Simple explanation

What is Heaven?

The sky is infinity. For any people, the sky is a symbol of purity, because it is believed that God himself lives there. People, turning to the sky, ask for rain, or vice versa for the sun. That is, the sky is not just air, the sky is a symbol of purity and purity.

Sky - it is just air, that ordinary air that we breathe every second, that which cannot be seen and touched, because it is transparent and weightless. But we breathe transparent air, why does it acquire such a blue color overhead? Air contains several elements, nitrogen, oxygen, carbon dioxide, water vapor, various dust particles that are constantly in motion.

Physically

In practice, as physicists say, the sky is just air colored by the sun's rays. Simply put, the sun shines on the Earth, but for this the sun's rays must pass through a huge layer of air that literally envelops the Earth. And since the sunbeam has many colors, or rather seven colors of the rainbow. For those who do not know, it is worth recalling that the seven colors of the rainbow are red, orange, yellow, green, light blue, blue, purple.

Moreover, each ray has all these colors, and it, passing through this layer of air, then it sprays various colors of the rainbow in all directions, but the blue color is scattered most of all, due to which the sky acquires a blue color. In a nutshell, the blue sky is the splashes that a ray painted in this color gives.

And on the moon

There is no atmosphere and therefore the sky on the moon is not blue but black. Astronauts who go into orbit see a black-black sky, on which planets and stars sparkle. Of course, the sky on the moon looks very beautiful, but still I would not like to see a constantly black sky overhead.

The sky changes color

The sky is not always blue, it tends to change color. Everyone, probably, noticed that sometimes it is whitish, sometimes bluish-black ... Why is that? For example, at night, when the sun does not send its rays, we see the sky not blue, the atmosphere seems to us transparent. And through the transparent air, a person can see the planets and stars. And in the afternoon, the blue color will again reliably hide the mysterious space from prying eyes.

Various hypotheses Why is the sky blue? (hypotheses of Goethe, Newton, scientists of the 18th century, Rayleigh)

So many hypotheses were put forward at different times to explain the color of the sky. Observing how the smoke against the background of a dark fireplace acquires a bluish color, Leonardo da Vinci wrote: “... lightness over darkness becomes blue, the more beautiful the more excellent the light and dark are.” Approximately the same point of view was held Goethe, who was not only a world famous poet, but also the greatest natural scientist of his time. However, this explanation of the color of the sky proved to be untenable, since, as it became apparent later, mixing black and white can only give gray tones, and not colors. The blue color of the smoke from the fireplace is due to a completely different process.

After the discovery of interference, in particular in thin films, Newtontried to apply interference to explain the color of the sky. To do this, he had to admit that the water droplets are in the form of thin-walled bubbles, like soap bubbles. But since the water droplets contained in the atmosphere are actually spheres, this hypothesis soon "burst" like a soap bubble.

Scientists of the 18th century Marriott, Booger, Euler thought that the blue color of the sky is due to the own color of the constituent parts of the air. This explanation even received some confirmation later, already in the 19th century, when it was established that liquid oxygen is blue, and liquid ozone is blue. The closest to the correct explanation of the color of the sky came O.B. Saussure. He believed that if the air were absolutely clean, the sky would be black, but the air contains impurities that reflect predominantly blue color (in particular, water vapor and water droplets). By the second half of the 19th century. accumulated a wealth of experimental material on the scattering of light in liquids and gases, in particular, one of the characteristics of the scattered light coming from the firmament was discovered - its polarization. Arago was the first to discover and explore it. This was in 1809. Later, Babinet, Brewster and other scientists were engaged in research into the polarization of the firmament. The question of the color of the sky attracted the attention of scientists so much that the experiments on the scattering of light in liquids and gases, which had a much broader significance, were carried out from the angle of view “laboratory reproduction of the blue color of the sky.” "Brücke or" On the blue color of the sky, the polarization of light by cloudy matter in general "Tyndall. The successes of these experiments directed the thoughts of scientists on the right path - to look for the cause of the blue color of the sky in the scattering of sunlight in the atmosphere.

The first to create a coherent, rigorous mathematical theory of molecular scattering of light in the atmosphere was the English scientist Rayleigh. He believed that the scattering of light occurs not on impurities, as his predecessors thought, but on the air molecules themselves. Rayleigh's first work on light scattering was published in 1871. In its final form, his theory of scattering, based on the electromagnetic nature of light, established by that time, was presented in the work "On light from the sky, its polarization and color", published in 1899 Rayleigh (his full name is John William Strutt, Lord Rayleigh III) is often called Rayleigh Scattering for his work in the field of light scattering, unlike his son, Lord Rayleigh IV. Rayleigh IV is called Rayleigh Atmospheric for his great contribution to the development of atmospheric physics. To explain the color of the sky, we will give only one of the conclusions of Rayleigh's theory, and we will refer to others several times when explaining various optical phenomena.This conclusion says: the brightness, or intensity, of the scattered light changes in inverse proportion to the fourth power of the wavelength of light falling on the scattering particle Thus, molecular scattering is extremely sensitive to the slightest change in the wavelength of light, for example, the wavelength violet optical rays (0.4 microns) is about half the wavelength of red (0.8 microns). Therefore, violet rays will be scattered 16 times more strongly than red ones, and with the same intensity of the incident rays, there will be 16 times more in the scattered light. All other colored rays of the visible spectrum (blue, cyan, green, yellow, orange) will be included in the scattered light in quantities inversely proportional to the fourth power of the wavelength of each of them. If now all colored scattered rays are mixed in this ratio, then the color of the mixture of scattered rays will be blue.

Direct sunlight (that is, light emanating directly from the solar disk), losing mainly blue and violet rays due to scattering, acquires a faint yellowish tint, which intensifies when the Sun descends to the horizon. Now the rays have to travel more and more way through the atmosphere. On a long path, the loss of short-wave, i.e., violet, blue, blue, rays becomes more and more noticeable, and in the direct light of the Sun or the Moon, mainly long-wave rays - red, orange, yellow - reach the Earth's surface. Therefore, the color of the Sun and Moon becomes first yellow, then orange and red. The red color of the sun and the blue color of the sky are two consequences of the same scattering process. In direct light, after it passes through the atmosphere, mainly long-wave rays (red Sun) remain, while short-wave rays (blue sky) fall into the scattered light. So Rayleigh's theory very clearly and convincingly explained the riddle of the blue sky and the red sun.

sky thermal molecular scattering

We are all accustomed to the fact that the color of the sky is a fickle characteristic. Fog, clouds, time of day - everything affects the color of the dome over your head. Its daily change does not occupy the minds of most adults, which cannot be said about children. They are constantly wondering why the sky is blue in terms of physics or what colors the sunset red. Let's try to understand these not the most simple questions.

