When you are on the beach, you can only pick up the sea water. It is no different from ordinary water. It is transparent and colorless. Then why does the sea look completely different from the transparent color?
Why is the sea blue
In fact, this is the sun's magic. We know that sunlight is composed of seven colors: red, orange, yellow, green, green, blue and purple. When sunlight shines on the sea, red and orange light with longer wavelength can overcome obstacles and move forward bravely due to their maximum transmission force. As they move forward, they are constantly absorbed by seawater and organisms in the ocean. Blue light and purple light, due to their shorter wavelengths, scatter in all directions and even are reflected back when encountering the obstruction of sea water. Only a small part of them are absorbed by sea water and sea surface organisms.
The sea looks Du blue because the scattered and reflected blue and purple light enters our eyes. The deeper the water, the more blue Dao light is scattered and reflected, and the bluer it looks.
In fact, clean fresh water is also blue for the same reason as the above. Most of the water we usually see is green, mainly because the water body contains a lot of green algae. For example, in the Red Sea, there is a kind of algae growing in the water, which appears seasonally. After these algae die, they are reddish brown. Therefore, the Red Sea is also named, but the Red Sea is not red.
Why is the sea blue?
As we all know, there are seven colors of visible light: red, orange, yellow, green, blue, cyan and purple, but the wavelengths of light are different, and seawater is easy to absorb light with longer wavelengths, such as red, orange and yellow, while the corresponding green, cyan, blue and purple are not easy to be absorbed, especially blue and purple are most likely to be scattered and reflected, Therefore, when the sun shines on the sea, it is basically blue and purple.
So, the question comes, since the color of the sea is blue and purple, why do we see blue? It turns out that people's eyes are also very picky. They are very insensitive to purple and often turn a blind eye. They are just sensitive to blue. Therefore, in people's senses, the sea water is blue.
Why are some sea water blue and some green
The color of water depends on the absorption and reflection of light by water molecules. Sunlight is a mixture of seven colors of light, also known as spectrum. In the spectrum, the light near the wavelength range from red to green is easily absorbed by water molecules, and the light in the blue part will be reflected, so what we see is blue.
However, the color of the water is not always the same. The farther away from the center of the sea area along the coast, the sea water is dark blue, and some even purple. However, along the coastline near the land, the color of the sea water changes from blue to green and from green to yellow green. Why is there such a change? It has something to do with the floating matter in the water and the depth of the water.
Sea water can not only be described as blue. The color of the sea in different places will also change a lot. Near the coastline, there are a lot of organic matter and aquatic biomass from the land in the sea, including some small green substances called plankton. They contain a chemical substance of chlorophyll, which can absorb most of the red and blue light and reflect green light, So we see that the sea water along the coast is green.
In the universe, the color of the ocean allows us to distinguish the gathering area of life on earth. The green ocean area is like the tropical rain forest on land, full of life; The dark blue sea is a place where there is little life. It is like an uninhabited desert on the mainland.
The absorption of light by seawater and planktonic substances in seawater will also change the color of the water surface. Suppose you are driving a yellow submarine. Near the water surface, your submarine is yellow, but the submarine slowly dives into the seabed and less and less light shines on the submarine. When the submarine drops to a depth of 30 meters underwater, almost all the yellow, orange and red lights in the sun are absorbed by water molecules. Only the blue and green lights can reach the surface of the submarine, and then your submarine becomes blue-green. If you go down again until the green light disappears, the submarine will turn dark blue.
The more plankton, the more turbid the sea water, and the more light it absorbs. So the more turbid the water is, the faster you will see the surrounding environment darken as you descend.