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ّForm the book by James McBride, see The Color of Water

 why the sea water is blue

 

 

The color of water is a subject of both scientific study and popular misconception. While relatively small quantities of water are observed by the human eye to be transparent, pure water has a light blue color which becomes a deeper blue as the thickness of the observed sample increases. The blue color is caused by selective absorption and scattering of the light spectrum. Impurities dissolved or suspended in water may give water different colored appearances

Color of lakes and oceans

 Large bodies of water such as oceans manifest water's inherent slightly blue color, not a reflection of the blue sky, as was once believed

It is a common misconception that in large bodies, such as the oceans, the water's color is blue due to the reflections from the sky on its surface. This is not true, but was believed to be so decades ago. The main reason the ocean is blue is that water itself is a blue-colored chemical. Optical scattering from water molecules provides a second source of the blue color, but colored light caused by scattering only becomes significant with extremely pure water According to the frequency spectra for pure liquid water, a short water column has a very light shade of turquoise blue. Thicker layers (many meters) appear much darker blue. It is only when collected in a large body that water's blue color becomes apparent

If the oceans owed their color to the sky, they would be a lighter shade of blue and would be colored white on cloudy days. Some constituents of sea water can influence the shade of blue you see in the ocean. This is why it can look greener or bluer in different areas. A swimming pool with a white painted bottom should look white, yet the water appears turquoise blue, even as it is observed in indoor pools where there’s no sky to be reflected. The reason why water is a blue colored substance involves the theory of radioactive transfer (absorption and scattering), and material electromagnetic spectra

 Scattering from suspended particles also plays an important role in the color of lakes and oceans. A few tens of meters of water will absorb all light, so without scattering, all bodies of water would appear black. Because most lakes and oceans contain suspended living matter and mineral particles, known as colored dissolved organic matter (CDOM) light from above is reflected upwards. Scattering from suspended particles would normally give a white color, as with snow, but because the light first passes through many meters of blue-colored liquid, the scattered light appears blue. In extremely pure water as is found in mountain lakes, where scattering from white colored particles is missing, the scattering from water molecules themselves also contributes a blue color

One other phenomenon that occurs is Rayleigh scattering in the atmosphere along one's line of sight: the horizon is typically 4-5 km distant and the air (being just above sea level in the case of the ocean) is at its densest. This mechanism would add a blue tinge to any distant object (not just the sea)     because blue light would be scattered into one's line of sight

 

 

 

 

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با سلام، بیائید زمین را پاک بداریم dear all, lets care more about our environment
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