UV is that part of the sun's radiation that gives the skin a nice brown tint and helps the body produce vitamin D, which is necessary for bones. This vitamin is also involved in the regulation of cell division and even to some extent prevents the development of colon and stomach cancer. Under the action of sunlight, the so-called “hormones of pleasure”, endorphins, are produced.

The human body is able to defend itself against harmful compounds produced under the influence of sunlight. DNA damage is quickly restored thanks to a special system that controls its integrity. And if, nevertheless, a change has occurred in the cell, it is recognized by the immune system as foreign and destroyed. Unfortunately, sometimes the body cannot cope with these damages, especially since UV suppresses the activity of the immune system. That is why, having arrived from warm countries, a person often catches a cold.

At the same time, suppression of the immune system is the main mechanism for treating diseases such as atopic dermatitis and some other skin diseases using ultraviolet radiation.

UV is divided into three spectra depending on the wavelength. Each spectrum has its own characteristics of impact on the human body.

• Spectrum C has a wavelength from 100 to 280 nm. This is the most active range, the rays easily penetrate the skin and cause a destructive effect on the cells of the body. Fortunately, such rays practically do not reach the Earth's surface, but are absorbed by the ozone layer of the atmosphere.
• Spectrum B (UVB) has a wavelength of 280-320 nm and makes up about 20% of all UV radiation that hits the Earth's surface. These rays give redness to the skin during sun exposure. They quickly cause the formation of active compounds in human skin, affecting DNA and causing a violation of its structure.
• Spectrum A, whose wavelength is 320-400 nm, accounts for almost 80% of the UV radiation that hits the human skin. Due to the longer wavelength, these rays have 1000 times less energy than UVB, so they almost do not cause sunburn. They are much less conducive to the production of biologically active substances that can affect DNA. However, these rays penetrate deeper than UVB, and the harmful substances they produce remain in the skin much longer.

Sunburn is primarily skin damage.

The damaging effect of the sun gradually accumulates in the body, and can manifest itself many years later in the form of skin cancer.

Parents, please note: if a child has a sunburn that causes blisters, especially if this happened more than once, the risk of developing melanoma in the future increases several times!

People are protected from the harmful effects of sunlight in different ways. Dark-skinned people have stronger protection, and people with red hair or blondes with blue eyes are more susceptible to the damaging effects of sunlight.

UV can sometimes contribute to the development of itchy rashes. In solar urticaria, itchy, nettle-like rashes develop between 30 minutes and two hours after exposure. Polymorphic light rash - in 1-2 days. This disease is also manifested by itchy rashes at the site of radiation, but they are slower than solar urticaria, and look different. There are other diseases for which UV is a stimulus to develop. For example, lupus erythematosus, rosacea, pellagra (lack of vitamin B3), and others.

Many medications taken by mouth can cause skin rashes when exposed to sunlight. There are some herbs that, after contact with the skin in the sun, cause severe redness and blistering. First of all, these are plants from the umbrella family, among which the strongest is hogweed. In addition, celery, parsley, lime, parsnips and others can cause such dermatitis.

How to protect yourself from the harmful effects of the sun, and at the same time benefit and enjoy it?

The answer is simple: you need to use sunscreen. It is not necessary to take a cream with maximum protection (SPF 50+). The product, which has SPF 15, already provides 80% protection from the sun's rays. This means that part of the UVB will reach the skin and have its positive effect. For sun protection creams to be effective, it is recommended to apply them 20 minutes before sunbathing, and reapply as recommended, usually every 2 hours. But be careful, the use of these drugs does not mean that you can stay under the sun indefinitely. It was this mistake that at one time led to a sharp increase in the incidence of melanoma - due to the lack of obvious sunburn due to protective cream, some sunbathed for too long.

Scientists have found that in order for the body to produce the amount of vitamin D it needs, it is enough to “show the sun” face and hands for 10-15 minutes a day.

Specialists of the EMC Clinic for Dermatovenereology and Allergology-Immunology will gladly give detailed recommendations on sun protection for you and your entire family.

