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People have been asking this question for a long time. In some African myths, the rainbow is a snake that encircles the earth in a ring. But now we know that a rainbow is an optical phenomenon - the result of the refraction of light rays in water droplets during rain. But why do we see the rainbow in the form of an arc, and not, for example, in the form of a vertical colored stripe?

The shape of a rainbow is determined by the shape of the water droplets in which sunlight is refracted. And water droplets are more or less spherical (round. Passing through the drop and refracting in it, a beam of white sunlight is converted into a series of colored funnels inserted one into the other, facing the observer. The outer funnel is red, orange, yellow is inserted into it, further goes green, etc., ending with an inner violet, so that each individual drop forms a whole rainbow.
Of course, the rainbow from one drop is weak, and in nature it is impossible to see it separately, since there are many drops in the curtain of rain. The rainbow that we see in the sky is formed by myriads of drops. Each drop creates a series of colored funnels (or cones) nested one inside the other. But only one colored ray enters the rainbow from a single drop. The observer's eye is a common point at which the colored rays from many drops intersect. drops, but at the same angle and falling into the eye of the observer, form a red arc of the rainbow.All orange and other colored rays also form arcs. Therefore, the rainbow is round.

We are accustomed to seeing the rainbow as an arc. In fact, this arc is only part of a multi-colored circle. In its entirety, this natural phenomenon can only be observed at high altitude, for example, from an airplane.

When the last raindrops fall on the ground, and a rainbow appears in the sky, you, looking at it, think: why is this happening? Where does a beautiful arc of multi-colored stripes come from in the sky? The science of physics, which has already given you answers to many difficult questions more than once, will help answer this question.

The rainbow is an extraordinary phenomenon of nature. And although we see her quite often, every time we rejoice at her appearance and beauty. The rainbow appears as soon as the cloud begins to leave, and the sun takes its place in the sky. It turns out that for some time the rain is visible to people as if “from the outside”. The rays of the sun illuminate the rain cloud and, passing through the raindrops, change their color. The fact is that the sun's rays are not at all white and the same, as it seems to us. All of them have different lengths, and each length has its own "color". That's why the rainbow looks so colorful to us.

But the color of the rainbow is bright, and sometimes barely noticeable. And it depends on the size of the raindrops. If the drops are large, the colors of the rainbow will be bright. If small, the celestial arc will be poorly visible. In the past, people could not explain the appearance of a rainbow. And it was difficult to find a person who would remain indifferent to her. Because there are so many legends and beliefs associated with the rainbow. The ancient Slavs, looking at the rainbow, predicted the weather. If the rainbow was low and wide, the people expected bad weather. And high and narrow - promised good weather.

In England, it is considered a good omen to see a rainbow and immediately make a wish. And in Ireland today they believe that in the place where the rainbow sticks to the ground, there is a treasure with gold. Of course, you are a fairly reasonable person, and you do not believe in golden treasures. And you understand that it is impossible to get to where the rainbow touches the ground.

Are you wondering why we only see part of the rainbow? Let's talk about it. You probably already noticed that you cannot observe both the sun and the rainbow at the same time. After all, a rainbow is a reflection of the sun's rays. Only part of the celestial arc is visible from the earth. But the higher a person rises, for example, up a mountain, the more the rainbow will look like a circle. And from the window of an airplane, you will someday be able to see a round rainbow!

Why is the rainbow semicircular? People have been asking this question for a long time. In some African myths, a rainbow is a snake that encircles the Earth in a ring. But now we know that a rainbow is the result of the refraction of light rays in water droplets during rain. But why do we see the rainbow in the form of an arc, and not, for example, in the form of a vertical colored stripe?

Two people standing side by side see each their own rainbow! Because at every moment the rainbow is formed by the refraction of the sun's rays in new and new drops. Raindrops are falling. The place of the fallen drop is occupied by another and manages to send its colored rays to the rainbow, followed by the next one, and so on.

