In summer, after the rain, the dark clouds fly away and the sun reappears. In the sky opposite the sun, there will be a semi-circular rainbow.
Rainbow is formed because sunlight is emitted in the air and refracted into water droplets.
We know that when sunlight passes through the prism, the direction of the foreground will be deflected and the original white light will change.
The line is broken down into seven color bands: red, orange, yellow, green, cyan, blue and purple.
After the rain, there are many tiny water droplets floating in the air. When the sun shines on them, they will refract and disperse.
Into seven colors of light. Many small water droplets refract sunlight at the same time, and then reflect into our eyes, and we will see one.
A semicircle rainbow. The ribbons of the rainbow are distinct, and the red ones are on the outermost side, followed by orange, yellow, green, cyan, blue and purple.
Color.
The size of water droplets in the air determines the bright color and width of the rainbow. When the water drops in the air are large, the rainbow is bright. also
Relatively narrow; On the contrary, if the water drops are small, the rainbow will be light and wide.
We can't see the rainbow when facing the sun, but only when facing the sun can we see the rainbow, so the rainbow in the morning appears.
In the west, the rainbow at dusk always appears in the east. But we can't see it. We can only see it from the sky by plane.
The appearance of rainbow is related to the weather change at that time. Generally, we can infer from the position of the rainbow in the sky that it will appear at that time.
It is sunny or rainy. When there is a rainbow in the east, it is not easy to rain locally, and when there is a rainbow in the west, it may rain locally.
Very sexual.
The visibility of rainbow depends on the size of water droplets in the air. The bigger the water drop, the brighter the rainbow, and the smaller the water drop, the less obvious the rainbow is. Generally, in winter, the temperature is low, there are few water droplets in the air, and there are few opportunities for showers, so rainbows generally do not appear in winter.
Question 2: How is the rainbow formed? Rainbow is a natural light phenomenon that people often see.
Because there are a lot of small water droplets floating in the air. When the sun shines on these small water droplets, one by one, like a prism, decomposes the white light into seven single beams, which have dispersion effect on the sun.
Sunlight enters water droplets, that is, it enters water from the medium of air and undergoes a refraction. Due to the different refractive indexes of various monochromatic lights that make up white light, violet light has the shortest wavelength and the largest refractive index, red light has the longest refractive index and the smallest refractive index, and other colored lights are in between. Therefore, the light is split in the water drop, and the light of various colors continues to spread in the water drop at the same time, and is reflected back when it meets another interface of the water drop, passes through the inside of the water drop again, and refracts back into the air when it comes out. In this way, the sunlight in the water drops undergoes twice refraction and once total reflection, and is decomposed into seven monochromatic lights: red, orange, yellow, green, blue, indigo and purple. When there are a large number of water droplets in the air, sunlight passes through these water droplets, and after reflection and refraction, the emitted light gathers together to form a beautiful rainbow in the sky.
Question 3: How is the rainbow formed? Rainbow is an optical phenomenon in meteorology. When sunlight hits the raindrops in mid-air, the light is refracted and reflected, forming an arched color spectrum in the sky. There are different opinions about which seven colors the rainbow is. China is the most common (from outside to inside): red, orange, yellow, green, cyan, blue and purple. The western saying is: red, orange, yellow, green, blue, indigo and purple are the names taken by scientist Newton after decomposing seven primary colors.
In fact, as long as there are water droplets in the air and the sun shines behind the observer at a low angle, an observable rainbow phenomenon may occur. Rainbow usually appears in the afternoon, when the rain clears. At this time, the air is less dusty and full of water droplets, and one side of the sky is dark because of rain clouds. However, observers can see the sunlight without being covered by clouds above or behind them, so rainbows are easier to see. Another place where rainbows are often seen is near waterfalls. When the weather is clear, you can spray water or mist into the air with your back to the sun, or you can make rainbows artificially.
Sunset is a rare phenomenon, which may appear in the night with strong moonlight. Because it is difficult for human vision to distinguish colors in the case of weak light at night, the night rainbow looks all white.
principle
The optical principle of rainbow is that sunlight shines on small round water droplets in the air, resulting in dispersion and reflection. When sunlight enters the water drop, it will be incident at different angles at the same time and reflected at different angles in the water drop. The reflection of 40 to 42 degrees is the strongest, which produces the rainbow we see. When this reflection occurs, sunlight enters the water drop, refracts once, then reflects on the back of the water drop, and finally refracts again when it leaves the water drop. Because water has a dispersive effect on light, the refractive index of light with different wavelengths is different, and the refractive angle of blue light is greater than that of red light. Because light is reflected in water droplets, the spectrum seen by the observer is reversed, with red light at the top and other colors at the bottom.
Double rainbow, neon above, rainbow below. Many times, two rainbows appear at the same time, and a concentric but darker secondary rainbow (also called neon) appears outside the usual rainbow. The secondary rainbow is formed by two reflections of sunlight in water droplets. The strongest reflection angle of the two reflections occurs at 50 to 53, so the position of the secondary rainbow is outside the main rainbow. Because there are two reflections, the color sequence of the auxiliary rainbow is opposite to that of the main rainbow, with the outer side being blue and the inner side being red. In fact, the auxiliary rainbow must follow the main rainbow, but sometimes it is invisible to the naked eye because of its low light intensity (see).
