Sun rays. Advantages and disadvantages. Why sun rays are good for health Types of sun rays

If you look at the Sun when it is partially obscured by clouds and hidden behind these clumps of atmospheric water, you may see a familiar sight: rays of light breaking through the clouds and falling to the ground. Sometimes they seem parallel, sometimes they seem to diverge. Can sometimes see the shape of the Sun through the clouds. Why is this happening? Our reader this week asks:

Can you explain to me why on a cloudy day you can see the sun's rays breaking through the clouds? It seems to me that since the Sun is much larger than the Earth, and since its photons reach us along roughly parallel paths, we should see the entire sky evenly illuminated, rather than seeing a small ball of light.

On a typical sunny day, the entire sky is lit up. The rays of the Sun fall almost parallel to the Earth because the Sun is very far away and it is very large compared to the Earth. The atmosphere is transparent enough for all sunlight to reach the Earth's surface or be scattered in all directions. The last effect is responsible for the fact that on a cloudy day something can be seen outside - the atmosphere perfectly scatters sunlight and fills the surrounding space with it.

This is why on a bright sunny day your shadow will be darker than the rest of the surface on which it falls, but will still remain illuminated. In your shadow, you can see the earth in the same way as if the Sun had disappeared behind the clouds, and then everything else becomes as dim as your shadow, but still illuminated by diffused light.

With this in mind, let us return to the phenomenon of solar rays. Why is it that when the Sun hides behind the clouds, you can sometimes see rays of light? And why do they sometimes look like parallel columns, and sometimes like diverging ones?

The first thing to understand is that the scattering of sunlight, when it collides with atmospheric particles and is redirected in all directions, always works - whether the Sun is hidden behind the clouds or not. Therefore, during the day there is always a basic level of lighting. That is why it is “day”, and therefore, to find darkness during the day, you need to go deeper into the cave.

What are rays? They come from gaps or thin sections of clouds (or trees or other opaque objects) that do not block sunlight. This direct light appears brighter than its surroundings, but is only noticeable if it contrasts with a dark, shadowy background! If this light is everywhere, there will be nothing remarkable about it, our eyes will adapt to it. But if a bright beam of light is lighter than its surroundings, your eyes notice this and tell you the difference.

What about the shape of the rays? You might think that clouds act like lenses or prisms, deflecting or refracting rays and causing them to diverge. But that's not true; Clouds absorb and re-emit light equally in all directions, which is why they are opaque. The ray effect only occurs where clouds do not absorb most of the light. When taking measurements, it turns out that these rays are actually parallel, which corresponds to a large distance to the Sun. If you observe rays directed neither towards you nor away from you, but perpendicular to your line of sight, this is exactly what you will find.

The reason why it seems to us that the rays “converge” towards the Sun is the same as why it seems to us that the rails or road surface converge at one point. These are parallel lines, one part of which is closer to you than the other. The sun is very far away, and the point from which the beam comes is further from you than the point of its contact with the Earth! It's not always obvious, but that's why the beams take on the shape of beams, which is clearly visible when you see how close you are to the end of the beam.

Therefore, we owe the presence of a ray to the perspective of the shadows surrounding it and the ability of our eyes to distinguish between the brightness of direct light and the relative darkness surrounding it. And the reason the rays appear to converge is due to perspective, and because the landing point of these actually parallel rays of light is closer to us than their starting point at the bottom of the clouds. That's the science behind sunrays, and that's why they look the way they do!

The peculiarities of the impact of direct sunlight on the body today are of interest to many, primarily those who want to spend the summer profitably, stock up on solar energy and acquire 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 wavelength and frequency, and in its effect on the human body.

Types of sun rays

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 greater than 750 nm).

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

Ultraviolet radiation

There are 3 classes of rays in the ultraviolet spectrum that affect the body differently:

1. A-rays (wavelength - 400-320 nanometers). They have the lowest level of radiation and remain constant in the solar spectrum throughout the day and year. There are almost no barriers for them. The harmful effects of sun 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 germ 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 a.m. to 4 p.m. These sun rays take part in activating the synthesis of vitamin D3 in the body, which is their main positive property. However, with prolonged exposure to the skin, they can change the genome of cells in such a way that they begin to multiply uncontrollably and form cancer.
3. C-rays (wavelength - 280-170 nm). This is the most dangerous part of the UV radiation spectrum, which unconditionally provokes the development of cancer. But in nature, everything is very wisely arranged, and the sun’s harmful C rays, like most (90 percent) of B rays, are absorbed by the ozone layer without reaching the Earth’s surface. This is how nature protects all living things from extinction.

Positive and negative influence

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

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

Vitamin D synthesis

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

The endogenous pathway is a rather complex process of reactions that occur without the participation of enzymes, but with the obligatory 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 body's needs.