The type of rainbow - the width of the arcs, the presence, location and brightness of individual color tones, the position of additional arcs - is very dependent on the size of the raindrops. The larger the raindrops, the narrower and brighter the rainbow is. Characteristic of large drops is the presence of saturated red color in the main rainbow. Numerous additional arcs also have bright colors and directly, without gaps, adjoin the main rainbows. The smaller the droplets, the wider and faded the rainbow with an orange or yellow edge. Additional arcs are further apart both from each other and from the main rainbows. Thus, by the appearance of the rainbow, one can approximately estimate the size of the raindrops that formed this rainbow.

The type of rainbow also depends on the shape of the drops. When falling in the air, large drops are flattened and lose their sphericity. The stronger the flattening of the droplets, the smaller the radius of the rainbow they form.

A celestial rainbow is a beautiful and at the same time complex physical phenomenon that can be observed after rain or during fog if the sun is shining. A lot of ancient beliefs and myths among different peoples are associated with the rainbow, and in Russia in the old days the weather was predicted from it. A narrow and high rainbow foreshadowed good weather, and a wide and low one foreshadowed bad weather.

A rainbow is a meteorological phenomenon that occurs in the sky. This is a huge arc, consisting of different colors. Rainbows are caused by high moisture content in the air, which usually occurs after rain or fog. The multi-colored arc appears due to the refraction of sunlight in water droplets, which are contained in the atmosphere in the form of vapor. Droplets refract light differently depending on the wavelength of the light. For example, red has the longest wavelengths, so this color crowns the color spectrum of the rainbow, it belongs to the widest arc. Then the red color in the spectrum smoothly turns into orange, then into yellow, etc. The weakest in terms of resistance to deflection during refraction in water is purple, its waves are the shortest, so the observer sees that this color belongs to the shortest arc of the rainbow - the inner . The method of breaking down white sunlight into a color spectrum is called "dispersion". With dispersion, the refractive index of light depends on the wavelength of the light wave. In optics, the phenomenon of a rainbow is called "caustics". A caustic is a light curve line of various shapes, in this case a semicircle or an arc. The multi-colored rays that make up the rainbow run parallel to each other, not converging, so you can observe the color transition inherent in it throughout the rainbow. From childhood, everyone knows rhymes and sayings that help remember the colors of the rainbow. For example, every schoolchild knows the saying “every hunter wants to know where the pheasant is sitting”. However, in fact, the color spectrum of the rainbow does not consist of seven colors, there are many more. Primary colors pass into each other through a large number of shades and intermediate colors. It should be added that a person can observe the phenomenon of a rainbow only in the course of sunlight. It is impossible to see the rainbow and the luminary at the same time, the sun always remains behind. Moreover, the higher the observer is (on a hill or in an airplane), the more the visible shape of the rainbow approaches a circle.

Why is the rainbow round and the dome of the sky. WHY DOES A RAINBOW HAVE ARC SHAPE?

Why is the rainbow semicircular? People have been asking this question for a long time. In some African myths, a rainbow is a snake that encircles the Earth in a ring. But now we know that a rainbow is an optical phenomenon - the result of the refraction of light rays in water droplets during rain. But why do we see the rainbow in the form of an arc, and not, for example, in the form of a vertical colored stripe?

The shape of a rainbow is determined by the shape of the water droplets in which sunlight is refracted. And water droplets are more or less spherical (round). Passing through the drop and being refracted in it, a beam of white sunlight is transformed into a series of colored funnels inserted one into the other, facing the observer. The outer funnel is red, orange is inserted into it, yellow, then comes green, etc., ending with the inner violet. Thus, each individual drop forms a whole rainbow.

Of course, the rainbow from one drop is weak, and in nature it is impossible to see it separately, since there are many drops in the curtain of rain. The rainbow that we see in the sky is formed by myriads of drops. Each drop creates a series of nested colored funnels (or cones). But from a single drop, only one colored ray enters the rainbow. The observer's eye is a common point at which colored rays from many drops intersect. For example, all the red rays that come out of different drops, but at the same angle and hit the observer's eye, form a red arc of the rainbow. All orange and other colored rays also form arcs. Therefore, the rainbow is round.