Changeable

It is worth starting with an answer to the question of what, in fact, the sky is. In the ancient world, it was really seen as a dome covering the Earth. Today, however, hardly anyone knows that no matter how high the curious explorer ascends, he will not be able to reach this dome. The sky is not a thing, but rather a panorama that opens when viewed from the surface of the planet, a kind of appearance, woven from light. Moreover, if you observe from different points, it may look different. So, from the one rising above the clouds, a completely different view opens than from the ground at this time.

A clear sky is blue, but as soon as the clouds come in, it turns gray, leaden, or off-white. The night sky is black, sometimes you can see reddish areas on it. This is a reflection of the city's artificial lighting. The reason for all such changes is light and its interaction with air and particles of various substances in it.

Nature of color

In order to answer the question of why the sky is blue from the point of view of physics, you need to remember what color is. This is a wave of a certain length. The light coming from the Sun to the Earth is seen as white. It is known from Newton's experiments that it is a bundle of seven rays: red, orange, yellow, green, light blue, blue and violet. Colors differ in wavelength. The red-orange spectrum includes the most impressive waves in this parameter. parts of the spectrum are characterized by a short wavelength. The decomposition of light into a spectrum occurs when it collides with molecules of various substances, while part of the waves can be absorbed, and part - scattered.

Cause investigation

Many scientists have tried to explain why the sky is blue in terms of physics. All researchers sought to detect a phenomenon or process that scatters light in the planet's atmosphere in such a way that as a result, only blue reaches us. Water was also the first candidate for the role of such particles. It was believed that they absorb red light and transmit blue, and as a result, we see a blue sky. Subsequent calculations, however, showed that the amount of ozone, ice crystals and water vapor molecules in the atmosphere was not enough to give the sky a blue color.

The reason is pollution

At the next stage of research, John Tyndall suggested that dust plays the role of the desired particles. Blue light has the greatest resistance to scattering, and therefore is able to pass through all layers of dust and other suspended particles. Tyndall conducted an experiment that confirmed his assumption. He created a model of a smog in a laboratory and illuminated it with bright white light. The smog took on a blue tint. The scientist made an unambiguous conclusion from his research: the color of the sky is determined by dust particles, that is, if the air of the Earth was clean, then not blue, but white skies shone above the heads of people.

Lord's research

The final point on the question of why the sky is blue (from the point of view of physics) was put by the English scientist, Lord D. Rayleigh. He proved that it is not dust or smog that paints the space overhead in the shade we are used to. It's about the air itself. Gas molecules absorb the largest and primarily the longest wavelengths, equivalent to red. The blue dissipates. This is how the color of the sky we see in clear weather is explained today.

The attentive will notice that, following the logic of scientists, the dome over your head should be purple, since this color has the shortest wavelength in the visible range. However, this is not a mistake: the proportion of violet in the spectrum is much less than that of blue, and human eyes are more sensitive to the latter. In fact, the blue we see is the result of mixing blue with purple and some other colors.

Sunsets and clouds

Everyone knows that at different times of the day you can see different colors of the sky. Photos of the most beautiful sunsets over the sea or lake are a great illustration of this. All sorts of shades of red and yellow, combined with blue and dark blue, make such a spectacle unforgettable. And it is explained by the same scattering of light. The fact is that during dusk and dawn, the sun's rays have to overcome a much larger path through the atmosphere than during the height of the day. In this case, the light of the blue-green part of the spectrum is scattered in different directions and the clouds located at the horizon line become colored in shades of red.

When the sky is covered with clouds, the picture changes completely. unable to overcome the dense layer, and most of them simply do not reach the ground. The rays that have managed to pass through the clouds meet with water drops of rain and clouds, which again distort the light. As a result of all these transformations, white light reaches the earth, if the clouds are small in size, and gray, when the sky is covered by impressive clouds, which again absorb part of the rays.

Another heaven

I wonder what on other planets Solar system when viewed from the surface, you can see the sky, which is very different from the earth. On space objects, deprived of the atmosphere, the sun's rays freely reach the surface. As a result, the sky here is black, without any shade. Such a picture can be seen on the Moon, Mercury and Pluto.

The Martian sky has a red-orange hue. The reason for this lies in the dust with which the planet's atmosphere is saturated. It is painted in different shades of red and orange. When the Sun rises above the horizon, the Martian sky turns pinkish-red, while the portion of it directly surrounding the luminary's disk appears blue or even purple.

The sky above Saturn is the same color as on Earth. The aquamarine skies stretch over Uranus. The reason lies in the methane haze located in the upper planets.

Venus is hidden from the eyes of researchers by a dense layer of clouds. It does not allow the rays of the blue-green spectrum to reach the planet's surface, so the sky here is yellow-orange with a gray stripe along the horizon.

Exploring overhead space during the day reveals no less wonders than exploring the starry sky. Understanding the processes taking place in the clouds and behind them helps to comprehend the reason for things that are quite familiar to the average person, which, nevertheless, not everyone can explain right away.

The joy to see and understand
is the most beautiful gift of nature.
Albert Einstein

The Riddle of Heavenly Blue

Why the sky is blue?...

There is no such person who has not thought about it at least once in his life. Medieval thinkers have already tried to explain the origin of the color of the sky. Some of them suggested that blue is the true color of air or some of its constituent gases. Others thought that the real color of the sky is black - the way it looks at night. During the day, the black color of the sky is combined with white - the sun's rays, and it turns out ... blue.

Now, perhaps, you will not meet a person who, wanting to get blue paint, would mix black and white. And there was a time when the laws of color mixing were still unclear. They were installed only three hundred years ago by Newton.

Newton also became interested in the secret of heavenly blue. He began by rejecting all previous theories.

First, he argued, a mixture of white and black never forms blue. Secondly, blue is not at all the true color of air. If this were so, then the Sun and Moon at sunset would not appear red, as it really is, but blue. The peaks of the distant snowy mountains would look like this.

Imagine that the air is colored. Even if it is very weak. Then its thick layer would act like colored glass. And if you look through the painted glass, then all the objects appear the same color as this glass. Why do distant snowy peaks appear pink to us, and not at all blue?

In a dispute with his predecessors, the truth was on Newton's side. He proved that the air is not colored.

Still, he did not solve the riddle of the blue sky. He was confused by the rainbow, one of the most beautiful, poetic phenomena of nature. Why does it suddenly appear and just as suddenly disappear? Newton could not be satisfied with the prevailing superstition: a rainbow is a sign from above, it portends good weather. He strove to find the material cause of every phenomenon. He also found the cause of the rainbow.

A rainbow is the result of light refraction in raindrops. Realizing this, Newton was able to calculate the shape of the rainbow arc and explain the sequence of colors in the rainbow. His theory could not explain only the appearance of a double rainbow, but it was possible to do this only three centuries later with the help of a very complex theory.

