How a rainbow appears. Start in Science What is a rainbow short definition

18.10.2019

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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 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 causes positive emotions cheers people up. 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 don't rainbows exist? 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."

AT Slavic myths and legends, the rainbow was considered a magical heavenly bridge thrown from heaven to earth, the 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 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 gave, also, 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, decomposition had not yet been discovered white light into the spectrum at refraction. 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. Spectrum

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 component 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, refracted, leaves the drop, and some part goes through a 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 in purple, and the outermost region is in 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 - top part 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 AND does W nat, G de FROM 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 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 They 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 in English language the next memo appeared - 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's in Japanese simply no. The Japanese, rewriting Chinese characters, lost the green character (in Chinese he is). The British will agree with the Japanese on the number of flowers, but not on the composition. The English do not have a language blue color. 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 an ordinary rainbow is most often observed. 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 from the Sun. less light than the sun shines during the day. The lunar rainbow is visible with a very bright night Sun - the Moon. At night, when high in the dark, necessarily dark, sky hangs a full, necessarily full, moon and at the same time opposite the moon it's raining may be lucky enough to see the 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. Winter rainbow can only be seen in winter, during hard 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 with high altitude, 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: receiving 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. 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 background of a curtain of drops sprayed by a watering machine or a field watering installation. (Appendix No. 1, photo No. 12).

conclusions

During my work on the topic: “How does a rainbow appear?”, I achieved my goal 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. Rainbow - amazing phenomenon nature, we can 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

People from time immemorial have tried to explain the nature of the rainbow. Inhabitants Ancient Russia they believed that the multi-colored stripes in the sky are a shining rocker, with the help of which Lada Perunitsa draws water from the sea-ocean, in order to then irrigate fields and fields with it. Another version was followed American Indians who were sure that the rainbow is a ladder leading to another world. Well, the harsh Scandinavians identified the celestial arc with a bridge on which the guardian of the gods Heimdall watches day and night.

AiF.ru tells how it explains the formation of this natural phenomenon modern science, and also shares the secrets of how to become the guardian of the rainbow yourself.

Why does a rainbow appear?

To understand why a rainbow appears, you need to remember what a ray of light is. From the course school physics it is known that it consists of particles flying with great speed - segments of an electromagnetic wave. Short and long waves differ in color, but all together in a single stream they are perceived by the human eye as white light.

And only when a beam of light "bumps" into a transparent barrier - a drop of water or glass - it breaks up into different colors.

The shortest red electromagnetic waves have the least energy, so they deflect less than others. The longest violet wavelengths, on the contrary, deviate more than others. In this way, most of colors of the rainbow is located between the red and purple lines.

The human eye distinguishes seven colors - red, orange, yellow, green, blue, indigo and violet. But it should be borne in mind that in fact the colors smoothly transition into each other through many intermediate shades.

The inside of a white rainbow can be slightly purple, and the outside a little orange.

How and where does a fiery rainbow appear?

Fire rainbow. Photo: www.globallookpress.com

The fiery rainbow mainly appears in the region of cirrus clouds: small pieces of ice reflect the incident light and literally “ignite” the clouds, painting them in different colors.

Can you see a rainbow at night?

Yes it is possible. The light of the moon, reflected by water particles from rain or a waterfall, forms a color spectrum that is indistinguishable to the eye at night and appears white due to the features human vision in poor lighting conditions. This rainbow is best seen during a full moon.

Lunar rainbow. Photo: Shutterstock.com / Muskoka Stock Photos

How to make a rainbow with your own hands?

You will need: glass, water, sheet of paper.

What to do:

1. Put a faceted glass filled with water to the window where the sun shines from.

2. Put a sheet of paper on the floor near the window so that light falls on it.

3. Moisten the window with hot water.

4. Change the position of the glass and sheet of paper until the rainbow is visible.

You will need: hose with water.

What to do:

1. Take a hose with running water and lightly pinch its “neck” so that splashes appear.

3. Look closely and see a rainbow in the splashes.

How to remember the colors of the rainbow?

There are special phrases that help you remember the sequence of colors in the rainbow. The first letter of each word corresponds to the first letter of the color of the rainbow stripe - red, orange, yellow, green, blue, indigo, violet.