We are accustomed to seeing the rainbow as an arc. In fact, this arc is only part of a multi-colored circle. In its entirety, this natural phenomenon can only be observed at high altitude, for example, from an airplane.

There is such a group of optical phenomena, which is called a halo. They are caused by the refraction of light rays by tiny ice crystals in cirrus clouds and mists. Most often, halos form around the Sun or Moon. Here is an example of such a phenomenon - a spherical rainbow around the Sun:

A rainbow is an atmospheric phenomenon. She appears in the sky before or after rain, she can be seen near a waterfall or above the spray at a fountain. It looks different - it can be an arc, sometimes in the form of a circle or splashes. In order for a rainbow to appear after the rain, sunlight is needed.

Imagine that the rainbow is one ray of sunshine. Usually the sun's rays are invisible, as they are scattered by air. Daytime sunlight is often referred to as white. In fact, the sensation of white light is caused by mixing colors such as red, orange, yellow, green, cyan, indigo and violet. This combination of colors is called the solar spectrum, and their combination gives white.
Green foliage, blue sky, bright colors of nature - this is all the refraction of the sun's rays, which, passing through a thin layer of the atmosphere, reflect the constituent parts of the white color.
The concept of the spectral composition of white was introduced by Isaac Newton. He conducted an experiment when a beam from a light source was passed through a narrow slit, behind which a lens was placed. From it, a beam of light was redirected to a prism, where it was refracted and disintegrated into components.
Remember that a prism is a polyhedron with a base, the sides of which form a three-dimensional figure. A drop of water is a real prism. Getting through it, the ray of the sun is refracted and turns into a rainbow.
Sunlight is split in different ways, because each wavelength of the spectrum has its own length. A distinctive feature is the fact that two nearby observers will each see their own rainbow.
The effect will occur due to the fact that the drops cannot be the same, and the arrangement of colors, their brightness, the width of the rainbow arcs directly depend on the size and shape of the drops.
If you want to see the rainbow in all its glory, you need the sun to shine on your back. The rainbow will be brighter and more saturated if the light is refracted through large drops, if they are small, the arcs will be wider, but their color will be less bright. It happens that when falling raindrops become flattened, in this case the radius of the rainbow will be small. If the drops stretch when falling, then the rainbow will be high, but its colors are pale.

The rainbow is one of the most amazing natural phenomena. People have been thinking about the essence of this phenomenon for a long time. The rainbow is the companion of rain. The time of its appearance depends on the movement of the cloud that gives showers. A rainbow can occur both before the rain, and in the process of precipitation, or at the end of the process.

What is a rainbow?
A rainbow is usually a colored arc with an angular radius of 42°. The arc is visible against the background of a rain curtain or rainfall bands that do not always reach the ground. A rainbow is observed in that side of the sky, which is opposite to the sun, while the sun is not covered by clouds. Most often, such conditions are created in the summer, during the so-called "mushroom" rains. The center of the rainbow is the antisolar point - this point is diametrically opposite to the Sun. Seven colors are distinguished in the rainbow, in addition, the rainbow can be seen near a fountain or waterfall, against the backdrop of a curtain of drops from an irrigation system.

Where does the amazing colorful light coming from the rainbow come from? The source of a rainbow is the sunlight decomposed into its components. This light travels across the firmament in such a way that it appears to come from that part of the firmament which is opposite to the sun. The main features of the rainbow are correctly explained by the Descartes-Newton theory created more than 300 years ago.

An object capable of splitting a beam of light into its components is called a "prism". If we talk about the rainbow, then the role of the "prism" is played by raindrops. A rainbow is a large curved spectrum or a strip of colored lines formed as a result of the decomposition of a beam of light passing through raindrops. The colors go in the following order, if you count from the outer radius to the inner one (it’s quite easy to remember this spectrum by learning a simple acrostic phrase: “Every hunter wants to know where the pheasant sits”, here the first letter of each word corresponds to the first letter of the color):

One is Red;

Hunter - Orange;

Desires - Yellow;

Know - Green;

Where - Blue;

Sitting - Blue;

Pheasant - Purple.

