How is a rainbow formed? All about the rainbow as a physical phenomenon.

Instruction

As Newton established, a white light ray is produced by the interaction of the rays different color: red, orange, yellow, green, blue, blue, purple. Each color is characterized by a specific wavelength and vibration frequency. At the boundary of transparent media, the speed and length of light waves change, the oscillation frequency remains the same. Each color has its own refractive index. The red beam deviates the least from the previous direction, orange a little more, then yellow, etc. The highest coefficient refraction has a violet ray. If a glass prism is installed in the path of a light beam, then it will not only deviate, but also break up into several rays of different colors.

And now . In nature, the role of a glass prism is played by raindrops that the sun's rays collide with when passing through the atmosphere. Since the density of water is greater, the light beam at the boundary of two media is refracted and decomposed into components. Further, the color rays move already inside the drop until they collide with its opposite wall, which is also the boundary of two media, and, moreover, has mirror properties. Most of the light flux after the secondary refraction will continue to move in the air behind the raindrops. Some part of it will be reflected from rear wall drops in and out air environment after secondary refraction on its front surface.

This process occurs simultaneously in many drops. To see a rainbow, the observer must stand with his back to the Sun and face the wall of rain. Spectral rays emerge from raindrops under different angles. Only one ray enters the observer's eye from each drop. Rays emerging from neighboring drops merge, forming an arc. Thus, from the uppermost drops, rays of red color enter the eye of the observer, from those below - orange, and so on. Violet rays are the strongest. The purple stripe will be the bottom. A rainbow in shape can be seen when the Sun is at an angle of no more than 42° relative to the horizon. The higher the sun rises, the smaller sizes rainbows.

In fact, the described process is somewhat more complicated. The light beam inside the drop is reflected multiple times. In this case, not one color arc can be observed, but two - a rainbow of the first and second order. The outer arc of the first-order rainbow is colored red, the inner arc purple. In a second-order rainbow, the opposite is true. It usually looks much paler than the first, since the intensity of the light flux decreases with multiple reflections.

Much less often, three, four and even five colored arcs can be observed in the sky at the same time. This was observed, for example, by residents of Leningrad in September 1948. This is because rainbows can also occur in reflected sunlight. Such multiple color arcs can be observed over a wide area. water surface. In this case, the reflected rays go from bottom to top,

As in the midst of transparent cloudy shrouds

Above the onion, the onion is inflorescence and circumferential

Exalted by the messenger of Juno,

And formed by the inner outer.

The rainbow is in plain sight - it is usually observed in the form of two colored arcs (two inflorescences, which Dante writes about), and in the upper arc the colors are arranged in this order from top to bottom: purple, blue, cyan, green, yellow, orange, red , and in the lower arc, on the contrary, from red to purple. To memorize their sequence, there are mnemonic phrases, the first letters of each word in which correspond to the first letters of the color name. For example, this is the phrase "Every Hunter Wants to Know Where the Pheasant Sits" or another, no less famous, "How Once Jean the Bell Ringer Hit the Lantern with His Head ". True, the tradition of distinguishing 7 colors in the rainbow is not universal. For example, Bulgarians have 6 colors in the rainbow.

rainbow gives unique opportunity watch in vivo decomposition of white light into a spectrum.

Rainbows usually appear after rain, when the Sun is fairly low. Somewhere between the Sun and the observer, it is still raining. Sunlight, passing through water drops, is repeatedly reflected and refracted in them, as in small prisms, and rays of different colors come out of the drops at different angles. This phenomenon is called dispersion (i.e. decomposition) of light. As a result, a bright colored arc is formed (but it is actually steep; you can see it in its entirety from an airplane).

Sometimes two are observed at once, less often - three multi-colored arcs. The first rainbow is created by rays reflected inside the drops once, the second - by rays reflected twice, etc. In 1948 in Leningrad (now St. Petersburg), four rainbows appeared at once among the clouds over the Neva.

The type of rainbow, the brightness of the colors, the width of the stripes depend on the size and number of water droplets in the air. bright rainbow happens in the summer after a thunderstorm, during which large drops fall. As a rule, such a rainbow portends good weather.

On a bright moonlit night, you can see a rainbow from the moon. A rainbow appears in the light of a full moon when it's raining. Since human vision is designed so that in low light the most sensitive receptors of the eye - "rods" - do not perceive colors, the lunar rainbow looks whitish; the brighter the light, the "colorier" the rainbow (color receptors - "cones" are included in its perception).

fiery rainbow

She was lucky to see a resident of Sweden, Marian Erikson. The rainbow stretched across the night sky and stood at full moon within a minute.

Signs and legends.

Once upon a time, a person began to wonder why rainbows appear in the sky. In those days, they didn’t even hear about optics. Therefore, people invented myths and legends, and there were also many signs. Here are some of them:

• In Scandinavian mythology, the rainbow is the Bifrost Bridge, connecting Midgard (the world of people) and Asgard (the world of the gods).
• In ancient Indian mythology - the bow of Indra, the god of thunder and lightning.
• AT ancient Greek mythology- the road of Irida, messenger between the worlds of gods and people.
• According to Slavic beliefs, a rainbow, like a snake, drinks water from lakes, rivers and seas, which then rains.
• An Irish leprechaun hides a pot of gold where the rainbow touched the ground.
• According to Chuvash beliefs, if you pass through a rainbow, you can change gender.
• In the Bible, the rainbow appeared after the Flood as a symbol of the forgiveness of mankind.
• Superstitious people believed that the rainbow is a bad omen. They believed that the souls of the dead pass into the other world along the rainbow, and if a rainbow appeared, this means someone's imminent death.

