Have you ever heard that white light is made up of all the different kinds of light? And maybe you’ve wondered how we actually see colors? This month we’ll discover how light behaves as it makes its way to your eyes.
One sheet of white paper, a tissue, oil (vegetable, olive, it doesn’t matter)
Hold a piece of paper up to the light, blocking your view of the light. Observe the back side of the paper. Notice how dark it appears?
Now hold the paper down in front of you so the light shines right on the surface. Notice the difference from step one? It is a lot brighter.
Next put a dab of oil on the center of the paper with the tissue.
Repeat steps one and two, watching how the light changes appearance as you shift the paper .
When you hold the paper up to the light, you should notice it is dark. And rightly so, it is blocking the light! The other side is appearing lighter because the light it bouncing off of it away from your eyes. All the light is going the other way! When you put the paper down and look at the light on it, it appears white because this time the reflecting light bounces into your eyes.
What does the oil do to change all this?
When you hold it up to the light you should see a tiny circle of light surrounded by darkness. Why? The oil allows the light to come through and make it to your eyes while the rest of the paper without oil reflects the light away. Flip the paper down and the opposite happens! The oil spot appears dark this time and the paper is bright. All the light is going through the paper now at that one spot, making it appear dark. The rest of the paper is still reflecting light to your eyes.
How does this work with different colored paper? Or even different thicknesses of paper? Try them out and see! Take all your learning from this lesson and describe how sunglasses work.
Steve Davala is a high school chemistry teacher who likes to write. He’s got two kids of his own and subjects them to these science activities as guinea pigs.