The success of the rainbow theory hypnotized Newton. He mistakenly assumed that the blue color of the sky and the rainbow were caused by the same cause. A rainbow does flare up when the sun's rays break through a swarm of raindrops. But the blue sky is visible not only in the rain! On the contrary, it is in clear weather, when there is not even a hint of rain, that the sky is especially blue. How did the great scientist not notice this? Newton thought that the smallest water bubbles, which, according to his theory, form only the blue part of the rainbow, float in the air in any weather. But this was a delusion.

First solution

Almost 200 years passed, and another English scientist, Rayleigh, took up this issue, not afraid that the task was beyond the power of even the great Newton.

Rayleigh worked in optics. And people who have dedicated their lives to the study of light spend a lot of time in the dark. Extraneous light interferes with the finest experiments; therefore, the windows of the optical laboratory are almost always covered with black, impenetrable curtains.

Rayleigh spent hours in his gloomy laboratory alone with beams of light escaping from the instruments. In the path of the rays, they circled like living dust particles. They were brightly lit and therefore stood out against the dark background. The scientist, perhaps, for a long time in thought, followed their smooth movements, similar to how a person watches the play of sparks in a fireplace.

Was it not these specks of dust dancing in the rays of light that suggested Rayleigh a new idea about the origin of the color of the sky?

Even in ancient times it became known that light propagates in a straight line. This important discovery could have been made by a primitive man, observing how, breaking through the cracks of the hut, the sun's rays fall on the walls and floor.

But he was hardly bothered by the thought why he sees light rays, looking at them from the side. And here there is something to think about. After all, sunlight is a ray from the gap to the floor. The eye of the observer is located to the side and, nevertheless, sees this light.

We also see the light from a searchlight directed into the sky. This means that part of the light somehow deviates from the direct path and is sent to our eye.

What makes him go astray? It turns out that the very specks of dust with which the air is full. Rays scattered by a speck of dust enter our eye, which, encountering obstacles, turn off the road and spread in a straight line from the scattering speck of dust to our eye.

"Isn't it these specks of dust that color the sky blue?" Rayleigh once thought. He did the math, and the guess turned into confidence. He found an explanation for the blue sky, red dawns and blue haze! Of course, the smallest particles of dust, the size of which is less than the wavelength of light, scatter sunlight and the more, the shorter its wavelength, Rayleigh announced in 1871. And since the violet and blue rays in the visible solar spectrum have the shortest wavelength, they are scattered most strongly, giving the sky a blue color.

The Sun and snowy peaks obeyed this calculation by Rayleigh. They even confirmed the scientist's theory. At sunrise and sunset, when sunlight passes through the greatest thickness of the air, violet and blue rays, says Rayleigh's theory, are scattered most strongly. At the same time, they deviate from the direct path and do not fall into the eyes of the observer. The observer sees mainly red rays, which are scattered much weaker. Therefore, at sunrise and sunset, the sun appears to us red. For the same reason, the peaks of the distant snowy mountains also appear pink.

Looking at the clear sky, we see blue-blue rays deviating from the straight path due to scattering and falling into our eyes. And the haze that we sometimes see near the horizon also seems to us blue.

An annoying trifle

Nice explanation, isn't it? He was so carried away by Rayleigh himself, scientists were so amazed at the harmony of the theory and Rayleigh's victory over Newton that none of them noticed one simple thing. And this trifle, nevertheless, should have completely changed their assessment.

Who would deny that far from the city, where there is much less dust in the air, the blue sky is especially clear and bright? It was hard to deny this to Rayleigh himself. So ... don't the dust particles scatter the light? What then?

He again revised all his calculations and made sure that his equations are correct, but this means that the scattering particles are really not dust particles. In addition, the dust particles that are present in the air are much larger than the wavelength of light, and calculations convinced Rayleigh that a large accumulation of them does not increase the blueness of the sky, but, on the contrary, weakens it. Light scattering by large particles weakly depends on the wavelength and therefore does not cause a change in its color.

When light is scattered by large particles, both the scattered and transmitted light remains white, therefore, the appearance of large particles in the air imparts a whitish color to the sky, and the accumulation of a large number of large droplets causes the white color of clouds and fog. It is easy to check this on a regular cigarette. The smoke coming out of it from the side of the mouthpiece always seems whitish, and the smoke rising from its burning end has a bluish color.

The smallest particles of smoke rising above the burning end of a cigarette are smaller than the wavelength of light, and in accordance with Rayleigh's theory, they scatter primarily violet and blue. But when passing through narrow channels in the thickness of the tobacco, the smoke particles stick together (coagulate), combining into larger lumps. Many of them become larger than the wavelengths of light, and they scatter all waves of light in about the same way. That is why the smoke coming from the side of the mouthpiece appears whitish.

Yes, it was useless to argue and defend the theory based on dust particles.

So, the mystery of the blue color of the sky again appeared before the scientists. But Rayleigh didn't give up. If the blue color of the sky is the purer and brighter, the cleaner the atmosphere, he reasoned, then the color of the sky cannot be caused by anything other than the molecules of the air itself. Air molecules, he wrote in his new articles, are the smallest particles that scatter the light of the sun!

Rayleigh was very careful this time. Before communicating his new idea, he decided to test it, somehow check the theory with experience.

The case presented itself in 1906. Rayleigh was helped by the American astrophysicist Abbot, who studied the blue glow of the sky at the Mount Wilson Observatory. By processing the results of measuring the brightness of the glow of the sky based on Rayleigh's scattering theory, Abbot calculated the number of molecules contained in each cubic centimeter of air. It turned out to be a huge number! Suffice it to say that if you distribute these molecules to all people inhabiting the globe, then each will get more than 10 billion of these molecules. In short, Abbot discovered that there are 27 billion times a billion molecules in every cubic centimeter of air at normal temperature and atmospheric pressure.

The number of molecules in a cubic centimeter of gas can be determined in different ways based on completely different and independent phenomena. All of them lead to closely coinciding results and give a number called the Loschmidt number.

This number is well known to scientists, and more than once it served as a measure and control in explaining the phenomena that occur in gases.

And now the number obtained by Abbott when measuring the glow of the sky coincided with great accuracy with the number of Loschmidt. But he used Rayleigh's scattering theory in his calculations. Thus, this clearly proved that the theory is correct, molecular light scattering really exists.

It seemed that Rayleigh's theory was reliably confirmed by experiment; all scholars considered her to be perfect.

She became generally recognized and entered all optics textbooks. One could breathe calmly: an explanation of the phenomenon has finally been found - so familiar and at the same time mysterious.

It is all the more surprising that in 1907, on the pages of a well-known scientific journal, the question was again raised: why is the sky blue ?!

Dispute

Who dared to question the generally accepted Rayleigh theory?

Ironically, this was one of Rayleigh's ardent fans and admirers. Perhaps no one appreciated and understood Rayleigh so well, did not know his work so well, was not interested in his scientific work as much as the young Russian physicist Leonid Mandelstam.