The rainbow does not actually appear in a specific position in mid-air. It is an optical phenomenon seen by the observer, and the position of the rainbow will change with the observer. When an observer sees a rainbow, its position must be in the opposite direction of the sun. The center inside the rainbow arch is actually an enlarged image of the sun reflected by water droplets. So the sky inside the rainbow is brighter than the sky outside the rainbow. The center of the rainbow arch is just the direction of the observer's head shadow, and the rainbow itself is 40 to 42 degrees above the line between the observer's head shadow and his eyes. Therefore, when the sun is higher than 42 degrees in the sky, the rainbow will be below the horizon and invisible. This is why rainbows rarely appear at noon.
The rainbow extends from one end to the other. With an ordinary 35mm camera, you need a wide-angle lens with a focal length below 19mm to capture the whole rainbow in a single frame. If you are on an airplane, you will see that the rainbow will be a complete circle instead of an arch, and the center of the circular rainbow is the direction of the airplane.
In 1307, it was suggested in Europe that rainbows are caused by the refraction and reflection of sunlight by water droplets. Descartes found in 1637 that the size of water droplets does not affect the refraction of light. He experimented by injecting water into the glass ball and got the refractive index of water to light. He mathematically proved that the main rainbow is caused by reflection at the water point, while the auxiliary rainbow is caused by two reflections. He calculated the angle of the rainbow accurately, but failed to explain its colorful colors.
Later, Newton discovered all the optical principles of rainbow formation after scattering sunlight into color with a glass rhombus.
Question 4: How is the rainbow formed? How is the rainbow formed?
In fact, as long as there are water droplets in the air and the sun shines behind the observer at a low angle, an observable rainbow phenomenon may occur. Rainbow is formed by the dispersion and reflection of sunlight on small round water droplets in the air. When sunlight enters a water drop, it will be incident at different angles at the same time and reflected at different angles in the water drop. Among them, the reflection of 40-42 degrees is the strongest, forming a rainbow that people see. Rainbow usually appears in the afternoon, when the rain clears. At this time, the air is less dusty and full of water droplets, and one side of the sky is dark because of rain clouds. However, observers can see the sunlight without being covered by clouds above or behind them, so rainbows are easier to see.
Generally speaking, the appearance of rainbows is closely related to the weather. People can infer whether it was sunny or rainy from the position of the rainbow in the sky. When there is a rainbow in the east, it is not easy to rain locally, but when there is a rainbow in the west, it is likely to rain locally.
Question 5: What is the principle of rainbow? After a thunderstorm or shower in summer, a very beautiful bow-shaped ribbon often appears in the sky. Seen from its outer layer, the seven colors of red, orange, yellow, green, blue, indigo and purple are arranged neatly. This is a rainbow. Just after the rain, there are many small water droplets floating in the air, which are refracted and internally reflected by sunlight, while the visible light of the sun-red, orange, yellow, green, blue, indigo and purple-has different wavelengths. When they shine on these water droplets in the air, the light of each color is refracted by the water droplets in different ways, and then it is decomposed into seven colors to form a rainbow. Because of this, the position of the rainbow is always relative to the position of the sun, appearing in the west in the morning and in the east in the afternoon. The color of rainbow is closely related to the particle size of water droplets. When the water drops are big, the rainbow will be clear and bright, and when the water drops are small, the rainbow will not be so bright. Knowing why there is a rainbow, you can "make" one yourself: take a sip of water and spit it out with your back to the sun. Look at the seven-color rainbow clearly appearing on the water drop. Try it if you don't believe me. In our daily life, sometimes colorful rainbows appear in the sky after rain, so why do rainbows appear after rain? Why do rainbows have seven colors? I started my research with these questions. At first I thought, "Rainbow appears after rain, and it must be related to rain." So I brought a shower head, and then let the water flow for artificial rainfall. It rained, but the rainbow didn't "show up". This is the watering can I thought of for watering flowers at ordinary times. I found it, and then changed the nozzle of the watering can into the shape of fog, and then sprayed water like fog. After a while, the rainbow finally appeared. After many experiments, I also found that rainbows only appear in the sun, so rainbows must be related to the sun. I asked my brother what was going on, and he said, "The sun itself is made up of red, orange, yellow, green, blue and purple. Small water droplets in water vapor can decompose sunlight like a prism, so rainbows will appear where there is a lot of water vapor. " Oh, I see! Now I think I finally figured it out, so I quickly wrote it out and gave it to the teacher. After reading it, the teacher said, "I don't study deeply, let me continue my study." Why can a prism decompose sunlight? " I have no choice but to go home and go online with my brother to find the answer. On the internet, my brother and I searched and searched, but we couldn't find it. I cast the net eight times and didn't catch any fish. Had to return in vain. When I got to school, I told the teacher the result. The teacher didn't believe that I couldn't find the answer, so she left me behind after school to help me check the information online. After looking up one noun after another on the Internet, I finally saw a message titled "How does a prism decompose sunlight". The teacher said happily, "This is a play!" We opened this webpage and read it carefully before we understood it. There are seven colors of light in a beam of sunlight. When light passes through a prism or water vapor, the light will be scattered due to the different refraction angles of each light. Red has the smallest refraction angle, so at the top, purple has the largest refraction angle. So at the bottom, when it rains, the dense water vapor in the sky prospers a prism with a large surface and decomposes the sunlight. So the rainbow is formed like this!
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Question 6: How is the rainbow formed? Rainbow is formed when sunlight penetrates rain particles. Originally, light travels in a straight line, but once it enters the water, it also has the property of refraction. So sunlight will be refracted when it passes through rain particles. At this time, because the angle of light refraction varies with different colors, seven colors will be shot at different angles. So the seven colors will be arranged beautifully. This is the principle of forming a rainbow.