When describing the ocean, people often write that the sea is blue, but not everyone knows why the sea is blue.
Sea water is not born blue. If you scoop a little seawater-whether it's the South Pole or the North Pole, whether it's the Pacific Ocean or the Atlantic Ocean-it will be colorless and transparent in the laboratory. And most of the sea water is so blue and lovely, which is completely dressed by the skillful hands of the sun.
Sunlight consists of seven monochromatic lights: red, orange, yellow, green, blue, indigo and purple. When these seven kinds of light walk side by side, no one can see their true colors clearly. Only when they run from one substance to another, or encounter very small obstacles, the shorter the wavelength, the stronger the scattered light. For example, violet light and blue light scatter or refract back from one substance to another, or when encountering obstacles. This is the case with seawater. Its color not only changes with depth, but also often changes its composition. Every water molecule, every tiny sediment, is like a guardian, guarding the door of seawater and not letting light in.
In the sun, the wavelengths of red light and orange light are longer. They seem to have long legs and can bypass all obstacles and go forward bravely. They are constantly absorbed by seawater in the process of advancing, which makes the temperature of seawater rise and evaporate. Blue light and purple light will scatter in all directions when encountering obstacles, or simply reflect back.
The deeper the sea water is, the more blue light is scattered and reflected, and we look as blue as enamel solution.