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  • 11/26/2011

Why is Snow White?


Snow can be termed as, “a bunch of ice crystals combined together”‌. Whenever we think of snow, a beautiful picture of purity and decency comes into our mind. A place covered with snow appears like heaven. People love snow because it appears peaceful to the eye. Also the white color is a sign of purity. A general saying is that it’s pure because it’s white. But why the color of snow is so white? The reason is scientific enough to explain.

To understand where the whiteness comes from, we need to back up and look at why different things have different colors in the first pla‌ce. Visible light is made up of many different frequencies of light. Our eyes detect different frequencies as different colors. Different objects have different colors because the particular particles (atoms and molecules) that make up the object have different vibration frequencies. Basically, the electrons of the particle will vibrate a certain amount in response to energy, depending on the frequency of the energy. In the case of light energy, the molecules and atoms absorb a certain amount of light energy depending on the frequency of the light, and then emit this absorbed energy as heat. This means that objects absorb certain frequencies of light more than others.

A couple of different things can happen to the light frequencies that are not absorbed. In some material, when a particle re-emits the photons, they continue to pass through to the next particle. In this case, light travels all the way through the material, so the material is clear. In most solid material, the particles re-emit most of the unabsorbed photons out of the material, so no light, or very little light, passes through and the object is opaque. The color of an opaque object is just the combination of the light energy that the object's particles did not absorb.

So, since snow is frozen water, and we all know that frozen water is clear, why does snow have a distinctive color? To understand this, we need to back up and look at an individual piece of ice. Ice is not transparent; it's actually translucent. This means that the light photons don't pass right through the material in a direct path -- the material's particles change the light's direction. This happens because the distances between some atoms in the ice's molecular structure are close to the height of light wavelengths, which means the light photons will interact with the structures. The result is that the light photon's path is altered and it exits the ice in a different direction than it entered the ice.

Snow is a whole bunch of individual ice crystals arranged together. When a light photon enters a layer of snow, it goes through an ice crystal on the top, which changes its direction slightly and sends it on to a new ice crystal, which does the same thing. Basically, all the crystals bounce the light all around so that it comes right back out of the snow pile. It does the same thing to all the different light frequencies, so all colors of light are bounced back out. The "color" of all the frequencies in the visible spectrum combined in equal measure is white, so this is the color we see in snow, while it's not the color we see in the individual ice crystals that form snow.

In fact snow can also be seen in different instead of white only. During snow formation, the snow crystals may reflect in distinct color. This happens only when air contains colored dust particles in it. This type of snow is generally found in particular areas where air is contained with lots of dust particles, for example- The ‘Sahara Desert’. In Sahara Desert we found red sand that gets mixed up in the air and snow crystals appear reddish in color.




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