A rainbow can be seen at a time when the Sun is shining in parallel with the shower. To see it, you need to be strictly between the Sun and the rain. In this case, the Sun should be behind, and the rain should be in front.

Quick answer: There are 7 colors in the rainbow.

What is a rainbow? This is an optical phenomenon that can be observed when the Sun (and in some cases the Moon) illuminates a large number of water droplets (we are talking about fog or water). The rainbow is a circle in the form of an arc, which has seven colors of the spectrum: blue, purple, green, cyan, orange, yellow and red. It is worth noting that the Sun at the moment of observing the rainbow is always behind the observer, so it is impossible to see both of them at the same time, except with the help of special equipment.

Where does this optical phenomenon come from? It occurs as a result of the refraction of light in water droplets that float in the atmosphere. Droplets have the ability to deflect light of different colors differently. White color decomposes into a spectrum, resulting in light dispersion - refraction of a substance, depending on the frequency or phase velocity of light. Roughly speaking, the sun's color passes through the smallest droplets of water, refracts and is visible to the human eye as several colors at once.

There are two types of rainbow - primary and secondary. In the first case, the light inside the drop is reflected only once, the shades in this case are quite bright. In the second case, the light is reflected twice and the colors that our eyes take on are no longer so bright. There is also a rainbow of the third, and even the fourth order, but no one has observed this miracle of nature with their own eyes for several centuries now.

It is worth noting that the colors in the rainbow are arranged in the sequence that corresponds to the spectrum of visible light. To remember them, in some countries they even came up with such rhymes and phrases. Russia is no exception. In our country, several phrases are used at once, here they are:

Once Jacques the bell ringer broke a lantern with his head.

Every hunter wants to know where the pheasant is sitting.

Mole sheep, giraffe, hare sewed blue jerseys.

Every designer wants to know where to download photoshop.

Who feels the cruel ringing of the gong of resistance to fatality?

The quark is surrounded by a hot curtain of gluons that create fluids.

It is easy to guess that the initial letter of each word denotes the initial letter of the color:

Like red.

Once - orange.

Jack is yellow.

Ringer - green.

The head is blue.

Broke - blue.

Lantern - purple.

A rainbow is an amazing and incredibly beautiful meteorological and optical natural phenomenon. It can be observed mainly after the rain, when the sun comes out. It is this that is the reason that we can see this wonderful phenomenon in the sky, as well as distinguish the colors of the rainbow, arranged in order.

Causes

A rainbow appears due to the fact that light coming from the sun or from another source is refracted in water droplets that slowly fall to the ground. With their help, white light "breaks", forming the colors of the rainbow. They are arranged in order due to different degrees of light deflection (for example, red light is deflected by fewer degrees than violet). Moreover, a rainbow can also appear due to moonlight, but it is very difficult for our eyes to distinguish it in low light. When forming a circle, which is formed by the "celestial bridge", the center is always on a straight line passing through the Sun or the Moon. For those who observe this phenomenon from the ground, this "bridge" appears as an arc. But the higher the viewpoint, the fuller the rainbow is seen. If you observe it from a mountain or from the air, it can appear before your eyes in the form of a whole circle.

The order of the colors of the rainbow

Many people know a phrase that allows you to remember the order in which the colors of the rainbow are located. For those who don’t know or don’t remember, let’s recall how this line sounds: “Every Hunter Wants to Know Where the Pheasant Sits” (by the way, now there are many analogues of this famous monostikha, more modern, and sometimes very funny). The colors of the rainbow, in order, are red, orange, yellow, green, blue, indigo, and violet.