The history of the explanation of the rainbow.

Already Aristotle, ancient Greek philosopher, tried to explain the reason for the rainbow. And the Persian astronomer Qutb al-Din al-Shirazi (1236-1311), and perhaps his student Kamal al-din al-Farisi (1260-1320), was apparently the first to give a sufficiently accurate explanation of the phenomenon.

The general physical picture of the rainbow was already clearly described by Mark Antony de Dominis (1611).

M.A. de Dominis

Based on experimental observations, he came to the conclusion that a rainbow is obtained as a result of reflection from inner surface raindrops and double refraction - at the entrance to the drop and at the exit from it. René Descartes gave a fuller explanation of the rainbow in his Meteora in the chapter On the Rainbow (1635).

Rene Descartes

Descartes writes:

“Firstly, when I took into account that a rainbow can appear not only in the sky, but also in the air near us, every time there are drops of water in it, illuminated by the sun, as is sometimes seen in fountains, it is easy for me it was concluded that it depends on how the rays of light act on these drops, and from them reach our eyes; further, knowing that these drops are spherical, and seeing that both with large and small drops, the rainbow always appears in the same way , I set myself the goal of creating a very large drop in order to be able to see it better. To do this, I filled a large glass vessel, quite round and completely transparent with water, and came to the following conclusion ... "

This conclusion repeats and refines the result obtained by Dominis. In particular, Descartes discovered that the second (outer) rainbow results from two refractions and two reflections. He also qualitatively explained the appearance of rainbow colors by comparing the refraction of light in a drop with refraction in a glass prism. Figure 1, which explains the path of a ray in a drop, is taken from the work of Descartes mentioned above. But the main merit of Descartes was that he quantitatively explained this phenomenon, for the first time using the law of refraction of light:

"I did not yet know why colors appear only at certain angles, until I took a pen and calculated in detail the course of all the rays that fall on different points of the water drop, in order to find out at what angles they can enter our eye after two refractions. and one or two reflections, I then found that after one reflection and two refractions, there are many more rays that can be seen at an angle from 41° to 42° (with respect to the sunbeam) than those that can be seen under any smaller angle, and there is not one that would be visible at a larger one.Furthermore, I also found that after two reflections and two refractions, there are many more rays that fall into the eye at an angle from 51 ° to 52 ° than those that would fall at any greater angle, and there are none at all that would fall at a lesser one.

Thus, Descartes not only calculates the path of the rays, but also determines the angular distribution of the intensity of the light scattered by the drops.

With regard to colors, the theory was supplemented by Isaac Newton.

Isaac Newton

Although the multi-color spectrum of the rainbow is continuous, according to tradition, 7 colors are distinguished in it. It is believed that Isaac Newton was the first to choose the number 7, for which the number 7 had a special symbolic meaning(for Pythagorean, theological or morological reasons).

In the well-known Lectures on Optics, which were written in the 1570s but published after Newton's death in 1729, the following summary is given:
"Of the rays entering the ball, some leave it after one reflection, others after two reflections; there are rays emerging after three reflections and even more reflections. Since raindrops are very small relative to the distance to the observer's eye, it is not worth considering their size at all, but only the angles formed by the incident rays with the outgoing ones. Where these angles are largest or smallest, the outgoing rays are most concentrated. As various genera rays (rays different colors) make up different largest and smallest angles, then the rays that gather most densely at different places tend to manifest their own colors.

Newton's statement about the possibility of not taking into account the size of the drop, as well as the words of Descartes that the rainbow always appears in the same way with large and small drops, turned out to be inaccurate. A complete theory of the rainbow, taking into account the diffraction of light, which depends on the ratio of the wavelength of light and the size of the drop, was built only in the 19th century by J.B. Airy (1836) and J.M. Pernter (1897).

Refraction and reflection of a ray in a drop of water.

The drawing of Descartes, which we reproduced as a relic, has one "methodological" imperfection. To an unprepared reader it may seem that both rainbows, external and internal, are due to different ways reflections in the same drop. It would be better to depict two drops: one related to the lower rainbow, the other to the upper one, leaving each with one way of reflection, as shown in Fig. 2. For ease of perception, in both cases the direction of the sunbeam incident on the droplet is taken as the abscissa axis. The y coordinate characterizing the point of incidence of the beam on the droplet will be called the impact parameter.

From fig. 2a, it can be seen that an incident ray with one reflection can be perceived by an observer only if the point of incidence belongs to the upper part of the drop (y > 0). On the contrary, with two reflections this will be possible for those rays that fall on lower part drops (y< 0).