Tanning 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 tanning (degree of pigmentation). It has been proven that the more pronounced the tan, the longer it takes for provitamin D3 to accumulate in the skin (instead of fifteen minutes to three hours).

From a physiological point of view, this is understandable, since tanning is a protective mechanism of our skin, and the layer of melanin 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 into vitamin D3.

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

Vitamin D formation during sun exposure

Today it has already been established by science that to meet the daily requirement for endogenous vitamin D3, it is enough to stay under open class UV rays of the sun 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 geographic latitude, since the Earth, when rotating, changes the thickness and angle of the atmospheric layer through which the sun's rays pass.

Therefore, solar radiation 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 the geographical location, class B rich UV rays are distributed unevenly during periods of solar radiation. For example, in Sochi, Makhachkala, Vladikavkaz they last about seven months (from March to October), and in Arkhangelsk, St. Petersburg, Syktyvkar they last about three (from May to July) or even less. Add to this the number of cloudy days a year and the smoky atmosphere in large cities, and it becomes clear that the majority of Russian residents lack hormonotropic solar exposure.

This is probably why intuitively we 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 can heal, you just have to follow a reasonable approach in everything.

The sun is the main source of energy on Earth. Without it, life would not exist. And although everything literally revolves around the Sun, we very rarely think about how our star works.

Structure of the Sun

To understand how the Sun works, you first need to understand its structure.

• Core.
• Radiative transfer zone.
• Convective zone.
• Atmosphere: photosphere, chromosphere, corona, solar wind.

The diameter of the solar core is 150-175,000 km, about 20-25% of the solar radius. The core temperature reaches 14 million degrees Kelvin. Thermonuclear reactions constantly occur inside, producing helium. It is in the core that as a result of this reaction energy is released, as well as heat. The rest of the Sun is heated by this energy, it passes through all the layers to the photosphere.

The radiative transfer zone is located above the core. Energy is transferred through the emission and absorption of photons.

Above the radiative transfer zone is the convective zone. Here, energy transfer is carried out not by re-radiation, but by matter transfer. At high speed, the cooler substance of the photosphere penetrates into the convective zone, and radiation from the radiative transfer zone rises to the surface - this is convection.

The photosphere is the visible surface of the Sun. Most visible radiation comes from this layer. Radiation from deeper layers no longer penetrates into the photosphere. The average temperature of the layer reaches 5778 K.

The chromosphere surrounds the photosphere and has a reddish tint. Emissions - spicules - constantly occur from the surface of the chromosphere.

The last outer shell of our star is the corona, consisting of energetic eruptions and prominences that form the solar wind, spreading to the farthest corners of the solar system. The average temperature of the corona is 1-2 million K, but there are areas with 20 million K.

The solar wind is a stream of ionized particles propagating to the boundaries of the heliosphere at a speed of about 400 km/s. Many phenomena on Earth are associated with the solar wind, such as the aurora and magnetic storms.

Solar radiation

The solar plasma has high electrical conductivity, which contributes to the emergence of electric currents and magnetic fields.

The sun is the strongest emitter of electromagnetic waves in the world, which gives us:

• ultra-violet rays;
• visible light - 44% of solar energy (mainly yellow-green spectrum);
• infrared rays - 48%;
• X-ray radiation;
• radiation.

Only 8% of the energy is devoted to ultraviolet, x-ray and radiation. Visible light is located between the rays of the infrared and ultraviolet spectrum.

The Sun is also a powerful source of radio waves of non-thermal nature. In addition to all kinds of electromagnetic rays, a constant stream of particles is emitted: electrons, protons, neutrinos, and so on.

All types of radiation exert their influence on the Earth. It is this influence that we feel.

Exposure to UV rays

Ultraviolet rays affect the Earth and all living things. Thanks to them, the ozone layer exists, since UV rays destroy oxygen, which is modified into ozone. The Earth's magnetic field in turn forms the ozone layer, which, paradoxically, weakens the strength of UV exposure.

Ultraviolet radiation affects living organisms and the environment in many ways:

• promotes the production of vitamin D;
• has antiseptic properties;
• causes tanning;
• enhances the work of hematopoietic organs;
• increases blood clotting;
• alkaline reserve increases;
• disinfects surfaces of objects and liquids;
• stimulates metabolic processes.

It is ultraviolet radiation that promotes self-purification of the atmosphere, eliminates smog, smoke and dust particles.

Depending on latitude, the strength of exposure to UV radiation varies greatly.

Exposure to infrared rays: why and how the Sun heats

All heat on Earth is infrared rays, which appear due to the thermonuclear fusion of hydrogen to form helium. This reaction is accompanied by a huge release of radiant energy. About 1000 watts per square meter reaches the ground. It is for this reason that IR radiation is often called thermal.