Prominence on the surface

The radiation from the sun, which is known as sunlight, is a mixture of electromagnetic waves ranging from infrared (IR) to ultraviolet (UV) rays. It includes visible light, which lies between IR and UV in the electromagnetic spectrum.

Velocity of propagation of electromagnetic waves

All electromagnetic waves (EM) propagate at a speed of approximately 3.0x10*8 m/s in a vacuum. Space is not a perfect vacuum, it actually contains low concentrations of particles, electromagnetic waves, neutrinos and magnetic fields. Since the average distance between the Earth and the Sun is more than 149.6 million km, it takes about 8 minutes for the radiation to reach the Earth. The sun shines not only in the IR, visible and UV range. Basically, it emits high-energy gamma rays.

However, gamma-ray photons travel a long way to the surface, they are constantly absorbed by the solar plasma and re-emitted with a change in their frequency.

By the time they reach the surface, gamma ray photons are in the IR, visible, and UV spectra. Infrared radiation is the heat that we feel. Without it and visible light, life on Earth would be impossible. During solar flares, it also emits X-rays. When the Sun's electromagnetic radiation reaches the Earth's atmosphere, some of it is absorbed while the rest reaches the Earth's surface.

In particular, UV radiation is absorbed by the ozone layer and re-emitted as heat, which leads to heating of the stratosphere.

Man cannot live without sunlight. The sun gives us joy and helps us stay healthy. The sun's rays affect the production of serotonin, which improves mood and performance. They are necessary for the synthesis of vitamin D3, which is important for bones, without which calcium cannot be absorbed in the body.

Strictly speaking, what in our minds is considered the "sun", in fact, is just a small part of it. The human eye can only distinguish 40% of the sun's rays. The "invisible" Sun is infrared radiation (50%) and ultraviolet (10%).

Types of sunbeams:

1.Ultraviolet (UVC, UVB, UVA)
I) UVC - do not reach the Earth's surface, are completely absorbed by the upper atmosphere.
II) UVB - do not pass beyond the epidermis, cause a permanent tan.
III) UVA - penetrate the dermis, cause an "instant tan", which appears immediately after exposure to the sun and quickly disappears.

2. Infrared (IR-A, IR-B, IR-C) - thermal radiation of the Sun. IR-A rays are able to penetrate into the hypodermis, subcutaneous fat.

Do you remember the rhyme about "Every hunter wants to know where the pheasant sits"? Violet ("pheasant") is the last visible part of the solar spectrum, beyond which ultraviolet begins. Red ("every") is the first color of the solar spectrum available to our vision, preceded by invisible infrared rays.

Different types of sunlight differ from each other in an important physical characteristic - the wavelength, which determines their properties.

• UVB rays practically cannot penetrate normal glass. UVA and IR rays penetrate glass easily. Therefore, sitting by a closed window on a hot day is impossible to get a tan, but you can get a heat stroke.
• Infrared rays are unable to penetrate water. 60% of UVB and 85% of UVA rays penetrate to a sufficient depth. Therefore, being in a pond, we do not feel the heat, but we can get a sunburn.

Doctors do not recommend staying in the sun for a long time without using solar cosmetics. It is needed not only during a trip to the sea or excursions in the desert, but also when you just spend a lot of time outdoors: gardening, walking, skiing or cycling. Solar cosmetics will save you from troubles, the source of which can be the sun's rays.

UVB rays can cause burns and the appearance of age spots on the skin. UVA rays damage collagen and elastin fibers, causing the skin to lose firmness and elasticity.

Infrared A-rays have long been considered harmless. However, studies conducted at the University of Düsseldorf in 2003 showed that IRA rays, when exposed to human skin, lead to the formation of free radicals that destroy collagen fibers, leading to premature aging. Ladival was the first to use a patented formula with antioxidants to protect against the harmful effects of IRA rays in solar cosmetics. Its effectiveness has been clinically proven.

5 facts about the Sun:

1. The word "Sun" in English is an exception: it has the form of a personal pronoun and refers to the masculine gender - "He".