- In the nature of Leonid Isaakovich's mind, - later recalled another Soviet scientist, academician N.D. Papaleksi - had a lot in common with Rayleigh. And it is no coincidence that the paths of their scientific creativity often went in parallel and repeatedly crossed.

They crossed themselves this time too, on the question of the origin of the color of the sky. Prior to that, Mandelstam was mainly fond of radio engineering. For the beginning of our century, this was a completely new field of science, and few people understood it. After A.S. Popov (in 1895) only a few years passed, and there was a lot of work here. In a short period of time, Mandelstam carried out a lot of serious research in the field of electromagnetic oscillations as applied to radio engineering devices. In 1902 he defended his dissertation and at twenty-three received his Ph.D. in natural philosophy from the University of Strasbourg.

Dealing with the excitation of radio waves, Mandelstam, naturally, studied the works of Rayleigh, who was a recognized authority in the study of oscillatory processes. And the young doctor inevitably got acquainted with the problem of the color of the sky.

But, having become acquainted with the issue of the color of the sky, Mandelstam not only showed the fallacy, or, as he himself said, the "insufficiency" of the generally accepted theory of molecular scattering of light by Rayleigh, not only revealed the secret of the blue color of the sky, but also initiated studies that led to one of the most important discoveries of physics of the XX century.

It all began with a correspondence dispute with one of the greatest physicists, the father of quantum theory, M. Planck. When Mandelstam became acquainted with Rayleigh's theory, she captured him with her reticence and internal paradoxes, which, to the surprise of the young physicist, the old, experienced Rayleigh did not notice. The inadequacy of Rayleigh's theory was especially clearly revealed in the analysis of another theory based on it by Planck to explain the attenuation of light when it passes through an optically homogeneous transparent medium.

In this theory, it was taken as a basis that the very molecules of the substance through which light passes are sources of secondary waves. To create these secondary waves, Planck argued, part of the energy of the passing wave is spent, which is then weakened. We see that this theory is based on the Rayleigh theory of molecular scattering and is based on its authority.

The easiest way to understand the essence of the matter is by examining the waves on the surface of the water. If a wave meets fixed or floating objects (piles, logs, boats, etc.), then small waves scatter from these objects in all directions. This is nothing more than scattering. Part of the incident wave energy is spent on the excitation of secondary waves, which are quite analogous to scattered light in optics. In this case, the initial wave is weakened - it fades out.

Floating objects can be much shorter than the wavelength of the water traveling. Even small grains will cause secondary waves. Of course, as the size of the particles decreases, the secondary waves generated by them weaken, but they will still take up the energy of the main wave.

This is approximately how Planck imagined the process of weakening a light wave when it passes through a gas, but the role of grains in his theory was played by gas molecules.

Mandelstam became interested in this work.

Mandelstam's train of thought can also be explained using the example of waves on the surface of the water. You just need to consider it more closely. So, even small grains floating on the surface of the water are sources of secondary waves. But what happens if these grains are poured so densely that they cover the entire surface of the water? Then it turns out that individual secondary waves caused by numerous grains will fold in such a way that they completely extinguish those parts of the waves that run to the sides and back, and the scattering will stop. There will be only a wave running forward. She will run forward, not weakening at all. The only result of the presence of the entire mass of grains will be a slight decrease in the speed of propagation of the primary wave. It is especially important that all this does not depend on whether the grains are stationary or whether they move along the surface of the water. The aggregate of grains will simply act as a load on the surface of the water, changing the density of its upper layer.

Mandelstam performed a mathematical calculation for the case when the number of molecules in the air is so large that even in such a small area as the length of a light wave, a very large number of molecules are contained. It turned out that in this case the secondary light waves, excited by individual chaotically moving molecules, add up in the same way as waves in the example with grains. This means that in this case the light wave propagates without scattering and attenuation, but at a slightly lower speed. This refuted the theory of Rayleigh, who believed that the motion of scattering particles in all cases ensures the scattering of waves, which means that it also refuted the Planck theory based on it.

So sand was discovered under the foundation of the scattering theory. The entire stately building shook and threatened to collapse.

Coincidence

But what about the determination of the Loschmidt number from measurements of the blue glow of the sky? After all, experience confirmed the Rayleigh theory of scattering!

"This coincidence should be regarded as accidental," wrote Mandelstam in 1907 in his work "On optically homogeneous and turbid media."

Mandelstam showed that the disordered movement of molecules cannot make a gas homogeneous. On the contrary, in a real gas there are always the smallest rarefaction and condensation resulting from chaotic thermal motion. It is they who lead to the scattering of light, since they violate the optical uniformity of the air. In the same work, Mandelstam wrote:

"If the medium is optically inhomogeneous, then, generally speaking, the incident light will be scattered to the sides."

But since the dimensions of the inhomogeneities resulting from chaotic motion are less than the length of light waves, the waves corresponding to the violet and blue parts of the spectrum will be scattered mainly. And this leads, in particular, to the blue color of the sky.

So the riddle of heavenly blue was finally solved. The theoretical part was developed by Rayleigh. The physical nature of the scatterers was established by Mandelstam.

The great merit of Mandelstam is that he proved that the assumption of perfect homogeneity of the gas is incompatible with the fact that light is scattered in it. He realized that the blue color of the sky proves that the homogeneity of gases is only apparent. More precisely, gases appear homogeneous only when examined by coarse instruments, such as a barometer, balance or other instruments, which are simultaneously influenced by many billions of molecules. But the light beam senses incomparably smaller quantities of molecules, measured only in tens of thousands. And this is enough to establish beyond dispute that the density of the gas is continuously subject to small local variations. Therefore, a medium that is homogeneous from our "rough" point of view is in fact non-uniform. From the "point of view of light" it appears cloudy and therefore scatters light.

Random local changes in the properties of a substance resulting from the thermal motion of molecules are now called fluctuations. Having clarified the fluctuation origin of molecular scattering of light, Mandelstam paved the way for a new method of studying matter - the fluctuation, or statistical, method, which was later developed by Smolukhovsky, Lorentz, Einstein and himself into a new large department of physics - statistical physics.

The sky should be twinkling!

So, the secret of the blue sky was revealed. But the study of light scattering did not stop there. Paying attention to the almost imperceptible changes in the density of the air and explaining the color of the sky by fluctuation scattering of light, Mandelstam, with his heightened instinct of a scientist, discovered a new, even more subtle feature of this process.

After all, air inhomogeneities are caused by random fluctuations in its density. The magnitude of these random inhomogeneities, the density of clumps, changes over time. Therefore, the scientist reasoned, the intensity should also change over time - the strength of the scattered light! After all, the denser the clumps of molecules, the more intense the light scattered on them. And since these clots appear and disappear chaotically, the sky, simply speaking, should flicker! The strength of its glow and its color must change all the time (but very weakly)! But has anyone ever noticed such a flicker? Of course not.