Every hunter wants to know where the pheasant is sitting.

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

A mole to a sheep, a giraffe, a bunny stroked old jerseys.

Every designer wants to know where to download photoshop.

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

How to predict the weather from a rainbow?

If the spectrum of the rainbow is dominated by red, then you need to wait for a strong wind.

Rainy weather in the coming days will be if you see a double or triple rainbow.

A high rainbow indicates that the weather will be clear, and a low one indicates that it will be rainy.

If more Green colour- there will be rains, yellow - good weather, red - wind and drought.

A rainbow in winter is a rarity, it signals the impending frost or snow.

rainbow along the river heavy rain, and across - to clear weather.

The appearance of the rainbow on Saturday promises a rainy next week.

According to the Bible, the rainbow is a symbol of God's promise to mankind never again to arrange. Indeed, often a rainbow is evidence that it has rained somewhere nearby. As a rule, we see a rainbow in sunny weather, when there are rain clouds(usually cumulonimbus). To find out what a rainbow is, in this article we will talk about its two components: sunlight and raindrops.

Primary and secondary rainbows.

Why and where do rainbows appear?

Sunlight is a mixture of colors. When light rays pass through a glass prism, some of them are bent and refracted more than others. Light leaving a prism spreads out into a continuous band of colors called a spectrum. The colors go from red, which is the least curved, through orange, yellow, green, and blue all the way to purple. The purple color is curved the most.

Sunlight passing through water drops is refracted in the same way as sunlight passing through a prism. This creates an atmospheric solar spectrum in the sky, which we call a rainbow.

In short, a rainbow is a group of semi-circular arcs of color that appears as a huge arch in the sky. Rainbows are often seen after rain. They form when sunlight breaks through rain clouds. Raindrops act like miniature prisms, refracting or breaking sunlight into different colors and also reflecting it, creating a spectrum.

We can easily create an artificial rainbow at home with a garden hose. You just need to stand with your back to the sun and adjust the watering of the hose to a fine spray, thus creating water "dust". A rainbow can also be seen in front of the place where the spray of the waterfall falls.

Rainbow at Victoria Falls (on the border of Zambia and Zimbabwe)

If there is only one rainbow, or if it is the main one, then such a rainbow always has a red color outside (top) of the arc and blue with inside. Typically, the radius of a rainbow is about one quarter of the visible sky, or 42 degrees. When it is raining nearby, you need to look at that part of the sky that is opposite the sun at an angle of 42 degrees relative to our shadow; This is where the rainbow should appear.

Sometimes you can see another, less bright rainbow around the main one. This is a secondary rainbow, which is formed by light reflected in the drops twice. In the secondary rainbow, the order of colors is "inverted" - red is on the inside, purple is on the outside. The secondary rainbow forms at an angle of 50-53° relative to our shadow. The area between two rainbows appears relatively dark because it lacks both single and double reflected rays. The secondary rainbow is weaker than the primary and usually disappears faster.

There is even evidence for a third or tertiary rainbow, but such an occurrence is considered extremely rare. Several observers have also reported seeing quadrangular rainbows, in which the dim outer arc had a rippled, pulsating appearance.

Who first defined what a rainbow is?

We cannot say with absolute certainty who was the first to give the correct explanation of what a rainbow is. Usually the primacy is given to the Frenchman René Descartes (1596-1650), philosopher and writer, who systematically considered this issue in the appendix to his famous work"Discourse on Method" in 1637.

Descartes allegedly made an accurate calculation of the paths that the rays of light passed at different points of a glass globe filled with water (imitation of a raindrop), thereby determining the angles of their refraction. This was the solution to a mathematical problem that eluded scientists for two millennia and was the key to explaining what a rainbow is.

But note that Descartes only "presumably" made this calculation. As it turned out, Willebrord Snell, a Dutch astronomer and mathematician, discovered mathematical law refraction of light 16 years before Cartesian dissertation on the subject. However, Snell was unable to publish his work and died in 1626. Then, about 80 years after Snell's notes were discovered, there was controversy that Descartes somehow saw Snell's manuscripts and passed off the conclusions set out in them as his own.

