What is a rainbow like?

Rainbow is the aperture of red, orange, yellow, green, blue, indigo and purple from the outer ring to the inner ring.

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. At this time, there is less dust in the air and it is full of water droplets. One side of the sky is dark because there are still rain clouds, but there is no cloud cover on the observer's head or behind, so the sun can be seen, so the rainbow will be easier to see.

cause

Rainbow is formed by the scattering and reflection of sunlight on spherical water droplets in the air. 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 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, which is a total of one reflection and two refractions.

Because water has a dispersive effect on light, the refractive index of light with different frequencies is different. The refractive index of red light is smaller than that of blue light, and 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 the heights of rainbows and neon lights are different, and the hierarchical order of colors is just the opposite. Rainbow means that light is refracted twice and reflected once, while neon means that light is refracted twice and reflected twice.