WHAT MAKES THE SNOW WHITE?

We’re all used to seeing white snow, but have you ever wondered why it’s so white and opaque?

Why is snow white if water and ice are both transparent? Water, in its purest form, is colorless, as most of us are aware. Impurities in water, such as mud in a river, allow water to acquire additional nuances.

In the case of snow, depending on the conditions, it can also take on other colors. As a result, when snow is compacted, it can acquire a blue hue, which is very common in glacier blue ice. However, white and blue are not the only colors of snow and ice. Algae can grow in snow, turning it red, orange, or even green. We’ll remember reading about “watermelon snow,” which is caused by a type of cold-loving algae that lives inside the layer of snow, coloring the snow with this unusual tincture.

Impurities in the snow, such as the example we discussed earlier, will cause it to appear a different color, such as yellow (I think it is no surprise to anyone to see yellow snow; if you see it, be sure that there are animal tracks nearby) or brown. The presence of dirt and debris near a road can cause the snow to appear gray or even black.

Where do you get your unique color?

Regardless of these variations, the most well-known feature of snow is its pale color. Where does it get its whiteness?

We must keep in mind that visible light is made up of many different light frequencies. Colors are perceived by our eyes as a result of these frequencies. Objects differ in color because the particles that make up the object vibrate at different frequencies. When it comes to light energy, molecules and atoms absorb a certain amount of energy based on the frequency of the light and then emit this absorbed energy as heat. This means that some objects absorb more light at certain frequencies than others.

So, if the snow is clear, why is it colored? Understanding the physical properties of snow and ice aids in our understanding of snow color. It turns out that the ice is translucent rather than transparent, which means that photons of light do not pass directly through the material; rather, the particles of the object change the direction of light. As a result, the photon of light’s trajectory changes and it exits the ice in a different direction than it entered. Given that snow is nothing more than a jumble of tiny ice crystals of varying shape and structure joined together, when a photon of light enters a layer of snow, it passes through an ice crystal at the top, slightly changing direction, and sending it to another ice crystal, which does the same.

In essence, all ice crystals reflect light in all directions. It does the same thing with all light frequencies (red, orange, yellow, green, blue, indigo, and violet), and the “color” of all frequencies combined in the visible spectrum gives us the color white, which is what we see in snow. That is why, when we look at snow, our eyes “see” white because some of the light that hits the snow is distributed evenly across all spectral colors, and because white light is made up of all the colors of the visible spectrum, we see white snowflakes.

Nobody, however, sees a single snowflake at a time. Normally, millions of snowflakes cover the ground. There are so many places for light to reflect when it hits snow on the ground that no single wavelength is constantly absorbed or reflected.

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Gerardo Franco is a science communicator, with studies at the Georgia Institute of Technology.

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Gerardo Franco

Gerardo Franco

Gerardo Franco is a science communicator, with studies at the Georgia Institute of Technology.

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