2. Lack of sunlight can cause a mental disorder - winter depression (Seasonal Affective Disorder). Its symptoms are drowsiness, lethargy, irritability, a feeling of hopelessness, anxiety.

3. The mass of the Sun is 99.85% of the mass of the solar system. The share of its other objects accounts for only 0.15%.

4. About 1 million planets, the size of the Earth, could fit inside the Sun.

5. The force of attraction on the Sun is 28 times greater than the force of attraction on the Earth: a person who is on Earth weighs 60 kilograms on the Sun would weigh 1680 kilograms.

The sun radiates its energy in all wavelengths, but in different ways. Approximately 44% of the radiation energy is in the visible part of the spectrum, and the maximum corresponds to the yellow-green color. About 48% of the energy lost by the Sun is carried away by infrared rays of the near and far range. Gamma rays, X-rays, ultraviolet and radio radiation account for only about 8%.

The visible part of solar radiation, when studied with the help of spectrum-analyzing instruments, turns out to be inhomogeneous - absorption lines are observed in the spectrum, first described by J. Fraunhofer in 1814. These lines arise when photons of certain wavelengths are absorbed by atoms of various chemical elements in the upper, relatively cold, layers of the Sun's atmosphere. Spectral analysis makes it possible to obtain information about the composition of the Sun, since a certain set of spectral lines characterizes a chemical element extremely accurately. So, for example, with the help of observations of the spectrum of the Sun, the discovery of helium was predicted, which was isolated on Earth later.

In the course of observations, scientists found that the Sun is a powerful source of radio emission. Radio waves penetrate into interplanetary space, which are emitted by the chromosphere (centimeter waves) and the corona (decimeter and meter waves). The radio emission of the Sun has two components - constant and variable (bursts, "noise storms"). During strong solar flares, the radio emission from the Sun increases thousands and even millions of times compared to the radio emission from the quiet Sun. This radio emission has a non-thermal nature.

X-rays come mainly from the upper layers of the chromosphere and the corona. The radiation is especially strong during the years of maximum solar activity.

The sun emits not only light, heat and all other types of electromagnetic radiation. It is also a source of a constant flow of particles - corpuscles. Neutrinos, electrons, protons, alpha particles, and heavier atomic nuclei all together make up the corpuscular radiation of the Sun. A significant part of this radiation is a more or less continuous outflow of plasma - the solar wind, which is a continuation of the outer layers of the solar atmosphere - the solar corona. Against the background of this constantly blowing plasma wind, individual regions on the Sun are sources of more directed, enhanced, so-called corpuscular flows. Most likely, they are associated with special regions of the solar corona - coronary holes, and also, possibly, with long-lived active regions on the Sun. Finally, the most powerful short-term particle fluxes, mainly electrons and protons, are associated with solar flares. As a result of the most powerful flashes, particles can acquire velocities that make up a significant fraction of the speed of light. Particles with such high energies are called solar cosmic rays.

Solar corpuscular radiation has a strong influence on the Earth, and above all on the upper layers of its atmosphere and magnetic field, causing many geophysical phenomena. The magnetosphere and the Earth's atmosphere protect us from the harmful effects of solar radiation.

What is the Sun? On the scale of the visible universe, this is just a tiny star on the outskirts of the galaxy, which is called the Milky Way. But for the planet Earth, the Sun is not just a hot bunch of gas, but a source of heat and light necessary for the existence of all life.

Since prehistoric times, the daylight has been an object of worship, its movement across the firmament has been associated with the manifestation of divine powers. Studies of the Sun and its radiation began even before the adoption of the heliocentric model of Nicolaus Copernicus, the greatest minds of ancient civilizations puzzled over his riddles.

Technological progress has given humanity the opportunity to study not only the processes inside and on the surface of the Sun, but also changes in the Earth's climate under its influence. Statistical data allow us to give a clear answer to the question of what solar radiation is, how it is measured and to determine its impact on living organisms that inhabit the planet.

