Why is the water in the swimming pool blue and white?

First of all, you have to understand a truth: the things around us are colored only because the sun shines on them. Although sunlight looks white, all colors: red, orange, yellow, green, cyan, blue and purple exist in sunlight.

If you think of light as a wave, you will solve the mystery. Light actually moves like a wave. Let's imagine a drop of rain falling in a puddle. When this drop of rain falls on the water, it will produce small waves, which will fall into a larger circle and spread in all directions. If these waves hit pebbles or other obstacles, they will bounce back and change the direction of the waves.

When the sun falls from the sky, it will continue to encounter some obstacles. Because the air that light must penetrate is not empty, it is made up of many tiny particles. Ninety-nine percent of them are either nitrogen or oxygen, and the rest are other gas particles and tiny floating particles, which come from automobile exhaust, factory smoke, forest fires or volcanic ash. Although oxygen and nitrogen particles are only one millionth of a drop of rain, they can still block the path of sunlight. The light bounced back from these small stumbling blocks and naturally changed direction.

But so many colors of light have changed direction, why only see blue? You probably still don't understand.

We must go back to the puddle we just talked about.

In a puddle, if a small wave meets pebbles, the water surface will be chaotic; But if it is a "huge wave", just like the kind of "huge wave" that you lift by hand at the edge of the puddle, it may simply overflow from the stone and reach the edge opposite the puddle unimpeded. Then, just like there are big waves and small waves, all kinds of light waves have different "waves", that is, wavelengths: but unlike water waves, their size is invisible to the naked eye, because they are incredibly small, only 1% of a hair! You have to use very sensitive measuring instruments to measure accurately.

According to the determination of scientists, the wavelengths of blue light and purple light are relatively short, which is equivalent to "wavelet"; The wavelengths of orange light and red light are relatively long, which is equivalent to "big waves". When encountering obstacles in the air, blue light and purple light are "scattered" everywhere because they can't cross those obstacles, covering the whole sky-the sky, so they are "scattered" into blue.

The scientist who discovered this "scattering" phenomenon is called Rayleigh. He discovered it about 130 years ago, and he is also a Nobel Prize winner.