Let us first assume that the drop is in a vertical plane passing through the position of the Sun and the observer's eye. Then the incident, refracted and reflected rays lie in the same plane. If α 1 is the angle of incidence, and α 2 is the angle of refraction, then from fig. 2, a and b, the angle of the emerging beam with respect to the incident one in the first case will be equal to φ 1 = 4α 2 -2α 1 (1)
and in the second - φ 2 = π - 6α 2 + 2α 1 (2)
moreover, according to the law of refraction: sin α 2 = sin α 1 / n
where n in our case is the refractive index of water. In addition, assuming conditionally the radius of the drop as a unit of length, we have:

Accordingly, in the first and second cases. Therefore, from (1) and (2) we obtain
φ 1 =4 arcsin(y/n) - 2 arcsin y, y>0 (3)
φ 2 \u003d π + 6 arcsin (y / n) - 2 arcsin y, y<0 (4)

These two equations are the main ones for further consideration. It is easy to plot the angles φ 1 and φ 2 as functions of y. They are shown in fig. 3 for refractive index n=1.331 (red). We see that at the value of the impact parameter y≈0.85, the maximum of the angle φ 1 is reached, approximately equal to 42°, and the angle has a minimum of ~53° at y≈-0.95. Let us show that these extremal points correspond to the maximum intensity of the light reflected by the drop.

Let us consider some small range of change of the impact parameter (for definiteness in the first case) y, y + Δy. Using the graph, you can find the change in the angle φ in this interval Δφ. On fig. 3 shows that Δφ=Δy*tg β, where β is the angle that the tangent to the graph at a given point forms with the x-axis. The value of Δy is proportional to the intensity of light ΔI incident on the drop in this interval of the impact parameter. The same light intensity (more precisely, a value proportional to it) is scattered by the drop in the angular interval Δφ. We can write ΔI ~ Δy =Δy*ctg β. Therefore, the intensity of the light scattered by the drop per unit angle of scattering can be expressed as I(φ) = ΔI/Δφ ~ ctg β (5)

Since at the extreme points ctg β = ∞, the value (5) goes to infinity. Note that the positions of these extreme points for different colors are somewhat different, which makes it possible to observe the rainbow.

How to draw a rainbow

Now we can draw a diagram of the observation of the rainbow. Such a construction is shown in Fig. 4. First, draw the surface of the Earth and the observer standing on it. In front of the observer is a curtain of rain (shaded in grey). Then we depict the sun's rays, the direction of which depends on the height of the Sun above the horizon. We pass red and violet rays through the observer's eye at the above angles with respect to the sun's rays. One can be sure, on the basis of the results of the previous section, that these rays will arise as a result of scattering by the corresponding raindrops. At the same time, as follows from Fig. 2, the lower rainbow is due to scattering processes with one reflection, and the upper one - with two reflections. Pay attention to the alternation of colors: violet rays are external, and red rays are internal. It is obvious that rays of other colors in each rainbow are placed between red and violet in accordance with the values ​​of the refractive indices.

Recall that we have so far considered the image of a rainbow in a vertical plane passing through the eye of the observer and the position of the Sun. Let's draw a straight line passing through the eye of the observer parallel to the sun's beam. If the vertical plane is rotated around the indicated straight line, then its new position for observing the rainbow will be completely equivalent to the original one. Therefore, the rainbow has the shape of an arc of a circle, the center of which is located on the constructed axis. The radius of this circle (as seen in Fig. 4) is approximately equal to the observer's distance from the rain curtain.

Note that when observing a rainbow, the Sun should not be too high above the horizon - no more than 53.48 °. Otherwise, the pattern of rays in the figure will rotate clockwise, so that even the violet ray of the upper rainbow cannot reach the eye of an observer standing on the Earth. True, this will be possible if the observer rises to a certain height, for example, by plane. If the observer rises high enough, he will be able to see the rainbow in the form of a complete circle.

Rainbow Formation Diagram

Rainbow Formation Diagram
1) spherical a drop 2) internal reflection 3) primary rainbow
4) refraction 5) secondary rainbow 6) incoming beam of light
7) the course of the rays during the formation of the primary rainbow

8) the course of rays during the formation of a secondary rainbow
9) observer 10) primary rainbow formation area
11) secondary rainbow formation area 12) droplet cloud

This description of the rainbow should be clarified taking into account the fact that the sun's rays are not strictly parallel. This is due to the fact that the rays falling on the drop from different points of the Sun have slightly different directions. The maximum angular divergence of the rays is determined by the angular diameter of the Sun, which is known to be approximately 0.5°. What does this lead to? Each drop emits into the eye of the observer not so monochromatic light as it would be in the case of strict parallelism of the incident rays. If the angular diameter of the Sun were noticeably greater than the angular distance between the violet and red rays, then the colors of the rainbow would be indistinguishable. Fortunately, this is not the case, although, undoubtedly, the overlapping of rays with different wavelengths affects the contrast of the colors of the rainbow. Interestingly, the finiteness of the angular diameter of the Sun was already taken into account in the work of Descartes.

Among other optical phenomena in the atmosphere, the rainbow, in its expressiveness and beauty, is one of the most remarkable, frequent and widely known. In its appearance, it is a multi-colored arc against the background of rain clouds located on the side opposite to the Sun. A rainbow is formed only when, with the above arrangement of the Sun and rain clouds, rain falls from the latter, and the larger the drops, the clearer and brighter the rainbow will be, and, conversely, with small drops of rain, it becomes whitish, hardly noticeable or not visible at all. The arrangement and alternation of colors in the rainbow is always the same: the outer (upper) edge is colored red, then orange, yellow, green, and the lower edge is purple.