This effect is so subtle that you cannot see it with the naked eye.

None of the scientists also observed such a change in the glow of the sky. Mandelstam himself did not have the opportunity to verify the conclusions of his theory. The organization of the most complex experiments was hampered at first by the meager conditions of tsarist Russia, and then by the difficulties of the first years of the revolution, foreign intervention and civil war.

In 1925, Mandelstam became the head of the department at Moscow University. Here he met with an outstanding scientist and skilled experimenter Grigory Samuilovich Landsberg. And so, bound by deep friendship and common scientific interests, together they continued the storming of secrets hidden in the weak rays of scattered light.

The optical laboratories of the university in those years were still very poor in instruments. There was not a single device at the university that could detect the flickering of the sky or those small differences in the frequencies of incident and scattered light that theory predicted are the result of this flicker.

However, this did not stop the researchers. They gave up the idea of \u200b\u200bimitating the sky in the laboratory. It would only complicate an already subtle experience. They decided to study not the scattering of white - complex light, but the scattering of rays of one, strictly defined frequency. If they know exactly the frequency of the incident light, it will be much easier to look for those frequencies close to it, which should arise during scattering. In addition, the theory suggested that observations are easier to carry out in solids, since the molecules in them are located much closer than in gases, and the scattering is the greater, the denser the substance.

A painstaking search for the most suitable materials began. Finally, the choice fell on quartz crystals. Simply because large transparent quartz crystals are more readily available than any other.

Preparatory experiments lasted two years, the most pure samples of crystals were selected, the technique was improved, signs were established by which it was possible to undoubtedly distinguish scattering on quartz molecules from scattering on random inclusions, crystal inhomogeneities and impurities.

Wit and labor

Lacking powerful instrumentation for spectral analysis, the scientists chose an ingenious workaround that was supposed to make it possible to use the available instruments.

The main difficulty in this work was that much stronger light was superimposed on the weak light caused by molecular scattering, scattered by small contaminants and other defects of those crystal samples that were obtained for experiments. The researchers decided to take advantage of the fact that the scattered light formed by crystal defects and reflections from various parts of the installation exactly coincides in frequency with the incident light. They were only interested in light with a frequency changed in accordance with Mandelstam's theory. Thus, the task was to highlight light of a changed frequency caused by molecular scattering against the background of this much brighter light.

In order for the scattered light to have a magnitude available for registration, the scientists decided to illuminate the quartz with the most powerful lighting device available to them: a mercury lamp.

So, the light scattered in a crystal should consist of two parts: from a weak light of a changed frequency, due to molecular scattering (the study of this part was the goal of scientists), and from a much stronger light of an unchanged frequency, caused by extraneous causes (this part was harmful, it made research difficult).

The idea of \u200b\u200bthe method attracted by its simplicity: it is necessary to absorb light of a constant frequency and pass only light of a changed frequency into the spectral apparatus. But the frequency differences were only a few thousandths of a percent. No other laboratory in the world has had a filter capable of separating such close frequencies. However, a solution was found.

The scattered light was passed through a vessel with mercury vapor. As a result, all the "harmful" light "stuck" in the vessel, and the "useful" light passed without noticeable attenuation. In this case, the experimenters took advantage of one already known circumstance. The atom of matter, according to quantum physics, is capable of emitting light waves of only quite certain frequencies. At the same time, this atom is also capable of absorbing light. Moreover, only light waves of those frequencies that he himself can emit.

In a mercury lamp, light is emitted by mercury vapor, which glow under the influence of an electrical discharge that occurs inside the lamp. If this light is passed through a vessel that also contains mercury vapor, it will be almost completely absorbed. What the theory predicts will happen: the mercury atoms in the vessel will absorb the light emitted by the mercury atoms in the lamp.

Light from other sources, such as a neon lamp, will pass through the mercury vapor unharmed. Atoms of mercury will not even pay attention to it. The part of the light of the mercury lamp that is scattered in quartz with a change in wavelength will not be absorbed either.

It was this convenient circumstance that Mandelstam and Landsberg took advantage of.

Amazing discovery

In 1927, decisive experiments began. The scientists illuminated the quartz crystal with the light of a mercury lamp and processed the results. And ... they were surprised.

The results of the experiment were unexpected and unusual. Scientists did not find what they expected, not what was predicted by theory. They discovered a completely new phenomenon. But which one? And isn't this a mistake? In the scattered light, not expected frequencies were found, but much higher and lower frequencies. A whole combination of frequencies appeared in the spectrum of the scattered light, which were not present in the light incident on the quartz. It was simply impossible to explain their appearance by optical inhomogeneities in quartz.

A thorough check began. The experiments were carried out flawlessly. They were conceived so cleverly, perfectly and ingeniously that one could not help but admire them.

- So beautifully and sometimes brilliantly, Leonid Isaakovich sometimes simply solved very difficult technical problems that involuntarily each of us had a question: "Why did it not occur to me before?" - says one of the employees.

Various control experiments have consistently confirmed that there is no error. In the photographs of the spectrum of the scattered light, weak and, nevertheless, quite obvious lines persisted, indicating the presence of "extra" frequencies in the scattered light.

For many months, scientists have been looking for an explanation for this phenomenon. Where did the “alien” frequencies come from in the diffused light ?!

And the day came when Mandelstam was struck by an amazing guess. It was an amazing discovery, the one that is now considered one of the most important discoveries of the 20th century.

But both Mandelstam and Landsberg came to the unanimous decision that this discovery can be published only after a solid check, after an exhaustive penetration into the depths of the phenomenon. The final experiments began.

With the help of the sun

On February 16, Indian scientists C.N. Raman and K.S. Krishnan sent a telegram from Calcutta to this magazine with a short description of his discovery.

In those years, letters about various discoveries flocked to the journal "Priroda" from all over the world. But not every message is destined to cause excitement among scientists. When the issue with a letter from Indian scientists came out of print, physicists were very excited. The very title of the note - "A new type of secondary radiation" - aroused interest. After all, optics is one of the oldest sciences, and it was not often possible to discover something unknown in it in the 20th century.

One can imagine with what interest physicists all over the world awaited new letters from Calcutta.

Their interest was to a large extent fueled by the very personality of one of the authors of the discovery, Raman. This is a man of a curious fate and an outstanding biography, very similar to Einstein's. Einstein in his youth was a simple gymnasium teacher, and then an employee of the patent office. It was during this period that he completed the most significant of his works. Raman, a brilliant physicist, also after graduating from university was forced to serve in the department of finance for ten years, and only after that was invited to the department of the University of Calcutta. Raman soon became the recognized head of the Indian School of Physics.

