why the sea is blue ???

 If you have the chance to walk on a beach, you only see that: the sublime blue of the sea. But, by the way: why this color? Find out why the sea is blue.

If the Earth is called "the Blue Planet", it is no coincidence: 71% of it is covered with water of a beautiful blue color clearly visible from space.

Reflection of the blue light of the sky on the sea

Where does this blue color come from? There are two reasons. The first, which seems the most obvious but is not the most important, is the reflection on the sea surface of the diffuse light from the sky, responsible for the blue color of the sky.

This is why the sea is bluer in good weather, when the sky itself is blue, and it is rather gray in bad weather, when it is also gray.

Absorption of wavelengths: all that's left is blue!

However, speleologists have found that even in caves, protected from the sky, the water is blue if it is illuminated with a white light. Indeed, when a white light, in other words solar radiation, hits the surface of the water, part is reflected (the first reason for the blue color of the water surface) and the other is refracted and penetrates into the water.

However, white light is in fact made up of several wavelengths, each responsible for a color in the visible spectrum. This is why the light refracted by the raindrops forms a multicolored rainbow. Not every wavelength (color) is absorbed as quickly by water molecules.

It is the red and yellow waves that disappear first, between 10 and 30 meters deep. At around 60 meters, the green disappears in turn and only the blue remains, which ends up being absorbed at a depth of 90 meters. Therefore, the color that is most refracted by the sea is blue, which explains its color.

Sometimes when the waters are rich in photosynthetic phytoplankton, the blue waves are absorbed more quickly by the chlorophyll and the sea takes on a green undertone, as this is the only visible wavelength that remains.