February Kids’ Corner
from the Gale River Cooperative Preschool
Why Is Snow White?
A white blanket of snow is an important part of winter in New Hampshire. But have you ever wondered why snow is white? It’s an interesting question to think about! Snow is made of water. Water is clear. When water freezes to ice, it’s still clear, or at least translucent (which means that light can pass through but it is scattered so you can’t see details clearly). So why, then, is snow white instead of clear or partially clear (translucent)?
Stop and think about or discuss your answer before reading any further!
Snowflakes are tiny ice crystals. If you observe individual snowflakes, you’ll notice that they are translucent like ice. But when you add millions of snowflakes together, you get white! That’s because the millions of snowflakes are bouncing the sunlight around like crazy, and reflecting the light back to your eyes.
To understand why snow is white we need to talk about visible light. Visible light is the part of the sun’s energy that we can see. We divide visible light up into the colors of the rainbow; red, orange, yellow, green, blue, indigo, and violet. All the colors together make up what we call white light.
Certain materials called prisms can separate white light into the colors of the rainbow. Water droplets can act as a prism, which is why we often see rainbows in the sky after a storm.
Have you ever noticed a rainbow in the mist from a sprinkler, or a piece of glass or other material? What you’re seeing is white light being separated out into all its colors!
Since all the colors of the rainbow together make white light, this means that snow is reflecting all the colors of the rainbow back to our eyes. When white light from the sun hits millions of snowflakes, it can’t pass through them all like it can through a layer of ice. Instead, it gets bounced around between the snowflakes, and all the colors (red, orange, yellow, green, blue, indigo, and violet) come back to our eyes, making snow look white.
Not all objects are white like snow, of course. Objects are different colors because they reflect different parts of white light back to our eyes. A green clover, for example, is green because it’s reflecting the green part of white light back to our eyes. When white light hits a clover red, orange, yellow, blue, indigo, and violet light is absorbed, and green is reflected back. Oranges are orange because they’re reflecting orange back to our eyes and absorbing the other colors. Red roses are red because they’re reflecting red back to our eyes. Black objects absorb all colors of visible light (that’s why black clothes get so hot in the sun).
S t r e t c h your knowledge!
We think of green as the color of photosynthesis; the process by which green plants use energy from the sun to make their own food. In light of what you just learned, which color do you think green plants actually use the least for photosynthesis?
Answer: It’s green! Green leaves are using the energy from green light the least in photosynthesis, so the green is what bounces back to our eyes!
Your Turn!
You’ll need:
- A bowl or other clear container
- Snow
Grab a clear container, fill it with snow, and bring it inside. Note that you can’t see through the snow because the many snowflakes packed together are preventing visible light from passing through. Instead, white light is reflected back to you.
Let the snow melt. Notice that now you can see through it…it’s water. Nothing has changed about the snow other than the change from a solid to a liquid, but the way the light passes through is very different.
Now put your container outside and let the water freeze. When it’s fully frozen, note how the light passes through the ice. The clarity of ice will vary depending on several factors including how it freezes, how many air bubbles are in the water, and impurities. What can you observe about the way light passes through your container of ice?
Image sources (in order of appearance)
https://upload.wikimedia.org/wikipedia/commons/7/75/Forest_road_Slavne_2017_G8.jpg
https://upload.wikimedia.org/wikipedia/commons/c/c2/SnowflakesWilsonBentley.jpg
https://upload.wikimedia.org/wikipedia/commons/4/4a/Rainbow_after_thunderstorm.jpg
https://upload.wikimedia.org/wikipedia/commons/f/fa/Prism_flat_rainbow_%28cropped%29.jpg
https://upload.wikimedia.org/wikipedia/commons/6/61/2020_year._Herbarium._Clover._img-009.jpg
https://upload.wikimedia.org/wikipedia/commons/c/c4/Orange-Fruit-Pieces.jpg
https://upload.wikimedia.org/wikipedia/commons/a/ad/Knock-Out-OriginalIMG_3830_Edit.jpg