Not long before the events described, Raman and Krishnan were carried away by an interesting task. Then the passions caused in 1923 by the discovery of the American physicist Compton, who, studying the passage of X-rays through matter, discovered that some of these rays, scattering away from the original direction, increase their wavelength, had not yet subsided. Translated into the language of optics, we can say that X-rays, colliding with the molecules of the substance, changed their "color".

This phenomenon was easily explained by the laws of quantum physics. Therefore, Compton's discovery was one of the decisive proofs of the correctness of the young quantum theory.

Something similar, but in optics, we decided to try. discover Indian scientists. They wanted to pass light through the substance and see how its rays will be scattered on the molecules of the substance and whether their wavelength will change.

As you can see, willingly or unwillingly, Indian scientists set themselves the same task as Soviet scientists. But their goals were different. In Calcutta, an optical analogy was sought for the Compton effect. In Moscow - an experimental confirmation of Mandelstam's prediction of frequency change in the scattering of light by fluctuating inhomogeneities.

Raman and Krishnan conceived a difficult experience because the expected effect was to be extremely small. The experiment required a very bright light source. And then they decided to use the sun, collecting its rays with a telescope.

The diameter of his lens was eighteen centimeters. The researchers sent the collected light through a prism to the vessels, which contained liquids and gases, carefully cleaned of dust and other contaminants.

But it was hopeless to detect the expected small elongation of the scattered light using white sunlight, which contains almost all possible wavelengths. Therefore, scientists decided to use light filters. They put a blue-violet filter in front of the lens, and observed the scattered light through a yellow-green filter. They rightly decided that what the first filter misses will get stuck in the second. After all, the yellow-green filter absorbs the blue-violet rays transmitted by the first filter. And both, placed one after the other, must absorb all the incident light. If any rays get into the eye of the observer, then we can say with confidence that they were not in the incident light, but were born in the substance under study.

Columbus

Indeed, in the diffused light, Raman and Krishnan found rays passing through the second filter. They recorded extra frequencies. This, in principle, could be the optical Compton effect. That is, when scattered by the molecules of the substance in the vessels, the blue-violet light could change its color and become yellow-green. But this still had to be proved. There could be other reasons for the appearance of a yellow-green light. For example, it could appear as a result of luminescence - a weak glow that often occurs in liquids and solids under the influence of light, heat, and other reasons. Obviously, there was one thing - this light was born again, it was not contained in the incident light.

The scientists repeated their experiment with six different liquids and two types of vapor. They made sure that neither luminescence nor other reasons play a role here.

The fact that the wavelength of visible light increased when it was scattered in matter seemed to Raman and Krishnan to be established. The search for them seemed to be crowned with success. They found an optical analogy to the Compton effect.

But in order for the experiments to have a finished form and the conclusions were sufficiently convincing, one more part of the work had to be done. It was not enough to detect the change in wavelength. It was necessary to measure the magnitude of this change. The first helped to make a light filter. He was powerless to do the second. Here, scientists needed a spectroscope - a device that allows you to measure the wavelength of the light under study.

And the researchers started the second part, no less difficult and painstaking. But she also met their expectations. The results again confirmed the conclusions of the first part of the work. However, the wavelength turned out to be unexpectedly long. Much more than expected. The researchers were not embarrassed by this.

How not to remember here about Columbus? He strove to find a sea route to India and, seeing the land, did not doubt that he had achieved his goal. Did he have reason to doubt his confidence in the sight of the Redskins and the unfamiliar nature of the New World?

Didn't Raman and Krishnan, seeking to detect the Compton effect in visible light, think they found it by examining the light that passed through their liquids and gases ?! Did they doubt when measurements showed an unexpectedly larger change in the wavelength of the scattered rays? What conclusion did they draw from their discovery?

According to Indian scholars, they found what they were looking for. On March 23, 1928, a telegram flew to London with an article entitled "Optical Analogy of the Compton Effect." Scientists wrote: "Thus, the optical analogy of the Compton effect is obvious, except that we are dealing with a change in wavelength much larger ..." Note: "much larger ..."

Dance of atoms

Raman and Krishnan's work was greeted with a standing ovation among scholars. Everyone rightly admired their experimental art. For this discovery, Raman was awarded the Nobel Prize in 1930.

A photograph of the spectrum was attached to the letter of Indian scientists, in which the lines depicting the frequency of the incident light and the light scattered by the molecules of the substance took their places. This photograph, according to Raman and Krishnan, illustrated their discovery more clearly.

When Mandelstam and Landsberg looked at this photo, they saw an almost exact copy of the photo they had taken! But when they got acquainted with her explanation, they immediately realized that Raman and Krishnan were wrong.

No, it was not Indian scientists who discovered the Compton effect, but a completely different phenomenon, the same one that Soviet scientists have been studying for many years ...

While the excitement caused by the discovery of Indian scientists was growing, Mandelstam and Landsberg were finishing control experiments, summing up the last decisive results.

And on May 6, 1928, they sent an article to print. A photograph of the spectrum was attached to the article.

Briefly setting out the history of the issue, the researchers gave a detailed interpretation of the phenomenon they discovered.

So what was this phenomenon that made many scientists suffer and break their heads?

Mandelstam's deep intuition and clear analytical mind immediately prompted the scientist that the detected changes in the frequency of the scattered light could not be caused by those intermolecular forces that equalize the random repetitions of air density. It became clear to the scientist that the reason undoubtedly lies within the molecules of the substance themselves, that the phenomenon is caused by intramolecular vibrations of the atoms that form the molecule.

Such fluctuations occur with a much higher frequency than those that accompany the formation and resorption of random inhomogeneities in the medium. It is these vibrations of atoms in molecules that affect the scattered light. Atoms, as it were, mark it, leave their traces on it, encrypt it with additional frequencies.

It was a most beautiful guess, a daring intrusion of human thought beyond the cordon of a small fortress of nature - a molecule. And this intelligence has brought the most valuable information about its internal structure.

Hand in hand

So, when trying to detect a small change in the frequency of scattered light caused by intermolecular forces, a larger change in frequency caused by intramolecular forces was found.

Thus, to explain the new phenomenon, which received the name "Raman scattering of light", it was enough to supplement the theory of molecular scattering, created by Mandelstam, with data on the influence of vibrations of atoms inside molecules. The new phenomenon was discovered as a result of the development of Mandelstam's idea, formulated by him back in 1918.

Yes, not without reason, as Academician S.I. Vavilov, “Nature endowed Leonid Isaakovich with a completely unusual, perspicacious, subtle mind, which immediately noticed and understood the main thing, which the majority passed by indifferently. This is how the fluctuation essence of light scattering was understood, and the idea of \u200b\u200bchanging the spectrum during light scattering appeared, which became the basis for the discovery of Raman scattering. "

Subsequently, enormous benefits were derived from this discovery, and it received valuable practical applications.

At the moment of its discovery, it seemed only the most valuable contribution to science.

