What color is the sea?

The sea is blue, and the sea water is transparent, but it reflects ultraviolet rays and thinks it is blue.

At the seaside, the endless sea is blue. However, when you scoop up a basin of seawater and observe it, you will find that the seawater is colorless and transparent. Where does the blue of the sea come from?

Selective absorption is the main reason for the appearance of color. In a certain wavelength range, if a substance absorbs the light of various wavelengths passing through it in the same amount (refers to energy) and the absorption amount is small, it is called general absorption; A substance is said to have selective absorption if it significantly absorbs light energy of a certain wavelength. When sunlight hits the sea, part of the light is reflected back and the other part is refracted into the water. The light entering the water will be absorbed by the water during its propagation. The absorption of light by water is related to the wavelength of light, that is, water has selective absorption. Water significantly absorbs light with longer wavelengths, but does not absorb light with shorter wavelengths. Red light, orange light and yellow light are all absorbed at different depths, and the temperature of seawater rises. At a certain depth, green light is also absorbed. Blue light and purple light with shorter wavelength will scatter or reflect back in all directions when encountering water molecules or other particles. Therefore, when the sea is clear and transparent, the blue light and purple light that are least absorbed by the sea are reflected and scattered into our eyes, and the sea we see appears blue.

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