The formation of a rainbow is explained by refraction, internal reflection and decomposition into component colors of the sun's rays in raindrops. The sunbeam, going inside the drop, experiences the first partial refraction and decomposition. Having reached the rear inner wall of the drop, it experiences total internal reflection and, leaving the drop, is again refracted and decomposed into composite colored rays. Since the angle of refraction of rays of different colors is not the same, a beam of not parallel, but divergent colored rays comes out of each drop. Red rays deviate least of all and violet rays most of all. Therefore, from the drops located above, red rays will fall into the eye of the observer, and from the drops located below, rays with a large refraction (deviation) angle will fall, which include orange, yellow, etc., and the latter - violet. Thus, the observer will see the vertical spectrum of sunlight formed by raindrops.

When the Sun is on the horizon, the rainbow looks like a half circle with an angular radius of about 41°. As the Sun rises, the rainbow descends, and when it is at 41-42°, the rainbow will disappear. For this reason, in temperate and tropical sprats around noon, the appearance of a rainbow, under all other favorable conditions, is impossible.

Sometimes there is a double rainbow (one above the other), and in the upper (secondary) rainbow, the colors alternate in reverse order.

A rainbow appears in the evening or morning, most often after the last rain. It is only an indirect sign of one or another size of raindrops, in other words, strong or weak rain falling away from the observer.

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Introduction

The relevance of the work

In the summer, I often went with my parents to the garden, which is located outside the city. One evening, we were sitting and having dinner on the street, suddenly the clouds thickened, and it began to rain. We hid under a canopy and watched the surrounding nature. It smelled of wet earth, grass, and the air became clean and fresh. And then the rain subsided, in some places blue gaps appeared in the sky, the sun's rays slipped through them. And suddenly, a multi-colored arc spread across the entire sky, like a huge gate in the sky. Yes, not one, but two! We were all very happy, began to admire and photograph the double rainbow. But for a short time we were pleased with the rainbow with its beauty.

Rainbow is one of the most beautiful natural phenomena. How much joy it brings to both children and adults. Her appearance evokes positive emotions, cheers up people. Konstantin Dmitrievich Ushinsky has a fable "The Sun and the Rainbow". “Once after the rain, the sun came out, and a seven-colored rainbow arc appeared. Whoever looks at the rainbow, everyone admires it. The rainbow became proud, and began to boast that it was more beautiful than the sun itself. The sun heard these speeches and says: “You are beautiful - this is true, but there is no rainbow without me.” And the rainbow only laughs and praises itself even more. Then the sun got angry and hid behind a cloud - and the rainbow was gone.” So is it really impossible for a rainbow to appear without the sun. Why there is no rainbow, in sunny weather without rain, or in rainy weather without sun.

Today, not every person can explain the appearance of a rainbow. Where does the rainbow come from? Why do her colors appear in a certain order? Why is there a double rainbow? Is it possible to get a rainbow artificially, for example, at home? To answer all these questions, I decided to do my own research.

Research hypotheses:

The rainbow appears in nature only on a sunny and rainy day;

You can get a rainbow at home using an artificial light source.

Objective:

Find out the reason for the appearance of a rainbow.

Tasks:

Define a rainbow;

Find out the conditions for the appearance of a rainbow in nature;

Find out how many colors the rainbow has and what is the solar spectrum;

Find out what rainbows are;

Try to get a rainbow at home in different ways.

Object of study: rainbow

Research methods :

Study of special literature and Internet sources;

Conducting experiments on obtaining a rainbow at home, using an artificial light source;

Analysis of the obtained results.

2. Theoretical material

2.1. What is a rainbow?

There are several theories explaining its origin. According to one of them, radoga is derived from the Proto-Slavic root radъ, the meaning of which is similar to the Anglo-Saxon rot (joyful, noble).

Some language researchers tend to assume that the word "rayduga", as this word is pronounced in a number of dialects of the modern Russian language, has a folk etymology, was formed as a result of the merger of the words "paradise" and "duga". It also sounded in Russian in the 17-18 centuries. In this case, the rainbow literally means "motley arc."

In Slavic myths and legends, a rainbow was considered a magical heavenly bridge thrown from heaven to earth, a road along which angels descend from heaven to draw water from rivers. They pour this water into the clouds, and from there it falls as life-giving rain.

I read the meaning of the word "rainbow" in various explanatory dictionaries:

"Rainbow - multi-colored arc in the firmament, formed as a result of the refraction of the sun's rays in raindrops " (Explanatory dictionary of Ozhegov). "Rainbow- a multi-colored arc in the sky. It is observed when the Sun illuminates the curtain of rain, located on the opposite side of the sky from it. It is explained by the refraction, reflection and diffraction of light in raindrops. (Modern explanatory dictionary. Astronomical dictionary).

So, I found out that a rainbow is a multi-colored arc in the sky, formed as a result of the refraction of sunlight in raindrops.