What about Raman and Krishnan? How did they react to the discovery of Soviet scientists, and to their own too? Did they understand what they discovered?

The answer to these questions is contained in the following letter from Raman and Krishnan, which they sent to the press 9 days after the publication of the article by Soviet scientists. Yes, they understood - the phenomenon they observed was not the Compton effect. This is Raman scattering of light.

After the publication of the letters of Raman and Krishnan and the articles of Mandelstam and Landsberg, it became clear to scientists all over the world that one and the same phenomenon was independently and practically simultaneously made and studied in Moscow and Calcutta. But Moscow physicists studied it in quartz crystals, and Indian ones in liquids and gases.

And this parallelism, of course, was not accidental. She speaks about the urgency of the problem, its great scientific importance. It is not surprising that the results, close to the conclusions of Mandelstam and Raman at the end of April 1928, were independently obtained by the French scientists Rocard and Kaban. After a while, scientists remembered that back in 1923, the Czech physicist Smekal theoretically predicted the same phenomenon. Following the work of Smekal, the theoretical studies of Kramers, Heisenberg, Schrödinger appeared.

Apparently, only a lack of scientific information can explain the fact that scientists in many countries worked on solving the same problem, without even knowing about it.

Thirty seven years later

Raman scattering studies have not only opened a new chapter in the science of light. At the same time, they gave powerful weapons to technology. The industry has got a great way to study the properties of a substance.

After all, the frequencies of Raman scattering of light are imprints that are superimposed on the light by the molecules of the medium that scatter the light. And in different substances these prints are not the same. This is what gave Academician Mandelstam the right to call Raman scattering of light "the language of molecules." Those who are able to read the traces of molecules on the rays of light, determine the composition of the scattered light, molecules, using this language, will tell about the secrets of their structure.

The negative of the photograph of the combination spectrum contains nothing but lines of different blackness. But from this photo, the specialist will calculate the frequencies of intramolecular vibrations that appeared in the scattered light after it passed through the substance. The picture will tell about many hitherto unknown aspects of the inner life of molecules: about their structure, about the forces that bind atoms into molecules, about the relative movements of atoms. By learning to decipher Raman spectrograms, physicists learned to understand the kind of "light language" that molecules use to tell about themselves. So the new discovery made it possible to penetrate deeper into the internal structure of molecules.

Today physicists use Raman scattering to study the structure of liquids, crystals and vitreous substances. Chemists use this method to determine the structure of various compounds.

Methods for studying matter, using the phenomenon of Raman scattering of light, were developed by employees of the laboratory of the P.N. Lebedev of the USSR Academy of Sciences, headed by Academician Landsberg.

These methods allow, in a factory laboratory, to quickly and accurately perform quantitative and qualitative analyzes of aviation gasolines, cracked products, refined petroleum products and many other complex organic liquids. To do this, it is enough to illuminate the substance under study and determine the composition of the light scattered by it with a spectrograph. It seems very simple. But before this method turned out to be really convenient and fast, scientists had to work a lot on creating accurate, sensitive equipment. And that's why.

Of the total amount of light energy entering the substance under study, only an insignificant part - about one ten-billionth - is scattered light. And the Raman scattering rarely accounts for even two or three percent of this value. This is probably why the Raman scattering itself remained unnoticed for a long time. And it is not surprising that obtaining the first Raman photographs required exposures lasting tens of hours.

Modern equipment, created in our country, makes it possible to obtain a combination spectrum of pure substances within a few minutes, and sometimes even seconds! Even for the analysis of complex mixtures, in which individual substances are included in an amount of several percent, an exposure of no more than an hour is usually sufficient.

Thirty-seven years have passed since the language of molecules, recorded on photographic plates, was discovered, deciphered and understood by Mandelstam and Landsberg, Raman and Krishnan. Since then, the whole world has been working hard to compile a "dictionary" of the language of molecules, which optics call the catalog of Raman frequencies. When such a catalog is compiled, the interpretation of spectrograms will be greatly facilitated and the Raman scattering of light will become even more fully at the service of science and industry.

Municipal budgetary educational institution

"Kislovskaya secondary school" of the Tomsk region

Research work

Topic: "Why is the sunset red ..."

(Light dispersion)

Work completed: ,

student of grade 5A

Head;

chemistry teacher

1. Introduction ………………………………………………… 3

2. Main part …………………………………………… 4

3. What is light …………………………………………… .. 4

Study subject - sunset and sky.

Research hypotheses:

The sun has rays that color the sky in different colors;

Red can be obtained under laboratory conditions.

The relevance of my topic lies in the fact that it will be interesting and useful for listeners because so many people look at the clear blue sky, admire it, and few know why it is so blue during the day, and at sunset it is red and what gives such a color to him.

2. Main part

At first glance, this question seems simple, but in fact it touches on the deepest aspects of the refraction of light in the atmosphere. Before you can understand the answer to this question, you need to have an idea of \u200b\u200bwhat light is..jpg "align \u003d" left "height \u003d" 1 src \u003d "\u003e

What is light?

Sunlight is energy. The heat of the sun's rays, focused by the lens, turns into fire. Light and heat are reflected by white surfaces and absorbed by black ones. This is why white clothes are colder than black ones.

What is the nature of light? Isaac Newton was the first to try seriously to study light. He believed that light consists of particles of corpuscles, which are fired like bullets. But some of the characteristics of light could not be explained by this theory.

Another scientist, Huygens, offered a different explanation for the nature of light. He developed a "wave" theory of light. He believed that light creates impulses, or waves, in the same way that a stone thrown into a pond creates waves.

What views do scientists hold today on the origin of light? It is now believed that light waves have the characteristics of both particles and waves at the same time. Experiments are being carried out to confirm both theories.

Light consists of photons - weightless particles that do not have mass, travel at a speed of about 300,000 km / s and have wave properties. The frequency of wave vibrations of light determines its color. In addition, the higher the vibration frequency, the shorter the wavelength. Each color has its own vibration frequency and wavelength. White sunlight is made up of many colors that can be seen by refracting it through a glass prism.

1. Prism decomposes light.

2. White light is complex.

If you look closely at the passage of light through a triangular prism, you can see that the decomposition of white light begins as soon as the light passes from air to glass. Instead of glass, you can take other materials transparent to light.

It is remarkable that this experience has survived for centuries, and its methodology is still used in laboratories without significant changes.

dispersio (lat.) - dispersion, dispersion - dispersion

Newton's variance.

I. Newton was the first to study the phenomenon of light dispersion and is considered one of his most important scientific achievements. No wonder on his tombstone, erected in 1731 and decorated with figures of young men who hold the emblem of his major discoveries, one figure is holding a prism, and the inscription on the monument contains the words: "He investigated the difference between light rays and the various properties that appear at the same time, which no one previously suspected." The last statement is not entirely accurate. Dispersion was known earlier, but it has not been studied in detail. Improving telescopes, Newton drew attention to the fact that the image given by the lens is colored at the edges. Investigating refractive-colored edges, Newton made his discoveries in the field of optics.

