Atmosphere And Weather

Why Snow is White



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"Why Snow is White"
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Why is snow white even though it's made of ice, which usually appears clear? Viewed with common logic, if snow is made of ice, shouldn't it be clear or translucent in appearance? Well, it's because it isn't ice, but a collection of ice crystals.

While the simple fact that snow flakes are made up of a random collection of ice crystals is known, it still adds to the confusion. To clear up the questions; instead of thinking ice, think of light. Visible light, often referred to as "White Light" contains in its wavelength spectrum the colors of the rainbow: Red, Orange, Yellow, Green, Blue, Indigo, and Violet. When an object reflects any particular wavelength our eyes perceive it as that color, while the rest are absorbed. Something colored black is absorbing all the colors, something red is reflecting red and absorbing the rest, while something that's white reflects them all.

Even in knowing the basics of colors, it still doesn't explain why snow is white and ice is translucent. Well normally, when ice forms on the surface of water or an object its crystals form in a uniform direction, allowing light to pass through, strike an object, and bounce back through the ice to the human eye. Because the light is able to return through the ice we perceive it to be without color. Yet, when light tries to pass through the complex formation of a snow flake's ice crystals, the light is reflected off all the surfaces and scatters. Since no wavelengths are absorbed and none pass through, the snow flake appears white.

A similar observation of this can be performed on regular ice as well by shaving or scraping a thin layer off. As the edge of the scraping tool moves along the surface of the ice, the uniform crystals are being compressed, broken, or jumbled in different directions. Because the shaving is no longer consistent of uniform crystals, it reflects the light and appears white.

However, snow isn't always white. White snow occurs when the water in the atmosphere crystallized is pure. At times pollutants or other impurities in the atmosphere can form into the ice crystals, allowing some absorption and redirection of color. In areas of heavy pollution snow takes a grayish color, which is the most typical, but other colors; reds, greens, blues have been seen as well. Depending upon the impurities used the possibilities besides the simple "white" is many.

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