2.2. Cause of the rainbow

Aristotle, an ancient Greek philosopher, tried to explain the reason for the appearance of a rainbow. He determined that "a rainbow is an optical phenomenon, not a material object." Aristotle suggested that rainbows result from the unusual reflection of rays of sunlight from clouds.

The phenomenon of the rainbow was explained by the refraction of the sun's rays in raindrops in 1267 by Roger Bacon.

The first to understand the cause of the rainbow was the German monk Theodoric of Freiberg, who in 1304 recreated it on a spherical flask with water. However, Theodoric's discovery was forgotten.

An attempt to explain the rainbow as a natural phenomenon was made in 1611. Archbishop Antonio Dominis. His explanation of the rainbow was contrary to the biblical one, so he was excommunicated and sentenced to death. Antonio Dominis died in prison, without waiting for execution, but his body and manuscripts were burned.

The scientific explanation of the rainbow was also given by the French philosopher, mathematician, mechanic Rene Descartes in 1637. Descartes explained the rainbow on the basis of the laws of refraction and reflection of sunlight in drops of falling rain. At that time, the decomposition of white light into a spectrum upon refraction had not yet been discovered. Therefore, Descartes' rainbow was white.

The founder of the seven-color rainbow was Isaac Newton, who revealed the reason for the appearance of the rainbow.

2.3. Refraction of rays. Range

Back in 1666, Isaac Newton proved that ordinary white light is a mixture of rays of different colors. "I darkened my room," he wrote, "and made a very small hole in the shutter to let the sunlight in." In the path of the sun's ray, the scientist placed a special triangular glass - a prism. On the opposite wall, he saw a multi-colored strip - the spectrum. Newton explained this by saying that the prism decomposed white light into its constituent colors. Newton was the first to figure out that the sun's ray is multicolored.

Rainbow is the most famous, well-known spectrum. When it rains, there are a lot of water droplets in the air. Each drop of rain plays the role of a tiny prism. The sun's rays that pass through the raindrops, as through prisms, are refracted in the raindrops. As a result of the decomposition of light rays, a large curved spectrum appears - a strip of colored lines and is reflected on the opposite side of the sky. When it rains, there are a lot of water droplets in the air. And since there are a lot of them, then the rainbow is obtained in half the sky.

Let us trace the path of the beam passing through the drop. Having refracted at the boundary of the drop, the beam enters the drop and reaches the opposite boundary. Part of the beam, having been refracted, leaves the drop, part again goes inside the drop to the next boundary. Here again, part of the beam, having been refracted, leaves the drop, and some part goes through the drop, and so on. Each white ray, refracted in a drop, decomposes into a spectrum, and a beam of divergent colored rays emerges from the drop.

There are seven colors in the solar spectrum: red, orange, yellow, green, blue, indigo and violet.

2. 4. Colors of the rainbow

And now in more detail about the colors of the solar spectrum or the rainbow. Studies have shown that the human eye distinguishes 160 shades of colors. This is because there is no clear boundary between colors, one color passes into another through all shades. The primary colors of the rainbow are red, yellow and blue. From them you can get all the other colors of the rainbow. The colors observed in the rainbow alternate in the same sequence as in the spectrum obtained by passing a beam of sunlight through a prism. In this case, the inner (facing the surface of the Earth) extreme region of the rainbow is colored purple, and the outer extreme region is red.

Sometimes as many as 2, 3, 4 rainbows are visible in the sky - one of them is very bright, the second is paler. This means that the sun's ray is twice reflected in the drops of water. At the same time, in another rainbow, the colors of the stripes are arranged in the reverse order - the upper part of the arc is purple, and the lower one is red. Second rainbows are formed due to the double reflection of sunlight inside raindrops.

Rainbow colors: red, orange, yellow, green, blue, blue, purple. And also a lot of shades between these colors, so there is no clear transition from one color to another. The colors of the rainbow are arranged in a strict sequence. To better remember their sequence, people came up with this phrase: “ To every O hotnik F does W nat, G de With goes F azan. By the first letters of the words and remember the colors. The outer edge of the arc is usually red, while the inner edge is purple.

The rainbow has always been seen differently in different periods of history and in different nations. It distinguished three primary colors, and four, and five, and as many as you like. The Australian Aboriginal Rainbow Serpent was six-colored. Some African tribes see only two colors in the rainbow - dark and light. So where did the seven colors in the rainbow come from? As I said earlier, only Newton came up with the idea of ​​analyzing light. And, first, he counted five colors. Subsequently, having seen another color (orange), he considered it a theological obsession (the number 6 for him was diabolical), trying to create a correspondence between the number of colors of the spectrum and the number of fundamental tones of the musical scale. Newton added to the six listed colors of the spectrum one more - indigo. Indigo is a variety of purple, a cross between dark blue and purple. The name comes from the indigo plant, which grows in India, from which the corresponding dye was extracted, which was used to dye clothes. So Newton became the father of the seven-color rainbow.