Visible spectrum

When a white ray is decomposed in a prism, a spectrum is formed in which radiation of different wavelengths is refracted at different angles. The colors included in the spectrum, that is, those colors that can be obtained by light waves of the same length (or very narrow range), are called spectral colors. The main spectral colors (which have their own name), as well as the emission characteristics of these colors, are presented in the table:

Each “color” in the spectrum must be associated with a light wave of a certain length

The simplest idea of \u200b\u200bthe spectrum can be obtained by looking at a rainbow. White light, refracting in water droplets, forms a rainbow, since it consists of many rays of all colors, and those are refracted in different ways: red - the weakest, blue and violet - the strongest. Astronomers study the spectra of the Sun, stars, planets, comets, since a lot can be learned from the spectra.

Nitrogen "href \u003d" / text / category / azot / "rel \u003d" bookmark "\u003e nitrogen. Red and blue light interact differently with oxygen. Since the wavelength of blue is roughly the size of an oxygen atom and because of this, blue light is scattered by oxygen in different directions, while red light quietly passes through the atmospheric layer.In fact, violet light is scattered even more in the atmosphere, but the human eye is less susceptible to it than to blue light. As a result, it turns out that the eye a person from all sides catches the blue light scattered by oxygen, which makes the sky seem blue to us.

Without an atmosphere on Earth, the Sun would appear to us as a bright white star, and the sky would be black.

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Unusual phenomena

https://pandia.ru/text/80/039/images/image008_21.jpg "alt \u003d" (! LANG: Aurora Borealis" align="left" width="140" height="217 src=">!} Polar lights Since ancient times, people have admired the majestic picture of the aurora and wondered about their origin. One of the earliest mentions of aurora is found in Aristotle. In his "Meteorology", written 2300 years ago, you can read: "Sometimes on clear nights many phenomena are observed in the sky - gaps, gaps, blood-red color ...

It looks like a flame is on fire. "

What does a ray clear at night flicker?

What does a thin flame strike the firmament?

Like lightning without formidable clouds

Striving from the ground to the zenith?

How can it be that a frozen ball

Was there a fire in the middle of winter?

What is aurora borealis? How is it formed?

Answer. The aurora is a luminescent glow that occurs as a result of the interaction of charged particles (electrons and protons) flying from the Sun with atoms and molecules of the earth's atmosphere. The appearance of these charged particles in certain regions of the atmosphere and at certain altitudes is the result of the interaction of the solar wind with the Earth's magnetic field.

Aerosol "href \u003d" / text / category / ayerozolmz / "rel \u003d" bookmark "\u003e aerosol scattering of dust and moisture, they are the main reason for the decomposition of solar color (dispersion). occurs almost at a right angle, their layer between the eyes of the observer and the sun is insignificant.The lower the sun descends to the horizon line, the more the thickness of the atmospheric air layer and the amount of aerosol suspension in it increase.The sun's rays, relative to the observer, change the angle of incidence on particles of suspension, then the dispersion of sunlight is observed.So, as mentioned above, sunlight consists of seven primary colors. Each color, like an electromagnetic wave, has its own length and ability to scatter in the atmosphere. The basic colors of the spectrum are arranged in a scale in order, from red to The color red has the least ability to scatter (hence, absorb) in the atmosphere. dispersion all colors that follow the red on the scale are scattered by the components of the aerosol suspension and are absorbed by them. The observer only sees red. This means that the thicker the atmospheric air layer, the higher the suspended matter density, the more spectrum rays will be scattered and absorbed. A well-known natural phenomenon: after the powerful eruption of the Krakatoa volcano in 1883, unusually bright, red sunsets were observed in different places of the planet for several years. This is due to the powerful release of volcanic dust into the atmosphere during the eruption.

I don't think my research will end there. I still have questions. I want to know:

What happens when rays of light pass through various liquids, solutions;

How light is reflected and absorbed.

Having completed this work, I was convinced how much surprising and useful for practical activity can be in the phenomenon of light refraction. It was this that allowed me to understand why the sunset is red.

Literature

1., Physics. Chemistry. 5-6 cl. Textbook. M .: Bustard, 2009, p. 106

2. Bulat is a phenomenon in nature. M .: Education, 1974, 143 p.

3. "Who Makes the Rainbow?" - Quant 1988, No. 6, p. 46.

4. Lectures on optics. Tarasov in nature. - M .: Education, 1988

Internet resources:

1.http: // potomy. ru / Why is the sky blue?

2.http: // www. voprosy-kak-i-pochemu. ru Why is the sky blue?

3.http: // expirience. ru / category / obrazovanie /

It is known that blue sky - this is the reason for the interaction of the ozone layer and sunlight. But what exactly is happening in terms of physics and why is the sky blue? There were several theories on this score. All of them ultimately confirm that the main reason is the atmosphere. But the interaction mechanism is also explained.

The main fact is about sunlight. Sunlight is known to be white. White is the sum of all spectra... It can be decomposed into rainbows (or spectra) when passing through a dispersion medium.

Based on this fact, scientists have proposed several theories.

The first theory explained the blue color by this scattering by particles in the atmosphere. It was assumed that a large amount of mechanical dust, particles of plant pollen, water vapor and other small inclusions work as a dispersion medium. As a result, only the bluish color spectrum reaches us. But how then to explain that the color of the sky does not change in winter or in the north, where there are fewer such particles or their nature is different? The theory was quickly dismissed.

Next theory assumed that a white light flux passes through the atmosphere, which consists of particles. When a light beam passes through their field, the particles are excited. The activated particles begin to emit additional rays. This turns the sunny color into a bluish color. In addition to mechanical scattering and dispersion, white light also activates atmospheric particles. The phenomenon resembles luminescence. At the moment, this explanation is.

The latest theory the most simple and it is sufficient to explain the main cause of the phenomenon. Its meaning is very similar to previous theories. Air is capable of scattering light across spectra. This is the main reason for the blue glow. Light with short wavelengths is scattered more intensely than light with short wavelength. Those. violet is more diffused than red. This fact explains the change in the color of the sky at sunset. It is enough to change the angle of the sun. This is what happens when the earth rotates, and the color of the sky changes to orange-pink at sunset. The higher the sun is above the horizon, the bluer the light we will see. The reason for everything is the same dispersion or the phenomenon of the decomposition of light into spectra.

In addition to all this, you need to understand that all the above factors cannot be excluded. After all, each of them makes some contribution to the overall picture. For example, a few years ago in Moscow, as a result of abundant flowering of plants in the spring, a dense cloud of pollen was formed. It colored the sky green. This is a rather rare phenomenon, but it shows that the rejected theory about microparticles in air also takes place. True, this theory is not exhaustive.