These colors do not change their location, imprinting in memory the eternal view of such an incredibly beautiful phenomenon. The rainbow we often see is the primary one. During its formation, white light undergoes only one internal reflection. In this case, the red light is outside, as we are used to seeing. However, a secondary rainbow can also form. This is a rather rare phenomenon in which white light is reflected twice in the droplets. In this case, the colors of the rainbow are already in order in the opposite direction (from purple to red). In this case, the part of the sky that is between these two arcs becomes darker. In places with very clean air, you can even observe a "triple" rainbow.

Fancy rainbows

In addition to the familiar arc-shaped rainbow, you can observe its other forms. For example, one can observe lunar rainbows (but it is difficult for the human eye to catch them, for this the glow from the moon must be very bright), foggy, annular (these phenomena have already been mentioned above) and even inverted. In addition, the rainbow can be observed in winter. At this time of the year, it sometimes occurs due to severe frosts. But some of these phenomena have nothing to do with "heavenly bridges". Very often mistaken for a rainbow (this is the name of a luminous ring that forms around a certain object).

A rainbow will make anyone smile! Especially large, stretching to the whole sky. Or a small one, nestled in a table fountain - so its own, tame. What determines what size the rainbow will grow, and what is it all about? Read the tooltips on the diagram to find out.

1. A rainbow is an optical illusion. It occurs when water droplets (rain, fog or spray from a waterfall) are illuminated by the sun. There are also lunar rainbows (one of them is in the photo), they can be observed at night.

2. Getting into the droplet, the light is refracted twice at the boundary of air and water and reflected from the “rear” wall of the droplet, returning at an angle of approximately 42 degrees to the light. The refractive index of light with different wavelengths is slightly different, so rays of different colors come out of the droplet at different angles. So white light turns into a rainbow.

3. The illusion of a rainbow is created by those drops that appear at the intersection of the sun's rays and the line of sight of the observer. All rainbows in the world have the same angular size - 42 degrees.

4. The linear radius of the rainbow depends on the distance between the observer and the water drops. For example, a rainbow that appears at a distance of 5 meters from a person will have a radius of approximately 4.5 meters (5 meters times the tangent of 42°).

5. The center of the rainbow is located at the antisolar point - on the straight line connecting the observer and the sun. The plane of the rainbow is perpendicular to this line. The antisolar point is imaginary and may be underground. By the way, on a clear day, the luminary is able to create not only illusory, but also quite tangible effects, for example.

Children believe that a rainbow is a tangible object. For example, a road along which you can climb to the clouds. Later, childhood dreams are shattered by boring science, it turns out that neither touching the rainbow nor walking on it will work. But you can measure its size!

We continue the series of publications prepared by the interactive popular science blog "I'll explain in two minutes". The blog talks about simple and complex things that surround us every day and do not raise any questions exactly as long as we do not think about them. For example, there you can find out how long it takes to fly to Mars and what dates to take tickets for.

1. Rainbow is an optical illusion. It occurs when water droplets (rain, fog or spray from a waterfall) are illuminated by the sun. There are also lunar rainbows (one of them is in the photo), they can be observed at night.

2. Getting into the droplet, the light is refracted twice at the air-water interface and reflected from the "rear" wall of the droplet, returning at an angle of about 42 degrees to the light. The refractive index of light with different wavelengths is slightly different, so rays of different colors come out of the droplet at different angles. So white light turns into a rainbow.

The general physical picture of the rainbow has already been clearly described. Mark Antony de Dominis(1611). On the basis of experimental observations, he came to the conclusion that a rainbow is obtained as a result of reflection from the inner surface of a rain drop and double refraction - at the entrance to the drop and at the exit from it.

Rene Descartes gave a fuller explanation of the rainbow in his work "Meteors" in the chapter "On the Rainbow" (1635)

Isaac Newton in the treatise "Optics or Treatise on reflections, refractions, bendings and colors of light" supplemented the theory of the rainbow in relation to the colors of the rainbow and explained the mechanism for the formation of a secondary rainbow.

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. J.B. Erie(1836) and J.M. Pernter (1897).