The division of the spectrum into seven colors took root, and the following memorizer appeared in the English language - Richard Of York Gave Battle In Vain (In - for blue indigo). And over time, they forgot about indigo and there were six colors. American children are taught the six primary colors of the rainbow. English (German, French, Japanese) too. But it's still more difficult. In addition to the difference in the number of colors, there is another problem - the colors are not the same. The Japanese, like the British, are sure that there are six colors in the rainbow. And they will be happy to name them for you: red, orange, yellow, blue, indigo and violet. Where did the green go? Nowhere, it simply does not exist in Japanese. The Japanese, rewriting Chinese characters, lost the green character (it exists in Chinese). The British will agree with the Japanese on the number of flowers, but not on the composition. The English do not have blue in their language. And if there is no word, then there is no color. American orange is by no means our orange, and often more red (in our understanding). By the way, in the case of hair color, on the contrary, red is a red color.

2.5. Fancy rainbows

In the course of my research, I learned that there are different rainbows on earth, but the most common is an ordinary rainbow. Many other optical phenomena are known to occur for similar reasons, or appear to be. Consider what rainbows are.

Lunar (night)

Rainbows can also be seen at night by moonlight. A moonbow (also known as a nightbow) is a rainbow spawned by the moon. The lunar rainbow is comparatively paler than the usual one. This is because the Moon reflects less light from the Sun than the Sun does during the day. The lunar rainbow is visible with a very bright night Sun - the Moon. At night, when the full, necessarily full, moon hangs high in the dark, necessarily dark sky, and at the same time it is raining against the moon, you may be lucky to see a night rainbow! And she, too, will appear white to us. Although in fact it is multi-colored.

Foggy (white) rainbow

A white or misty rainbow is a rainbow that is a wide, brilliant white arc. A foggy rainbow appears when the sun's rays illuminate a faint fog, consisting of very small droplets of water. Why does the rainbow appear white to us? The point is the size of the droplets from which the sun's rays are reflected. The dimensions of the fog particles are so small that the individual colored stripes, into which the sunbeam breaks up when refracted, diverge to the sides not as a wide multi-colored fan, but as a barely opened one. The colors seem to be superimposed on each other, and the eye no longer distinguishes colors, but sees only a colorless light arc - a white rainbow. A foggy rainbow can also appear at night during fog, when the moon is bright in the sky. A hazy rainbow is a rather rare atmospheric phenomenon.

inverted rainbow

An inverted rainbow is a rather rare phenomenon. . Unlike the traditional rainbow, the “smile in the sky” appears in a clear sky, without rain clouds. The rays of the sun should illuminate at a certain angle a thin, haze-like curtain of clouds at an altitude of 7 - 8 thousand meters. At this altitude, cirrus clouds are made up of tiny ice crystals. Sunlight, falling at a certain angle on these crystals, is decomposed into a spectrum and reflected into the atmosphere. An inverted rainbow is much brighter than a normal rainbow, and the colors are reversed from purple to red. But as soon as the order of the crystals is broken, the colorful effect disappears, and the “smile in the sky” dissolves.

Double Rainbow

We already know that a rainbow in the sky appears from the fact that the rays of the sun penetrate through raindrops, refract and reflect on the other side of the sky in a multi-colored arc. And sometimes a sunbeam can build two, three, or even four rainbows in the sky at once. A double rainbow is obtained when a light beam reflects off the inner surface of raindrops twice. The first rainbow, the inner one, is always brighter than the second, the outer one, and the colors of the arcs on the second rainbow are mirrored and less bright. The sky between rainbows is always darker than the rest of the sky. The area of ​​sky between two rainbows is called Alexander's strip. Seeing a double rainbow is a good omen - this is good luck, wish fulfillment. So if you were lucky enough to see a double rainbow, like me, then hurry up to make a wish, and it will certainly come true.

winter rainbow

The most amazing thing is the rainbow in winter! This is very strange and unusual. Frost crackles, and suddenly a rainbow appears in the pale blue sky. A winter rainbow can only be seen in winter, during a severe frost, when the cold Sun shines in a pale blue sky, and the air is filled with small ice crystals. The sun's rays are refracted, passing through these crystals, as if through a prism and are reflected in the cold sky in a multi-colored arc. The ray of the sun passes through these crystals, is refracted, as in a prism, and is reflected in the sky with a beautiful rainbow.

ring rainbow

As I explained above, the rainbow itself is round. But we see only part of it in the form of an arc. But under certain circumstances, you can see an annular rainbow. This is only possible from a great height, for example, from an airplane.

Circumhorizontal or fiery rainbow

Circumhorizontal or fiery rainbow - formed when sunlight passes through light cirrus clouds and occurs only when the sun is very high in the sky. It turns out that the mysterious heavenly "fire" is born from ice! After all, cirrus clouds are located very high above the earth, where it is very cold at any time of the year, and therefore they consist of flat ice crystals! The sun's rays, passing through the vertical faces of the ice crystal, are refracted and ignite a fiery rainbow or a rounded-horizontal arc, as a fiery rainbow is called in science. A fiery rainbow is a relatively rare and unique phenomenon.

Red

The red rainbow appears in the sky only at sunset and is the last chord of the common rainbow. Sometimes it is extremely bright and remains visible even 5-10 minutes after sunset. At sunset, the rays travel a longer path through the air, and since the refractive index of water for longer wavelength (red) light is less than for short wavelength (violet), red light is less deflected by refraction. As the Sun descends below the horizon, the rainbow first loses the shortest purple waves, they dissipate immediately. Then blue, blue, green and yellow waves disappear. It remains the most persistent - the red arc.