The end result was that in the West, especially in English-speaking countries, the law of light refraction became known as Snell's Law, and in France it is called Descartes' Law.

So, although Descartes explained what a rainbow is, he really couldn't do it without precise calculations of the refraction of light. But to whom exactly, Descartes or Snell, this part of the work belongs, we may never know.

Where and when can you see a rainbow?

Sailors know that the rainbow can be used to predict the weather. Generally speaking, showers and thunderstorms move from west to east, thus sailors are guided by the old omen:

Rainbow in the morning - be rain; rainbow in the evening - good weather.

In the morning the sun is in the east, and in order to see a rainbow, we must face the west, where it rains. Since rains usually come from the west, the morning rainbow can warn us about this. In the late evening, the sun is in the western part of the sky. After the rain or thunderstorm has already passed over or past us, it usually retreats to the east, where we will see the rainbow.

And since thunderstorms are more frequent in the late afternoon than in the early morning, rainbows are much more common in the evening. It is for this reason that the appearance of a rainbow is usually associated with the beginning of better weather.

If the sun sets or rises, a full arc of the rainbow can be seen. If the sun is 42 degrees or higher above the horizon, we won't be able to see the rainbow because it will be below the horizon. A clenched fist held at arm's length is approximately 10 degrees; so if the sun is about "four fists" above the horizon, we won't see a rainbow. The only way to see the rainbow at this time will be from a plane or from the top. high mountain. Aircraft will provide the best opportunity to see the entire 360-degree rainbow projected onto the ground, but the sight is so rare that few are lucky enough to see it.

People have long thought about the nature of this most beautiful natural phenomenon. Humanity has associated the rainbow with many beliefs and legends. AT ancient Greek mythology, for example, a rainbow is a road between heaven and earth, along which a messenger walked between the world of the gods and the world of people, Irida. In China, it was believed that the rainbow is a heavenly dragon, the union of Heaven and Earth. 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.

Superstitious people believed that the rainbow is a bad sign. They believed that the souls of the dead pass into other world on the rainbow, and if a rainbow appeared, it means someone's imminent death.

The rainbow also appears in many folk omens associated with weather forecasting. For example, a rainbow high and steep portends good weather, and low and flat - bad.

Where does the rainbow come from?

Please note that rainbows can only be observed before or after rain. And only if the sun breaks through the clouds at the same time as the rain. What is happening? The rays of the sun pass through the raindrops. And each such droplet works like a prism. That is, it decomposes the white light of the Sun into its components - the rays of red, orange, yellow, green, blue, indigo and violet. Moreover, droplets deflect light of different colors in different ways, as a result of which white light decomposes into a multi-colored band, which is called spectrum.

The refraction of light as it passes through a prism.
Note that rays of different colors exit the prism at different angles.

The rainbow is a huge curved spectrum. To an observer on the ground, a rainbow usually looks like an arc - part of a circle, and the higher the observer is, the fuller the rainbow. From a mountain or an airplane, you can also see the full circle! Why is the rainbow shaped like an arc?

You can only see a rainbow if you are directly between the sun (it should be behind you) and the rain (it should be in front of you). Otherwise, you won't see the rainbow!

Sometimes you can see another, less bright rainbow around the first one. This is a secondary rainbow in which the light is reflected twice in the drop. In the secondary rainbow, the “inverted” order of colors is purple on the outside, and red on the inside:

To remember the sequence of colors in the rainbow (or spectrum), there are special simple phrases - in them the first letters correspond to the first letters of the color names:

How once Zhak-Z vonar Head C broke Lantern.
To every O hotnik AND does W nat G de FROM goes F azan

Memorize them - and you can easily draw a rainbow at any time!

(!) The first to explain the nature of the rainbow was Aristotle. He determined that "a rainbow is an optical phenomenon, not a material object."

How often do we see rainbows after rain? This colorful spectacle leaves no one indifferent! But when I saw a rainbow in the splashes of the fountain, and then on the wall diagonally from the mirror, I thought, what is the reason for its appearance, if not rain and water? Turning to the teacher for help, I found out that the cause of the rainbow is the phenomenon of dispersion, I found out who studied it for the first time, I understood what it is.