What is called solar radiation

The nature of solar radiation remained unclear until, at the beginning of the 20th century, the eminent astronomer Arthur Eddington suggested that the source of the colossal solar energy is the thermonuclear fusion reactions that occur in its depths. The temperature near its core (about 15 million degrees) is sufficient for the protons to overcome the force of mutual repulsion and, as a result of the collision, form Helium nuclei.

Subsequently, scientists (in particular, Albert Einstein) discovered that the mass of the Helium nucleus is somewhat less than the total mass of the four protons from which it is formed. This phenomenon is called the mass defect. After tracing the relationship between mass and energy, scientists found that this excess is released in the form of gamma quanta.

When passing the path from the core to the surface of the Sun through the layers of its constituent gases, gamma quanta are crushed and turn into electromagnetic waves, among which is the light visible to the human eye. This process takes about 10 million years. And it takes only 8 minutes to reach the solar radiation of the earth's surface.

Solar radiation includes electromagnetic waves with a wide range and the solar wind, which is a stream of light particles and electrons.

What are the types of solar radiation and its characteristics

At the boundary of the Earth's atmosphere, the intensity of solar radiation is a constant value. The energy of the Sun is discrete and is transferred in portions (quanta) of energy, but their corpuscular contribution is relatively small, so the sun's rays are considered as electromagnetic waves that propagate evenly and rectilinearly.

The main wave characteristic is the wavelength, with which the types of radiation are distinguished:

• radio waves;
• infrared (thermal);
• visible (white) light;
• ultraviolet;
• gamma rays.

Solar radiation is represented by infrared (IR), visible (VS) and ultraviolet (UV) radiation in the ratio of 52%, 43% and 5%, respectively. The quantitative measure of solar radiation is considered to be energy illumination (energy flux density) - radiant energy arriving per unit of time per unit of surface.

Distribution of solar radiation over the earth's surface

Most of the radiation is absorbed by the earth's atmosphere and heats it up to the usual temperature for living organisms. The ozone layer transmits only 1% of ultraviolet rays and serves as a shield against more aggressive short-wave radiation.

The atmosphere absorbs about 20% of the sun's rays, scatters 30% in different directions. Thus, only half of the radiant energy, called direct solar radiation, reaches the earth's surface.

Several factors influence the intensity of direct solar radiation:

• the angle of incidence of the sun's rays (geographical latitude);
• distance from the point of impact to the Sun (season);
• the nature of the reflective surface;
• transparency of the atmosphere (cloudiness, pollution).

Scattered and direct radiation make up the total solar radiation, the intensity of which is measured in calories per unit surface. It is clear that solar radiation has an effect only in the daytime and is distributed unevenly over the earth's surface. Its intensity increases as it approaches the poles, however, snow reflects a large proportion of radiant energy, as a result of which the air does not heat up. Therefore, the total indicator decreases as you move away from the equator.

Solar activity shapes the Earth's climate and affects the life processes of the organisms that inhabit it. On the territory of the CIS countries (in the northern hemisphere), diffuse radiation prevails in the winter season, and direct radiation in the summer.

Infrared radiation and its role in the life of mankind

Solar radiation is represented predominantly invisible to the human eye. It is it that heats the earth's soil, which subsequently gives off heat to the atmosphere. Thus, the temperature and habitual climatic conditions are optimal for life on Earth.

In addition to the Sun, all heated bodies are sources of infrared radiation. All heating devices and devices that allow you to see more or less heated objects in conditions of poor visibility work according to this principle.

The fact that a person is not able to perceive infrared light does not reduce its effect on the body. This type of radiation has found application in medicine due to the following properties:

• expansion of blood vessels, normalization of blood flow;
• an increase in the number of leukocytes;
• treatment of chronic and acute inflammation of internal organs;
• prevention of skin diseases;
• removal of colloid scars, treatment of non-healing wounds.

Infrared thermographs allow timely detection of diseases that cannot be diagnosed using other methods (blood clots, cancerous tumors, etc.). Infrared radiation is a kind of "antidote" against negative ultraviolet radiation, therefore its healing properties are used to restore the health of people who have been in outer space for a long time.