3. Practical part

3.1 Own research.

Rainbow experiments at home

I conducted several experiments on obtaining a rainbow with an artificial light source:

Experience #1: getting a rainbow at home using a CD.

Equipment: CD, light source - flashlight.

I took the CD and "caught" the light from the flashlight with it, directed it at the wall. Got a rainbow. (Appendix No. 1, photos No. 1,2)

Experience #2: getting a rainbow at home with a mirror, water and a flashlight.

Experience progress:

Filled a glass container with water;

She put a tilted mirror in the water;

She directed the light of the flashlight to the part of the mirror immersed in water;

As a result of the refraction of the beam in the water and its reflection from the mirror, a rainbow appeared on the cabinet door (Appendix No. 1, photos No. 3,4).

Experience #3 : Get a rainbow at home with a glass prism and a flashlight. The experience of the decomposition of light into a spectrum, when a white beam of light passes through a prism.

To do this, I took a glass keychain, directed a white beam of light from a flashlight at it, and got an image of a rainbow on the wall. The light, which seemed white, played on the wall with all the colors of the rainbow. These seven-color, bright rainbow stripes are called the solar spectrum. So I repeated Newton's experiment, but only with an artificial light source . (Appendix No. 1, photos No. 5,6)

Conclusion : You can get a rainbow at home even with an artificial light source.

Experience number 4: obtaining white color, due to the merging of the seven colors of the spectrum, using a seven-color disk and a drill.

If light consists of seven colors, then seven colors should give white. I divided the white circle into 7 parts and colored it in the colors of the rainbow. My brother and I fixed a multi-colored circle on a drill. Turning on the drill, we saw that during rotation, the multi-colored disk changed color and turned white (Appendix No. 1, photos No. 7,8,9).

Conclusion: Light is made up of seven colors.

Experience number 5: getting a rainbow with soap bubbles.

I prepared a soap solution and blew a soap bubble. A rainbow appeared on the bubble. Light, passing through a soap bubble, is refracted and breaks up into colors, as a result a rainbow appears. A soap bubble is a prism. (Appendix No. 1, photos No. 10,11)

Experience number 6: getting a rainbow on a sunny day with a hose filled with water.

If the sun is shining brightly, there is another surefire way to make a rainbow. But for him, you have to go outside and take a hose and connect it to a water tap. Now it remains to pinch the end of the hose so that the water is finely sprayed when it exits the hose hole, and direct it upwards into the sun. In the splashes of water we will see a rainbow. A rainbow can be seen near waterfalls, fountains, against the backdrop of a curtain of drops sprayed by a watering machine or a field irrigation system. (Appendix No. 1, photo No. 12).

findings

While working on the topic: “How does a rainbow appear?”, I achieved the goal of my research work. Now I know the reason for the appearance of a rainbow and was able to create a rainbow at home. The hypothesis put forward that the rainbow appears in nature only on a sunny and rainy day, turned out to be wrong. I found out that a rainbow can appear on a moonlit night (without sun), during fog (without rain), without rain on a sunny day (inverted and fiery rainbows), and also in winter (without rain) during frost. Of course, the appearance of a rainbow on a sunny and rainy day happens most often, but not only. I found out what is the connection between rain, sun and the appearance of a rainbow. I think that I helped unravel the mystery of the sunbeam and gave an explanation of the rainbow as a natural phenomenon. By experience, I proved that the rainbow effect can be obtained at home and at any time of the year. All assigned tasks have been completed. Now I know when a rainbow appears and how it is formed. When you want to admire the rainbow, I hope that now you can get a rainbow at home. The rainbow is an amazing phenomenon of nature, one might say a miracle of nature that will never cease to amaze us.

5. References

1. I.K. Belkin "What is a rainbow?", Kvant. - 1984 - No. 12.

2. V.L. Bulat "Optical phenomena in nature" - M .: Education, 1974.

3. A. Bragin "About everything in the world." Series: Great children's encyclopedia.

4. Ya.E. Geguzin "Who creates a rainbow?" - Quantum, 1988

5. V.V. Mayer, R. V. Mayer "Artificial Rainbow". Quantum 1988 - No. 6.

6. “What is it? Who it?" - children's encyclopedia, comp. V. S. Shergin, A. I. Yuriev. - M.: AST, 2007.

7. E. Permyak "Magic Rainbow", 2008 Izd.Eksmo

8. Internet sources.

Application No. 1

Experience #1

Photo #1 Photo #2

Experience #2

Photo #4

Photo #3

Experience #3

Photo #5 Photo #6

Experience No. 4

Photo #7 Photo #8 Photo #9

Experience No. 5

Photo #10 Photo #11

Experience No. 6

The sun. Rain. Rainbow.

Scientists of different times tried to explain the thread, this is a natural phenomenon. The full theory of ra-du-gi you-ho-dit is beyond the geo-met-ri-che-sky and yes, the wave-new-howl op-ti-ki and tre-bu-et power -no-go ma-te-ma-ti-che-go-ap-pa-ra-ta. In the film, the first idea is given about ra-du-ge, someone, nevertheless, for-me-cha-tel-but also from- not so easy. This is a representation of os-no-va-but on the works of Rene De-kar-ta and Isa-a-ka New-to-on.

