Water is clear. Why is snow white?

Water appears blue for the same reason the sky appears blue. It refracts shorter wavelength light (violet and blue) more than all other colors so if you shine white light (containing all colors) through it the blue light gets refracted in many directions while the other colors pass straight(er) through. If you look at the sun directly at midday, it appears mostly white perhaps with a tiny bit of blue subtracted. When you look at the sky away from the sun, some of the blue light from the sun passing through it, is refracted toward you while the rest of the colors pass straight(er) through. If you look at the sun low on the horizon when the sunlight has to pass through much more atmosphere (tens or even hundreds miles) to reach you, then much more of the blue and green and sometimes even a little yellow is refracted away leaving red and orange, while the sky away from the sun appears an even deeper blue. This effect is much stronger in water, but you rarely look at a white light through water, so it's the equivalent of always looking at the sky away from the sun. Most colors pass straight through, but a lot of blue is refracted toward you. The thicker the body of water, the deeper blue it will appear because the light has more chances to be refracted.

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