Since snow is frozen water, and we all know that frozen water, free of impurities, is clear, why does snow have a distinctive color? To understand this, we need to look at a 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; rather 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 comprised of a 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, the crystals bounce the light all around so that the light comes right back out of the snow pile. Snow 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, even though white isn’t the color we “see” in the individual ice crystals that form snow.
And yes, snow can look blueish-white or pinkish-white depending on how the sun hits it or if it’s in shadow (or yellow if the neighborhood dog happens upon it), as the National Center for Atmospheric Research reminds us. Snow can also be red when it’s full of algae.
Originally Published: Nov 30, 2000