in the skin seems to me the following picture:

UVB radiation, acting on provitamin D (7-dehydrocholesterol) contained in the skin, promotes the formation of vitamin D3, which does not have chemical resistance and biological activity.

At the same time, UVB radiation starts the process erythema inflammatory response in the superficial layers of the skin, which is absolutely necessary for the maturation of melanin in skin cells, their absorption by melanocytes and the formation of a natural photoprotective filter - sunburn.

It is clear that erythema, like any inflammatory reaction, is accompanied by an increase in metabolic processes that occur with the formation of heat, i.e. hyperemia.
hyperthermia, accompanying erythemal inflammatory response and is the very source of heat that is necessary to complete the reaction of the formation of vitamin D3 in the skin, namely, to convert the unstable form of vitamin D3 into its stable form, which is able to bind to the D-binding protein and undergo subsequent transformations in the liver and kidneys with the formation of active metabolites of vitamin D3.

By the way, the formed tanning melanin is a kind of regulator that protects the body from subsequent doses. UV radiation, from erythema and from excessive synthesis of vitamin D3.

At the same time, excessive irradiation in the absence of a formed tan and, depending on the skin phototype, can bring the erythema reaction beyond the boundaries of physiological norms and lead to acute manifestations of photoburn, and the resulting side compounds of vitamin D3 synthesis can lead to pronounced toxicological reactions.

Therefore, friends, before you wallow in the sun all day long with the thought of a beautiful tan, prioritize and think about what benefits such a tan will bring to you.

Today, science has already established that to fully meet the daily needs of the body with endogenous vitamin D3 for young and middle-aged people, a 10-20 minute stay in open sunlight containing UVB rays is enough.

Another thing is that these rays are not always present in the solar spectrum. It depends both on the geographical latitude and on the season of the year and
due to the fact that the Earth, rotating, changes the angle and thickness of the atmospheric layer through which the sun's rays pass.

This entails a change in the spectrum of rays reaching the Earth and, most often, reduces the presence of UVB rays in the spectrum, i.e. those that are directly involved in the synthesis of vitamin D.
In mid-latitudes, in the spring-summer period, the amount of UVB in the solar spectrum increases, and in the autumn-winter period it decreases until it disappears completely, which naturally affects the synthesis of vitamin D and the activity of the D-hormonal system.

By the way, a decrease in the level of UVB rays in the solar spectrum is an important pacemaker of the physiological activity of living organisms, and, according to scientists, it induces animals and birds to seasonal migrations, flights, hibernation, etc.

Thus, solar radiation is able to form vitamin D3 in the skin intermittently, but only at those moments when UVB rays are present in the spectrum of sunlight.
In Russia and neighboring countries, taking into account the geographical location, periods of solar radiation rich in UVB rays are distributed as follows:
practically all year round UVB rays are present in the spectrum of sunlight near the equator, but few of our compatriots can use them.
March to October(about 7 months) for residents of 40-43o north latitude (Sochi, Vladikavkaz, Makhachkala);
mid-March to mid-September(about 6 months) for residents near 45o north latitude (Krasnodar Territory, Crimea, Vladivostok);
April to September(about 5 months) for residents of 48-50o north latitude (Volgograd, Voronezh, Saratov, Irkutsk, Khabarovsk, Central regions of Ukraine);
mid-April to mid-August(about 4 months) - for residents of 55o north latitude (Moscow, Nizhny Novgorod, Kazan, Omsk, Novosibirsk, Yekaterinburg, Tomsk, Belarus, the Baltic countries);
May to July(about 3 months or less) for residents 60o and north (St. Petersburg, Arkhangelsk, Surgut, Syktyvkar, Scandinavian countries);
Add to this the number of cloudy days a year, the smoky atmosphere of large cities, and it becomes clear that the majority of the inhabitants of our Russia experience an unconditional deficiency of hormonotropic solar exposure.

This is probably why we intuitively strive for the sun, rush to the southern beaches, forgetting that the activity and spectral composition of solar radiation in the south is completely different, unusual for our body, and in addition to sunburn, it can provoke strong immune and hormonal surges that can increase risk of cancer and other diseases.

At the same time, the sun of the South is able to heal - how many childless couples have found the joy of motherhood and fatherhood after staying at its climatic resorts.

It's just that the golden mean and a reasonable approach should be observed in everything.
So, my friends, today we talked about sunshine and their impact on our body and once again understood that solar radiation plays a colossal role in our life.

Everything that happens on Earth is somehow connected with the Sun - ebb and flow, winter and summer, day and night, psycho-emotional changes in our mood, hormonal disruptions in the body - all this is the result of the influence of solar radiation.

Understanding and accepting the order of the flow of natural processes means making your life safer, longer and happier.

I sincerely wish you this, my dear readers!