The main difference between rainbow and neon.

In the hot summer, after a heavy rain, sometimes we can see a colorful ring across the north and south, hanging in the air, which is the rainbow. Sometimes you can see a second rainbow on the outside of the rainbow, which is slightly brighter than the first rainbow and is called a sub-rainbow or neon. Rainbow and neon are in the opposite order. The color sequence of rainbow is outer red and inner purple, while the color sequence of neon is outer ultraviolet and inner red.

In China, as early as Oracle Bone Inscriptions in the Shang Dynasty, there were records about rainbows. The ancients thought that the rainbow was the appearance of the dragon after the rain, so they put the word rainbow next to the word "worm" and it has been used ever since. In fact, rainbows are formed by small water droplets floating in the air reflecting sunlight. If we stand with our backs to the sun on a sunny morning or evening, and then spit into the air with our mouths, we will see a small rainbow on those water drops. In the air after a heavy rain, there are many small water droplets like this floating in the air. They are like prisms hanging in the air. When the sun passes through them, it is first decomposed into seven colors: red, orange, yellow, green, cyan, blue and purple, and then reflected back. At this time, if someone stands between the sun (near the horizon) and the "rain curtain" formed by raindrops, they will see colorful rainbows. If the sun is refracted and reflected by water drops twice, there will be neon lights with slightly lighter colors and opposite arrangements outside the rainbow.

The brightness of the rainbow and the width of the rainbow band are related to the size of water droplets in the air. When the water drops are large, the rainbow is bright and clear and narrow; If the water drops are small, the rainbow will be light and wide. If the water drop is too small, there may be no rainbow.

Rainbow mainly appears in summer and is rare in winter. This is because there are many thunderstorms and heavy raindrops in summer. Often after a shower, it clears up quickly, and there are many small water droplets floating in the air, which form a rainbow after being irradiated by the sun. In winter, the weather is generally dry, there are fewer opportunities for rain and fewer showers, so it is difficult to see rainbows in winter.