There are rainbows in Beijing for three consecutive days. How is the rainbow phenomenon formed?

In middle school physics, when it comes to natural light, also known as white light, when it passes through a prism, light dispersion will occur, and white light will become seven-color light. Therefore, there are a lot of water molecules in the air after the rain, just like countless prisms, which lead to the scattering of sunlight when it passes through.

The specific reason is that light itself propagates along a straight line, but it will be deflected after entering the medium. Therefore, when sunlight passes through raindrops, due to different deflection angles, different rays are arranged into seven colors of red, orange, yellow, green, cyan, blue and purple according to their respective wavelengths. Since light is reflected in water droplets, from the observer's point of view, the spectrum should be reversed, so the red light with the longest wavelength is arranged at the outermost.

The size of water droplets in the air also determines the brightness and width of the rainbow. Generally speaking, the bigger the water drops in the air, the brighter the color and the narrower the width of the rainbow. On the contrary, the smaller the water drop, the lighter the color and the wider the width. Generally speaking, the rainbow appears in the sky opposite the sun, so the rainbow usually appears in the west in the morning and in the east at dusk. At this time, we can't see it, and we can only see it if we fly down from a height. Therefore, if we want to see the rainbow after rain, we must turn our backs on the sun.

Temperature also has a certain influence on the rainbow. In winter, there is less water in the air, so there is less chance to take a shower, so there is generally no rainbow, but in summer, it is the opposite.

The proverb says:

Stay indoors at sunrise and travel thousands of miles at sunset. In fact, the appearance of rainbow can also predict the change of weather. Generally speaking, if the rainbow appears in the east, it is not easy to rain locally, but if it appears in the west, it is likely to rain.

Besides, rainbows appear not only in the daytime, but also at night, but not in the daytime, but in the moonlight. Similar to the sun rainbow, the formation of the moon rainbow also needs a light source. Although there is no sun, if the moonlight is bright and there is a proper amount of water in the atmosphere, a rainbow can also be formed.