The mechanism of action of infrared rays is not fully understood and, like any type of radiation, if used improperly, can be harmful to human health. Treatment with infrared rays is contraindicated in the presence of purulent inflammation, bleeding, malignant tumors, insufficiency of cerebral circulation and the cardiovascular system.

Spectral composition and properties of visible light

Light beams propagate in a straight line and do not overlap each other, which raises a fair question why the world around us strikes with a variety of different shades. The secret lies in the basic properties of light: reflection, refraction and absorption.

It is known for certain that objects do not emit light, it is partially absorbed by them and reflected at different angles depending on the frequency. Human vision has evolved over the centuries, but the retina of the eye can only perceive a limited range of reflected light in the narrow gap between infrared and ultraviolet radiation.

The study of the properties of light has given rise not only to a separate branch of physics, but also to a number of non-scientific theories and practices based on the effect of color on the mental and physical state of the individual. Using this knowledge, a person decorates the surrounding space in the most pleasing color for the eyes, which makes life as comfortable as possible.

Ultraviolet radiation and its effect on the human body

The ultraviolet spectrum of sunlight consists of long, medium and short waves, which differ in physical properties and the nature of the impact on living organisms. Ultraviolet rays, which belong to the long-wave spectrum, are mainly scattered in the atmosphere and do not reach the earth's surface. The shorter the wavelength, the deeper the ultraviolet penetrates into the skin.

Ultraviolet radiation is essential for sustaining life on Earth. UV rays have the following effects on the human body:

• saturation with vitamin D, necessary for the formation of bone tissue;
• prevention of osteochondrosis and rickets in children;
• normalization of metabolic processes and synthesis of beneficial enzymes;
• activation of tissue regeneration;
• improvement of blood circulation, expansion of blood vessels;
• increased immunity;
• removal of nervous excitement by stimulating the production of endorphins.

Despite the long list of positive qualities, sunbathing is not always effective. Prolonged exposure to the sun at unfavorable times or during periods of abnormally high solar activity nullifies the beneficial properties of UV rays.

Ultraviolet irradiation in high doses has the opposite result as expected:

• erythema (reddening of the skin) and sunburn;
• hyperemia, puffiness;
• increase in body temperature;
• headaches;
• dysfunction of the immune and central nervous systems;
• loss of appetite, nausea, vomiting.

These signs are symptoms of sunstroke, in which the deterioration of a person's condition can occur imperceptibly. Procedure for sunstroke:

• move the person from the area exposed to direct sunlight to a cool place;
• put on your back and raise your legs to an elevation to normalize blood circulation;
• rinse your face and neck with cool water, preferably make a compress on your forehead;
• provide the opportunity to breathe freely and get rid of tight clothing;
• for half an hour, give a drink of a small amount of clean cold water.

In severe cases, with loss of consciousness, it is necessary to call an ambulance team and, if possible, bring the victim to his senses. Medical assistance to the patient consists in the emergency administration of glucose or ascorbic acid intravenously.

Safe tanning rules

UV rays stimulate the synthesis of a special hormone melanin, with the help of which human skin darkens and takes on a bronze hue. Disputes about the benefits and harms of tanning have been going on for decades.

It has been proven that sunburn is a protective reaction of the body to ultraviolet radiation, and excessive sunbathing increases the risk of malignant tumors.

If the desire to pay tribute to fashion prevails, you need to understand what solar radiation is, how to protect yourself from it and follow simple recommendations:

• sunbathe gradually exclusively in the morning or evening;
• do not stay in direct sunlight for more than an hour;
• apply protective agents to the skin;
• drink more pure water to avoid dehydration;
• include in the diet foods that contain vitamin E, beta-carotene, tyrosine and selenium;
• limit the consumption of alcoholic beverages.

The reaction of the body to ultraviolet radiation is individual, so the time for sunbathing and their duration should be selected taking into account the type of skin and the state of human health.

Tanning is highly contraindicated for pregnant women, the elderly, people with skin diseases, heart failure, mental disorders and in the presence of malignant tumors.