Science Smarts: Why is snow white?

By PATTY ROOKS on November 19, 2022.

Please do not hate me, but I have to be honest with all of you, I am quite enjoying the snow we are getting.

Do not misunderstand, I am not fond of the extreme cold, but seeing the snow outside really puts me in a much more festive mood as it makes me think about the approaching Holiday season! Since it has been snowing quite a bit lately, of course, it makes me think…why is snow white? Water is clear, and snow is essentially frozen water, so what is going on here?

Let’s get started!

Materials

• Three flashlights

• Blue, red and green coloured cellophane (you can get this in the gift wrapping section; it is often used to wrap baskets)

• Large sheet of white poster paper

• Rubber bands or string

• Scissors

• Ruler

• Marker

• Dark room

• Science helper

Procedure

1. In a dark room, hang the piece of white poster paper on a clear wall.

2. Using the ruler, measure and then cut a 5 cm x 5 cm square from each of the blue, red and green pieces of coloured cellophane.

3. Take the red piece of cellophane and put it over the bulb end of the flashlight.

4. Secure it with a rubber band or string.

5.Repeat Steps 3 and 4 with the green and blue pieces of cellophane.

6. Have your science helper shut the lights off.

7. Shine the flashlight with the red cellophane on it against the white paper in the room.

8. Observe. What do you see?

9. Shine the flashlight with the green cellophane on it just so it is overlapping one edge of the red circle on the wall.

10. What colour do you see now?

11. Due to you only having two hands, this is where your science helper will come in handy – have your helper shine the flashlight with the blue cellophane just so it overlaps the red and green circles of light. Be patient, sometimes we are not very steady and it may take a couple of attempts.

12. What do you see now?

What is going on?

When the red light shines on the wall, you only see red light. Adding the blue light made it purple. Of course, when you add the blue and green light, you see a turquoise colour and so on. The “magic” appeared when you allowed ALL three colours to overlap – it was actually white! This is because red, green and blue are all additive primary colours.

I know that you are asking what does this have to do with snow? First of all, ice is not really transparent – it bends light (also known as refraction). The ice is acting like a prism, separating all of the colours out, but at the same time, blending them together to create the white colour similar to how we created white in our experiment. Since snow is made up of many ice crystals it actually acts like a prism, bending all of the colours, blending them and creating what we see as white snow! Who knew it was so complicated?!

Patty Rooks, Senior Scientific Consultant PRAXIS, “Connecting Science To The Community”. Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. Address: #12 826 11 Street S. E., Medicine Hat, Alberta, T1A 1T7 Phone: 403.527.5365, email: praxis@praxismh.ca.

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