Surprisingly, the Earth acts as an infrared emitter. The planet, as well as clouds, absorb infrared rays and then re-radiate this energy back into the atmosphere. Substances such as water vapor, water droplets, methane, carbon dioxide, nitrogen, some fluorine and sulfur compounds emit infrared rays in all directions. It is due to this that the greenhouse effect occurs, which maintains the Earth's surface in a constantly heated state.

Infrared rays not only heat the surfaces of objects and living beings, but also have other effects:

• disinfect;
• improve metabolism;
• stimulate blood circulation;
• relieve pain;
• normalize water-salt balance;
• strengthen the immune system.

Why does the sun heat weakly in winter?

Since the Earth rotates around the Sun with a certain axis tilt, the poles are tilted at different times of the year. In the first half of the year, the North Pole is turned towards the Sun, in the second - the South Pole. Accordingly, the angle of exposure to solar energy changes, as well as the power.

Nature gives me a clear answer to this question twice a year: in summer and winter. This is how things are in temperate climates, subtropics and the subarctic zone, while all other latitudes live either in constant summer conditions or are accustomed to permafrost. To understand this injustice, it is necessary to look at the behavior of the Earth from space.

Reasons for the uneven distribution of solar energy over the Earth's surface

First of all, the reason is hidden in the shape of the globe. If our planet were truly flat, as the first “luminaries” of geography wanted, then every continent would be illuminated like the Equator, and summer would never leave the Earth.

The actual shape of the Earth resembles an ellipsoid, which already excludes the uniform distribution of light over the surface: at the Equator, light rays fall at a right angle, which ensures maximum heating, and beyond the Arctic Circle, a small part of the solar energy hits the Earth and is immediately reflected at an obtuse angle into space .

Balance is an indicator of the reflectivity of the earth's surface. So, equatorial and tropical soils absorb large amounts of solar energy at any time and successfully warm up. In northern latitudes, the balance indicator is very high: the sun's rays cannot heat the ground, which is covered by snow caps reflecting the light.

Why is there summer and winter in temperate latitudes?

It is absolutely normal for us to divide the seasons into winter and summer, but if we are guided by what I said above, then the temperate zone lives in conditions of constant spring. This would be so if it were not for one more surprise in the properties of the Earth.

The earth makes the following movements:

• revolves around the Sun;
• rotates around its axis;
• changes its angle of inclination throughout the year.

Thanks to the latter, we can observe the change of seasons in our country. To understand how this works, imagine the Earth as a potato that you decide to fry whole in a frying pan. To give a more or less uniform blush, you will have to constantly unroll it and press the edges.

Many of us love to spend time in the sun, some want to bask in the warm rays, and others are chasing a good tan. But is this beneficial for the body and how does it affect human health? Learn about the benefits and harms of sunlight.

The benefits of sun rays

If you approach this issue wisely, tanning will have a positive effect on your health. When exposed to sunlight, vitamin D is produced, which has a beneficial effect on bones and teeth and promotes the absorption of calcium.

Ultraviolet radiation has a beneficial effect on the human immune system. Experts have long proven that exposure to the sun slows down the growth of cancer cells. When exposed to sunlight, the body receives more oxygen, which improves the functioning of the heart muscle and improves blood pressure.

Sun lovers get sick much less often and cope better with stress. When exposed to sunlight, important processes in the body are activated, such as breathing, blood circulation, and metabolism.

Harm from sun rays

Spending a lot of time in direct sunlight increases your risk of skin cancer. Do not forget that prolonged exposure to the sun contributes to premature aging of the skin. To avoid such problems, use various oils and creams that will protect the skin from drying out.

We must not forget about burns; the desire to quickly and deeply tan can bring you a lot of inconvenience and harm your health. Be aware of the risk of heatstroke; do not forget that in strong sunshine, your head should be covered.

What is the best time to sunbathe?

If you come on vacation to a warm region and want to tan, remember for the first 3-4 days you should refrain from long sunbathing. This will only harm you and your skin, and instead of a bronze tan, you may return home with burns.

If we talk about time, we must not forget that in the period from 12:00 to 16:00 the sun is most active and can harm your body. You should sunbathe before noon, preferably before 11 o'clock. The most favorable time is considered to be from 16:00 to 19:00. During this period, the risk of getting burns is minimal. In addition, evening sun rays will not affect your vision.

How to protect yourself from sun exposure

Before sunbathing, you should take care of protection. Be sure to purchase a hat with a visor or wide brim to avoid blows and burns on your face.

Don't forget about sunscreen, which needs to be applied half an hour before going outside. During this time, the cream will be absorbed and a protective film will form. Apply the product every two hours.

Be mindful of your eyes and protect them with a large visor or dark glasses.

Be careful with your health, remember that in pursuit of a tan you can harm your skin. Enjoy the sun wisely. We wish you good luck and don't forget to press the buttons and

28.07.2015 09:30

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