Rene Descartes explained the geo-metry of ra-du-gi: its shape and race in the sky. Isa-ak Newton "ras-kra-sil" ra-du-gu, giving an explanation of its non-color-there.

Great Isa-ak Newton in his know-me-no-that experience with a glass prize-mine, without someone-ro-go now it’s not about -dyat-sya lessons of physics, de-lo-lived white solar-nech-ny light into color-compositions-la-u-schi and pro-de-mon-stri-ro -shaft, that different colors correspond to different-personal-for-there-for-the-break-le-tion. This is a manifestation of na-zy-va-et-sya dis-per-si-her light. Namely, but bla-go-da-rya dis-per-si ra-du-ha different-but-color-naya.

Ras-look-rim now all the same drops of rain. What kind of drops participate in the for-mi-ro-va-nii of dan-no-go color ra-du-gi? From what has been said above, it follows that, for example, the violet-le-th-th-th-th color is formed by those and only those drops, some-rye lie on my straight line, about-ra-zu-yu-schey with the arrival of the sun-nech-ny-mi lu-cha-mi angle $ 42 ^(\circ)$. It means that the violet-le-th-th color of ra-du-gi lies on top-no-sti ko-well-sa with the top in blue-da-te-le, axis, yav-la-yu-shche-sya continues from-cut “The sun is an eye on-blu-da-te-la”, and the angle of dis- ra $42^(\circ)$. The rest of the colors also lie on the tops of the ko-well-owls with the same axis and corresponding to these colors-there are the corners of the races your-ra.

If the observer is looking at the ra-du-gu, then the Sun is on-ho-did-sya behind him. They say that the ra-du-ha is on-ho-dit-sya in the "pro-ti-in-sun-nech-noy point." You-so-ra-du-gi for-wee-sit from the location of the Sun. The most-may-shay ra-du-ha is better-cha-et-sya, when the Sun is close to the mountain-ri-zon-tu.

Let's now look at the rays of the Sun, pa-da-yu-shche on the lower part of the drop. In the si-lu of sym-metries for them, it is possible, but almost completely, to repeat the pro-ve-day-noe above race-judgment. One-on-one then, the beams on you-ho-de from the drops go up, and the observer from the Earth simply does not see them. But perhaps another pro-go-de-ni beam of light drop by drop! Rays can drop twice from the back wall of the drop and then get out of it.

Such a pro-ho-de-ni-beam-whose gives a second ra-du-gu. The second-ra-du-ga view at an angle of approximately $ 52 ^ (\circ) $ to the right-le-tion “The sun is an eye on the blu-da-te-la ". In such a way, she is higher than the first. Since the rays from-ra-zha-lied from the walls of the drops two times, in a row of colors in it, the reverse is red from the bottom , and fio-le-to-vy from above-hu.

With each ot-ra-same-nii, the intensity of the light is weakened-la-et-sya, so the second-ra-du-ha is less bright than first. Theo-re-ti-che-ski su-shche-stvu-yut and third ra-du-ga, and ra-du-gi are more than you-so-of-rows, but they don’t look -us under normal conditions, as-ku-lu-cha-yut-sya with many from-ra-same-no-yah in a drop.

Attention-ma-tel-ny man-lo-age for-me-tit the dark region of the sky, ras-lo-female between the first and second swarm ra-du-ga- mi. The fact is that after the interaction with the drops of rain, only a small number of rays come to the -blue-da-te-lu at an angle-la-mi from $41^(\circ)$ to $52^(\circ)$. Another not-always-for-me-cha-e-my sign of ra-du-gi - light-lo-dark-nye-lo-sy immediately under fio-le-to-howl doo-goy first howl ra-du-gi. However, their explanation of not-you-go-dit is beyond the framework of the geo-met-ri-che-sky op-ti-ki.

It is impossible to see in the sky a full circle of ra-du-gi hundred-I-sche-mu on Earth on-blue-yes-te-lyu. A full ra-du-gu - the circumference is whole, you can see it in the splashes of the background-ta-na, the races-lo-women-nee-so-co over the earth -lay. And in the sky you can see a full ra-du-gu from sa-mo-le-ta.

I. Newton. Op-ti-ka, or Trak-tat about from-ra-same-ni-yah, pre-lom-le-ni-yah, from-gi-ba-ni-yah and colors of light / Pe- re-waters from the third an-gli-sko-go from-da-nia 1721 with the ad-me-cha-ni-i-mi S. I. Wa-vi-lo-va. - From the second edition / Reviewed by G. S. Land-sber-gom. - M .: GITTL, 1954. - (Class-si-ki of nature-knowledge. Ma-te-ma-ti-ka, me-ha-ni-ka, physic-ka, ast-ro-no -mia.)

V. I. Ar-nold. Ra-du-ga // V. I. Ar-nold. Ma-te-ma-ti-che-no-ma-nie nature. - M.: MTsNMO, 2010.

H. Nus-sen-zweig. Theory of ra-du-gi // Successes in physical sciences. 1989. V. 125. S. 527-547.