In high altitude or high latitude areas, it usually snows in winter, making the land appear white and beautiful. But I wonder if anyone has ever wondered why the snow is white?
According to the Live Science website, this question is related to optics. The first thing to understand is the substance that makes up snow, which is water. It is a substance that is naturally clear and transparent, but can take on a white appearance.
Kenneth Libbrecht, a physics professor at the California Institute of Technology, said the glass in a window is clear, but when you use a hammer to break it into small pieces of broken glass, it turns white.
The difference, Libbrecht said, is mainly in how light interacts with a single surface like a window and multiple surfaces like broken glass, and the same concept can be applied to snow.
According to optics, when light touches an object, it either travels through it, or is absorbed or reflected by it. When light touches a smooth surface like glass or ice, its visible light usually penetrates the surface without interference in its path.
Since the human eye sees only the light waves absorbed or reflected by the object, glass and ice usually look transparent.
And after the glass breaks, it will appear as numerous uneven surfaces. When light touches these irregular surfaces, it is reflected and scattered in all directions. This is the same for snowflakes. Snowflakes are made up of hundreds of tiny ice crystals with different shapes and structures, and their surfaces are also irregular.
Since light that touches broken glass or snowflakes is reflected evenly, these rays contain all wavelengths of visible light, including red, orange, yellow, green, blue, indigo, and violet, and together they appear white. This is why we see snow as white.
However, snow can take on other colors under the influence of certain factors. For example, a pink, watermelon-flavored snow called “watermelon snow” may occur in summer in high mountain or polar regions around the world.
Scientists have found that the red color of “watermelon snow” is caused by a green algae called polar snow algae (chlamydomonas nivalis).
This green algae contains a red carotenoid, which can protect it from the sun’s ultraviolet rays, will also absorb heat, and in the surrounding snow melting to provide water to the green algae use.
When the polar snow algae grows out of the surface of the snow, it forms a pink patch, just like pink snow.
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