Newton called the system of colors of a decayed sunbeam spectrum- from lat. spectrum - representation, vision, ghost.

Newton distinguished 7 colors in the rainbow.
The multi-color spectrum of the rainbow is continuous!)

Why are the colors of the rainbow arranged in a strict sequence??
Each colored beam has its own break angle. Violet, which occupies the lowest position in the spectrum, has the smallest angle.

Each of us sees our own "personal" rainbow.
When you look at a rainbow, you see the light refracted from some raindrops, and the person standing next to you looks at the same rainbow and sees the light reflected from other raindrops.

The center of the circle described by the rainbow, lies on a straight line passing through the observer and the Sun, and the Sun is always behind the observer.

What is the radius of the rainbow?
A rainbow is an optical effect resulting from the refraction of sunlight in drops of atmospheric moisture.
These drops can be located at different distances from us. It is calculated that the height of the rainbow is approximately 0.9 of the distance from the observer's eye. Since we see the rainbow as a semicircle, this value can be considered the radius of an imaginary circle into which the rainbow could be closed.

Does a rainbow have a beginning and an end?
Under ideal conditions, in an airplane flight or from a high mountain, you can see the rainbow as a closed curve that surrounds a point diametrically opposite the Sun.

As the sun rises higher 42 degrees above the horizon, the rainbow is not visible from the surface of the Earth.

rainbow brightness depends on the amount of raindrops. If they are large (1-2 mm in diameter) - the rainbow is very bright.

Double Rainbow
This is explained by the fact that the sun's rays are reflected twice in drops that are above the drops that form an ordinary rainbow. In this case, the upper rainbow is always less bright than the main one, and the colors in it are arranged in reverse order.
Less common is a triple and even a rainbow of four arcs!
In this case, additional rainbows are located only above the central part of the main rainbows and disappear when the latter move to a vertical position.

The distance between two rainbows is called Alexander's dark streak. It is named after the ancient Greek philosopher Alexander of Aphrodisias, who first described this phenomenon in 200 BC. AD

Night Rainbow - Moon Rainbow
A lunar rainbow is a rare refraction of moonlight. We see this rainbow as white, even though all colors are present.

fiery rainbow- one of the varieties of "halo" - an optical effect in the form of a luminous ring around the sun, which mainly appears in the region of cirrus clouds: small pieces of ice reflect the incident light and "ignite" the clouds, painting them in different colors.

The rainbow is one of the few natural phenomena that man has learned to reproduce.
artificial rainbows can be seen next to waterfalls and fountains. They appear against the background of the smallest droplets sprayed by the installation.

Calculations according to the formulas of the diffraction theory, performed for drops of different

size, showed that the whole view of the rainbow - the width of the arcs, the presence, location and

the brightness of individual color tones, the position of additional arcs is very strong

depends on the size of the raindrops. Here are the main characteristics of the external

rainbow type for droplets of different radii.

Drop radius 0.5-1 mm. The outer edge of the main rainbow is bright,

dark red, followed by light red, and then all the colors of the rainbow alternate.

Violet and green seem especially bright. There are many additional arcs (up to

five), they alternate violet-pink tones with green. Additional arcs

directly adjacent to the main rainbows.

Drop radius 0.25 mm. The red faucet of the rainbow has become weaker. Other colors

are still visible. Several purple-pink additional arcs are replaced

green.

Drop radius 0.10-0.15 mm. There is no more red in the main rainbow.

The outer edge of the rainbow is orange. The rest of the rainbow is well developed.

Additional arcs become increasingly yellow. Between them and between the main

rainbow and the first additional gaps appeared.

Drop radius 0.04-0.05 mm. The rainbow has become noticeably wider and paler, Outer

its edge is pale yellow. The brightest color is purple. First

the additional arc is separated from the main rainbow by a fairly wide gap,

its color is whitish, slightly greenish and whitish-violet.

Drop radius 0.03 mm. The main rainbow is even wider with very faint

slightly yellowish edge, contains separate white stripes.

