Gummy bears are a great way to bust one of the common misconceptions about light reflection. The misconception is this: most students think that color is a property of matter, for example if I place shiny red apple of a sheet of paper in the sun, you’ll see a red glow on the paper around the apple.
Where did the red light come from? Did the apple add color to the otherwise clear sunlight? No. That’s the problem. Well, actually that’s the idea that leads to big problems later on down the road. So let’s get this idea straightened out.
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Materials:
- flashlight
- laser
- red and green gummy bear
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It’s really hard to understand that when you see a red apple, what’s really happening is that most of the wavelengths that make up white light (the rainbow, remember?) are absorbed by the apple, and only the red one is reflected. That’s why the apple is red.
When the light hits something, it gets absorbed and either converted to heat, reflected back like on a mirror, or transmitted through like through a window.
When you shine your flashlight light through the red gummy bear, the red gummy is acting like a filter and only allowing red light to pass through, and it absorbs all the other colors. The light coming from out the back end of the gummy bear is monochromatic, but it’s not coherent, not all lined up or in synch with each other. What happens if you shine your flashlight through a green gummy bear? Which color is being absorbed or not absorbed now?
Now remember, the gummy bear does NOT color the light, since white light is made up of all visible colors, red and green light were already in there. The red gummy bear only let red through and absorbed the rest. The green gummy bear let green through and absorbed the rest.
Now…take out your laser. There’s only one color in your laser, right? Shine your laser at your gummy bears. Which gummy bear blocks the light, and which lets it pass through? Why is that? I’ll give you one minute to experiment with your gummy bears and your lasers.
In the image above, the two on the left are green gummy bears, and the two on the right are red gummy bears. The black thing is a laser. The dot on the black laser tells you what color the laser light is, so the laser on the far left is a red laser shining on a green gummy bear. Do you see how the light is really visible out the back end of the gummy bear in only two of the pictures? What does that tell you about light and how it gets transmitted through an object?
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Interesting results! What colors did you see?
My theory would be that the more hardened part of the jelly beans have hardened sugar crystals, which are refracting and reflecting the light. The gummy center of the jelly beans act as a filter (like the gummy bears), so some light is passing through and some is being absorbed. So you are most likely seeing a combination of light effects.
so we tried this with gummy bears and jellybeans. and the yellow and orange jellybeans had an unexpected special effect!! they looked sort of like the tv fuzz that you get when there is no tv service. just wondering if there is an explanation for that that might apply to light? or chemistry? (like from a certain ingredient or something?)