Rainbow is one of the most beautiful natural phenomena which rarely leaves anyone indifferent. Once upon a time, people considered the rainbow to be a sign of God. And this is not surprising, because it appears literally from nothing, and also mysteriously disappears.

What do we know about the rainbow?

The colors of the rainbow are always arranged in the same order from top to bottom: red, orange, yellow, green, blue, indigo and violet (remember from childhood a reminder of the order of colors in the rainbow - Every Hunter Wants to Know Where the Pheasant Sits or How Once Jean Zvonar Blue Broke Flashlight?).

The brightest band is red. Each next color is paler than the previous one. Violet is generally hardly distinguishable against the sky.

What are the constituent parts of a rainbow? These are water droplets in the air, the sun's rays and an observer who sees a rainbow. In this case, a whole ritual must be observed: not only does the sun illuminate the rain, it must be low above the horizon, and the observer must stand between the rain and the sun - with his back to the sun, facing the rain. At this moment, he sees a rainbow. How does this happen?

A sunbeam illuminates a raindrop. Penetrating into the droplet, the beam is slightly refracted. As you know, rays of different colors are refracted in different ways, that is, inside the drop, a white beam breaks up into its constituent colors. This is the phenomenon of dispersion. After passing the drop, the light is reflected from its wall, as from a mirror. Reflected colored rays go in the opposite direction, being refracted even more strongly. The entire rainbow spectrum leaves the drop from the same side from which the sunbeam entered it.

Light from the sun entered the drop from the side of the observer. Now this ray, decomposed into a color spectrum, returns to it. A person sees a huge colored rainbow spread across the sky - light refracted and reflected by billions of raindrops.

Double Rainbow

It is rare to see two rainbows in the sky at the same time. As a rule, the second rainbow is less visible, sometimes barely noticeable. The colors in such a rainbow are inverted, that is, purple comes first. Its appearance is explained by the repeated reflection of light rays inside the drop.

We can also see the rainbow phenomenon when light is refracted by fog droplets or evaporation from the surface of the sea, and in the city - by the fountain.

An experience

A rainbow can also be seen with a water drop.
Plant a drop of water on a stick or blade of grass. Stand with your back to the sun or another bright light source. When the light rays form an angle of about 42 degrees with the direction of the eyes, the transparent drop will suddenly flash with an extremely pure color!
What?
Anyone!
If the drop is carefully moved along the arc of a circle, you can see all the colors of the rainbow!

dispersion phenomenon- decomposition of white light into a spectrum (according to the colors of the rainbow) - was discovered and studied by I. Newton. This phenomenon indicates the complex composition of white light. I went to the London Science Museum for a performance dedicated to Sir Isaac Newton. Having plunged into the atmosphere of the 17th century, having “visited” the scientist’s laboratory (even if it was on stage), I felt like a naturalist.
Take a look at the Museum of Science, learn more about the discoveries made by Newton by clicking on the links below.

A task

Answer : it turns out that the rainbow is visible only when the height of the sun above the horizon does not exceed 42 degrees. On June 22 at noon, the sun is higher in the sky, and there is no way to see a rainbow.

Let's look at an experiment that explains the phenomenon of dispersion and the complex composition of white light.

Wave properties of light. Dispersion.

Interesting fact

From the surface of the earth, a rainbow usually looks like part of a circle, but from an airplane it can also be a whole circle!

Interesting optical physical phenomena: http://class-fizika.narod.ru/w25.htm

You can get acquainted with some optical phenomena by clicking on the link to one of the pages of our school encyclopedia in mathematics and physics "Algorithm of success".

Conclusion

The phenomenon of light dispersion, which explains the causes of the appearance of a rainbow, allowed me to understand why white light paints the world around us with multi-colored colors. We see some transparent objects as red, others as iridescent. different colors. And all thanks to the complex nature of white light, due to the fact that bodies differently reflect, refract and absorb light of different wavelengths. Therefore, they shine and shimmer in sunshine an ordinary piece of transparent glass and a diamond.

Thus, we have proved that we see the rainbow due to the special properties of light waves, and it has its own, interesting explanation, like many other optical phenomena in nature.