What is the phenomenon and principle of the rainbow connecting Shenzhen and Hong Kong?

After the rain, we sometimes see colorful rainbows in the sky, which are very beautiful. Recently, the rainbow from Shenzhen to Hong Kong has exploded the circle of friends, so do you know what a rainbow is? The principle of formation? Next, let's reveal the constellation knowledge for everyone!

Rainbow from Shenzhen to Hong Kong On June 16, netizens photographed a giant rainbow from Shenzhen Bay in China to Hong Kong New Territories in China. The netizen exclaimed: This is the most beautiful overpass I have ever seen!

What is the rainbow phenomenon? Rainbow is an optical phenomenon in meteorology. 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, just after the rain clears. At this time, there is little dust in the air, all of which are water droplets. One side of the sky is dark because there are still rain clouds, but the head or back of the observer is no longer covered by clouds, so that the rainbow can be easily seen. Another place where rainbows are often seen is near waterfalls. In sunny weather, you can also spray water or spray into the air with your back to the sun to make artificial rainbows. Moon rainbow, also known as night rainbow, is a very rare phenomenon, which may appear in the night with strong moonlight. Because it is difficult for human vision to distinguish colors in low light at night, the night rainbow looks as if it is all white.

The principle of rainbow is that sunlight shines on nearly spherical water droplets in the air, resulting in dispersion and reflection. When sunlight hits a water drop, it is incident at different angles 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 kind of 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, totally reflecting once and refracting twice. Because water has a dispersive effect on light, the refractive index of light at different frequencies is different. The refractive index of red light is smaller than that of blue light, but the deflection angle of blue light is larger 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. So rainbows and neon lights have different heights, and the layering order of colors is just the opposite. Rainbow light is refracted twice and reflected once, while neon light is refracted twice and reflected twice.

Multiple rainbows Most people don't notice neon because they don't take the initiative to observe it. Neon is a dim sub-rainbow, which often appears outside the main rainbow. Neon is produced by two reflections and two refractions of sunlight in raindrops, and the angle of light is 50-53. As a result of two reflections, the color arrangement of neon is opposite to the arc of rainbow, with blue outside and red inside. Neon lights are darker than rainbows, because two reflections not only make more light escape, but also spread to a wider area. The dull sky between rainbows and neon lights is named Alexander Belt because it was first described by Alexander. The darker third rainbow, even the fourth rainbow, was photographed. These are all caused by sunlight reflecting in raindrops three or four times. These rainbows all appear on the same side of the sun in the sky. The third road is about 40 from the sun, and the fourth road is about 45. It is difficult to see with the naked eye because of the sunlight. Felix Bell described the high-order rainbow. He described the location of the 19 rainbow and called this pattern "Rainbow Rose". In the laboratory, higher-order rainbows can be observed by using brighter light and collimated laser. It is reported that many people, such as Wu, used an argon ion laser beam in 1998 to achieve a rainbow of 200 levels in a similar way.

Reflective Rainbow and Reflective Rainbow When a rainbow appears on an object on the water surface, two complementary mirror arcs from different optical paths may appear on the water surface and underwater respectively. Their names are slightly different. If the water surface is calm, the reflected rainbow will appear as a mirror image below the horizon of the water surface. Before sunlight reaches the observer, it will be deflected by raindrops and then reflected by the water surface. Even in a small puddle, the reflected rainbow, at least a part of it, is often visible. When sunlight is reflected by the water surface before it reaches the raindrops, it may produce a reflected rainbow. If the water surface is large enough and the whole water surface is calm and close to the rain curtain, the reflected rainbow may appear above the horizon. It meets the normal rainbow at the horizon, and its arc will be higher in the sky because its center is above the horizon, while the center of the normal rainbow is below the horizon. Due to the above conditions, reflected rainbows are very rare. If the reflex arc is reflected again, neon reflex arc and other reflex arcs appear at the same time, and it is also possible that six color bands appear at the same time.

Circular Rainbow A circular rainbow is caused by the "internal reflection" of raindrops on sunlight, because the refractive index of raindrops is different from that of air.