Drop radius 0.025 mm or less. The rainbow is completely white. She is about

twice as wide as a regular rainbow and has the appearance of a shiny white stripe. Inside her

there may be additional colored arcs, initially pale blue or green,

then whitish red.

Thus, by the appearance of the rainbow, one can approximately estimate the size of raindrops,

that formed this rainbow. In general, the larger the raindrops, the better the rainbow.

turns out narrower and brighter, especially characteristic of large drops is

the presence of saturated red in the main rainbow. Numerous

additional arcs also have bright colors and directly, without

gaps adjacent to the main rainbows. The smaller the drops, the rainbow

becomes wider and faded with an orange or yellow edge.

The type of rainbow also depends on the shape of the drops. When falling in the air, large drops

flatten, lose their sphericity. The vertical section of such drops

approaching an ellipse. Calculations showed that the minimum deviation of red

rays passing through flattened drops with a radius of 0.5 mm is 140°.

Therefore, the angular size of the red arc will not be 42°, but only 40°. For more

large drops, for example with a radius of 1.0 mm, the minimum deviation of the red

rays will be 149°, and the red arc of the rainbow will have a size of 31°, instead of

42°. Thus, the stronger the flattening of the droplets, the smaller the radius

the rainbow they form.

The "secret" of additional arcs has been solved!

A. Fraser, having simultaneously considered the influence of the size and shape of drops on the appearance

rainbow, managed to reveal the "secret" of the appearance of additional arcs. As soon as

it was said that the decrease in the size of the predominant droplets and the flattening of the large

act in opposite directions. What will prevail? When and what

will the influence prevail?

A clear illustration of the interaction of both factors and their joint influence

on the kind of rainbow are fig. 3 a and b compiled by A. Fraser,

based on calculations: These figures show the intensity distribution

light in the main rainbow and additional arcs, depending on the droplet size.

A complex undulating surface in the foreground (Fig. 3 a)

composed of many individual curves. Each curve gives a distribution

and the intensity of light in a rainbow from a single drop. Every fifth curve is drawn

thicker, the numbers on the right indicate the radius of the drop corresponding to the curve, in

millimeters. All curves start on the left with very low intensity (outside

rainbows), then quickly rise to a maximum between 138° and 139° (the first

rainbow). The next ridge on the right is the first additional arc, followed by the second

additional arc, etc. The distance between the arcs, as can be seen from the figure,

decreases rapidly with increasing droplet radius. This is the effect of the first factor.

The rainbow becomes narrower as the droplet size increases.

The upper curve S is the result of adding the contributions of droplets of all sizes.

It characterizes the distribution of light intensity in the final rainbow,

which we see.

137 138 139 140 141 142

Angular distance from the Sun

137 138 139 140 141 142

Angular distance from the Sun

Rice. 3. Distribution of light intensity in the main rainbow and additional

arcs depending on droplet size.

a - without taking into account the flattening of drops; b - taking into account the flattening of drops. S-

total curve.

In Fig.3 b the same curves are shown, but now the influence of flattening is taken into account

drops, the stronger, the larger the drops. Individual curves for large

flattened droplets are shifted towards larger minimum angles of deviation from

Sun (or, which is the same, in the direction of decreasing radii of rainbows), and as a result

the entire undulating surface turned out to be curved to the right (individual

the maxima have gone to the right). This led to the fact that on the resulting total

curve appeared, in addition to the main rainbow, additional arcs, on the corners

distances from the Sun: the first -140.5°, the second -141.3°, the third - 142.4°,

the fourth is 142.5°.

Additional arcs are visible only near the top of the main rainbow, as they

formed only by vertical or close to them rays that have passed through

elliptical sections of drops.

Calculations are shown, but this can also be seen in Fig. 3 b, what

additional, arcs are created mainly by drops ranging in size from 0.2 to 0.3 mm.

