1. Why are there so many songs about rainbows? Perhaps it is because this beautiful and short-lived mysterious meteorological phenomenon has inspired our inner romance, perhaps because no one sees the same rainbow.
2. Imagine an imaginary line from the sun, somewhere behind you, connecting your back of your head, eyes and the sun, and extending in front of you, then at an angle of 40 to 42 degrees with this line, usually This is where the rainbow is. Any rainbow you see will revolve around this axis.
3. In fact, if you have a rich experience of watching the rainbow, you will find that the closer to the red part of the rainbow, the more obvious the color, on the contrary, the closer to the blue-purple part, the dimmer the color. Therefore, we generally use an angle of about 42 degrees for the red light wave to find the position of the rainbow.
4. Since the wavelength of light of different colors is different, the rainbow is actually the dispersion of visible light, and the medium is the water droplets in the sky after the rain. When sunlight (including visible light of all wavelengths, displayed as white light together) passes through the water droplets, a rainbow is created.
5. Part of the light is reflected by the outer surface of the water drop, but the rest of the light is inclined with the water drop. Because water is denser than air, it is refracted. When light enters the droplet, its propagation speed slows down and changes direction. (Think about what happens if you are speeding on a highway and the asphalt pavement suddenly becomes a muddy dirt road.)
6. Once inside the water droplet, the light will be reflected by the inner surface of the back of the water droplet and then refracted again , When the light comes out of the water and returns to the air, it will bend. Because the droplet is spherical and its surface is not parallel, the white light emitted will be dispersed into multiple colors. To put it simply, a rainbow is a collection of colored light waves projected into your eyes after the sunlight has “refracted-reflected-refracted” in the small water droplets.
7. Just like Newton used a prism to decompose the seven-color light, when sunlight enters the water droplets suspended in the air at a certain angle, it will also be decomposed into light waves of different colors, and the refractive index of these light waves in the water is different, red light The deflection is the smallest and the purple light is the largest, so water droplets at high places provide red light, and water droplets at low places provide blue-violet light. In the end, we see a colorful rainbow with red at the outermost circle and blue-violet at the innermost. The colors are red, orange, yellow, green, blue, indigo, and purple.
8. However, if the light is reflected once more in the water droplet, that is, “refraction-reflection-reflection-refraction”, then the order of the colored light waves will be reversed, which is the neon in the “double rainbow”. Because there are too many round trips between each interface, the energy of the light is lost, so the brightness of the neon we see is much smaller than that of the rainbow.
9. The color gradation of the rainbow is continuous without obvious color separation. However, humans like to organize things, including colors, to make them meaningful. Researchers believe that this is why our brain divides the arcuate spectrum into different bands. The exact mechanism by which the human eye sees the streak, and whether it is in the brain or the eye, is still unknown.
10. The number of colors a person “sees” in the rainbow depends on expectations, and expectations are the product of culture. In most extant medieval manuscripts with rainbows, the colors of the rainbow are generally only three colors, and no more than five colors at most, and the order of the color layers is often different from the natural order.
11. Aristotle only wrote about the three colors of the rainbow: red, green and purple. Some early Islamic scholars also saw the tricolor rainbow, but it was red, green and yellow. Bartholomew was influenced by Aristotle and others, who believed that the rainbow should be four colors, corresponding to the four elements of earth, fire, water and wind.
12. Roger Bacon, a primitive scientist in the Middle Ages, described five colors. Bacon believed that the rainbow itself should be red, blue, and green. It was not until the 17th century that Sir Isaac Newton connected the perceived colors in the rainbow to the notes in the scale of Western music that European scientists agreed that the rainbow had seven colors.
13. Another thing to note is that the rainbow is not actually a semicircle as people think, but a complete circle. In other words, the rainbow has no beginning and no end. The center of the rainbow is the midpoint of the vertical line between the sun and the earth, and what can be projected into the eyes and seen by you is the aggregate of light beams at about 42 degrees from the parallel incident light. The rest is below the horizon, so people can’t see it. But there are exceptions. For example, you can see a more complete rainbow in the sky!
14. The sun illusion is an optical phenomenon of the atmosphere. In the translucent thin clouds that appear in the sky, there are hexagonal column-shaped ice crystals floating in the air, sometimes neatly and vertically arranged in the air. When sunlight hits these hexagonal icicles, a very regular refraction occurs. It first refracts around the sun and then hits human eyes. It looks like multiple suns. This is after sunlight is refracted by ice crystals. The resulting light image, when densely covered with ice crystals in the sky, you can often see a touch of colorful light and shadow on the left and right of the sun.
15. The flame rainbow cloud has nothing to do with the rainbow. It is neither a fire nor a rainbow, but it is definitely an extremely spectacular natural scene. According to the National Aeronautics and Space Administration of the United States, the scientific name of the colorful flame cloud is called the rainbow cloud. It is a very rare natural phenomenon. This phenomenon is caused by the accumulation of a large number of water droplets of uniform size in the cloud. These clouds diffract sunlight in a similar way, and then emit sunlight of different wavelengths.
16. This makes them look a bit like the colorful rays of the rainbow. These colorful rays are formed due to diffraction. It is also due to diffraction that the color of the colorful clouds changes from blue to green to red to purple to green. endless. Although the rainbow cloud has a rainbow-like light, it is not the same way as a rainbow. Rainbows are formed due to refraction and reflection, and rainbow clouds are formed due to diffraction.
17. The reason why the rainbow holds a big place in the myth is because of its beauty and its incomprehensible magical phenomenon. Until Galileo’s monograph on the characteristics of light appeared, people could explain the phenomenon of rainbow. In Chinese mythology, Nuwa refines the five-color stone to fill the sky, and the rainbow is the color light emitted by the five-color stone.
18. In the West, in Greek mythology, the rainbow is a messenger between heaven and earth; in Irish folklore, the dwarf collects the treasure at the end of the rainbow; in Indian mythology, the rainbow is the bow of the thunder god “Indra”; In Norse mythology, the rainbow bridge connects the realm of the gods “Yasget” and the human settlement “Middle-earth”. According to the Bible, the rainbow is a sign of God’s promise to mankind that he will never drown the earth again.
19. In ancient times, Christianity spread in the West. For those believers, light was a very sacred thing. They regarded light as a product of God, and believed that the first thing born in the world was light, and it was light that gave birth to people. Therefore, believers also regard light as a tool for preaching doctrine.
Refraction breaks light into multiple colors
Although sundogs and the halo surrounding the sun are beautiful, they are not rainbows.
Three-color rainbow, God and Noah made a covenant with the rainbow (6th century manuscript).
20. Roger Bacon is a Christian, but at the same time he is also a great optical researcher. He used science to explain the sacred objects that people have always believed to be a product of nature, but no matter what amazing experiments he made in public, people only heard that he denied the miracle, and the religious imprisoned him and detained him entirely. Twenty years, but he still did not give up research, and his papers in prison have been handed down.