Larger and smaller drops give maxima that overlap each other.

friend and too far away from the main rainbow (they go to the right). rainbows

drops with a diameter of 0.2-0.3 mm are in a preferential position, since

their highs have not shifted anywhere. Thus, it can be concluded that

additional arcs are visible if in a heavy rain are present in significant,

the number of drops with a radius of 0.25 mm and few larger drops that lubricate

picture. Therefore, additional arcs are more often visible and the most colorful are not very bright.

intense summer rain showers. They also appear against the backdrop of a veil of

tiny droplets formed when water is sprayed into irrigation

installations.

Is it possible to see the whole circle of the rainbow? From the surface of the earth we can observe

a rainbow at best in the form of a half circle when the Sun is at

horizon. When the Sun rises, the rainbow goes below the horizon. The first rainbow can be

to see at heights of the Sun more than 42 °, and the second - more than 50 °. From an airplane, and

better from a helicopter (more view) you can watch the rainbow in the form of a whole circle!

The description of such a circular rainbow (it and the rainbow, that is, the arc, is already inconvenient

name!) was placed in the journal "Nature". She was seen by the passengers of the plane,

flying in the Novosibirsk region at an altitude of 1000 m.

Rainbow light polarization. The light of the rainbow is characterized by an unusually high

degree of polarization. In the first rainbow, it reaches 90%, in the second, about 80%. AT

This is easy to see if you look at the rainbow through a polarizing prism.

Nicholas. At small angles of rotation of the prism, the rainbow disappears completely.

Rainbow without rain?

Are there rainbows without rain, or without rain streaks? It turns out that there are

in the laboratory. Artificial rainbows were created by refraction

light in one suspended drop of distilled water, water with syrup, or

clear oil. Droplet sizes varied from 1.5 to 4.5 mm. heavy drops

stretched under the action of gravity, and their cross section in the vertical

plane was an ellipse. When the droplet is illuminated by a helium beam

neon laser (with a wavelength of 0.6328 μm), not only the first and

the second of the rainbow, but also the extraordinarily bright third and fourth, centered around

light source (in this case, a laser). Sometimes I even managed to get

fifth and sixth rainbows. These rainbows, like the first and second, the sheaf was aside,

opposite to the source.

So, one drop created so many rainbows! True, these rainbows were not

iridescent. All of them were of the same color, red, as they were formed not by white

light source, but a monochromatic red beam.

misty rainbow

In nature, there are white rainbows, which were mentioned above. They appear

when illuminated by the sun's rays, a faint fog consisting of droplets

with a radius of 0.025 mm or less. They are called foggy rainbows. In addition to the main

rainbows in the form of a brilliant white arc with a barely visible yellowish edge

sometimes colored additional arcs are observed: very weak blue or

green arc and then whitish red.

A similar-looking white rainbow can be seen when a spotlight beam

located behind you illuminates intense haze or light fog in front of you.

you. Even a street lamp can create, albeit a very faint, white rainbow,

visible against the dark background of the night sky.

moon rainbows

Like solar rainbows, lunar rainbows can also occur. They are weaker and

appear at full moon. Lunar rainbows are rarer than

sunny. For their occurrence, a combination of two conditions is necessary: complete

The moon not obscured by clouds and the fall of torrential rain or its streaks

(not reaching the Earth). Showers due to daytime convective

air movements, fall out much less often at night.

Lunar rainbows can be observed anywhere in the world where

the above two conditions.

Daytime, solar rainbows, even formed by the very small drops of rain

or fog, quite whitish, light, and yet their outer edge at least

weakly, but colored orange or yellow. Rainbows formed by the moon

rays, do not justify their name at all, since they are not iridescent and

look like light, completely white arcs.

The absence of red color in lunar rainbows even with large raindrops

rainfall is explained by the low level of lighting at night, in which completely

the sensitivity of the eye to red rays is lost. Other colored

the rays of the rainbow also lose much of their color tone due to

achromaticity (uncolored) human night vision.

Ministry of General and Vocational Education of the Russian Federation

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