Here’s a trick question – can you make the color “yellow” with only red, green, and blue as your color palette? If you’re a scientist, it’s not a problem. But if you’re an artist, you’re in trouble already.
The key is that we would be mixing light, not paint. Mixing the three primary colors of light gives white light. If you took three light bulbs (red, green, and blue) and shined them on the ceiling, you’d see white. And if you could magically un-mix the white colors, you’d get the rainbow (which is exactly what prisms do.)
If you’re thinking yellow should be a primary color – it is a primary color, but only in the artist’s world. Yellow paint is a primary color for painters, but yellow light is actually made from red and green light. (Easy way to remember this: think of Christmas colors – red and green merge to make the yellow star on top of the tree.)
As a painter, you know that when you mix three cups of red, green, and blue paint, you get a muddy brown. But as a scientist, when you mix together three cups of cold light, you get white. If you pass a beam white light through a glass filled with water that’s been dyed red, you’ve now got red light coming out the other side. The glass of red water is your filter. But what happens when you try to mix the different colors together?
The cold light is giving off its own light through a chemical reaction called chemiluminescence, whereas the cups of paint are only reflecting nearby light. It’s like the difference between the sun (which gives off its own light) and the moon (which you see only when sunlight bounces off it to your eyeballs). You can read more about light in our Unit 9: Lesson 1 section.
Here’s what you need:
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You can find disposable test tubes here: https://www.homesciencetools.com/test-tubes-polystyrene-13×100-mm-12-pack
Hi. Where can I buy disposable test tubes?
Yes if they are the kind that have different color fluid inside (usually they aren’t – it’s the same color fluid but they change the outside color of the transparent plastic to get the color indicated on the packaging).
Will the light sticks at a dollar store work? Thanks!
whats with the picure of choclte
this is the awsomest oops thats not a word{says son}
Thank you, it is very interesting. We liked it a lot!
This is SO COOL!! Thanks for sharing it!
We finally got to do this experiment and had a ball. Husband painted this around the house, especially in bedrooms. Looked really cool on the jar after we shook it up with lid on. Ours had bit of red glow where chemical was in bottom of jar. On the walls of the jar it looked a light blue or green. Mostly, it was clear after all colors were mixed. Happy time talking about “cold light”. Thanks
Sure – incandescent bulbs are warm (even hot!) light, as are campfires and street lamps. Most light sources we use are “warm lights”.
Is there warm light?
-Robin368 (Alex’s daughter’s code name)
If you’re an artist, then the three primary colors are as you described. But in the world of light, you make yellow light with red and green light. 🙂 Check out this experiment about this idea.
Why do you use red, blue and GREEN light. . . I thought the primary colors were red, blue and yellow??? ~Jasmin
Hi my name is Anna ( merry’s daughter,) I thought that video was RELLY COOL!!!! I’m somewhat an artist myself, so when my mom told me about this experiment, I didn’t belive her until I saw the video. That’s awsome!!!!
I can’t wait to do it!!!!!! THANK YOU!!!!!!!!!!!!
The simple answer: dilute with water and flush to sewer if local ordinances allow. Otherwise, throw in a container (like an empty trash bag) and take it to your waste facility.
A lot of info on the internet state that glow sticks are made from non-toxic chemicals. Here’s the real deal (from Wiki):
Glow sticks contain hydrogen peroxide, and phenol is produced as a by-product. It is advisable, therefore, to keep the mixture away from skin and to prevent accidental ingestion if the glow stick case splits or breaks. The glow stick contains two chemicals and a suitable fluorescent dye (sensitizer, or fluorophor). The chemicals in the glass vial are a mixture of the dye and diphenyl oxalate. The chemical inside the plastic tube is hydrogen peroxide. By mixing the peroxide with the phenyl oxalate ester, a chemical reaction takes place: the ester is oxidized, yielding two molecules of phenol and one molecule of peroxyacid ester (1,2-dioxetanedione). The peroxyacid decomposes spontaneously to carbon dioxide, releasing energy that excites the dye, which then relaxes by releasing a photon. The wavelength of the photon—the color of the emitted light—depends on the structure of the dye. The decomposition is a reverse [2 + 2] cycloaddition, which is a forbidden transition; so the reaction cannot release its energy as heat, but only as a single photon with an exact energy quantum.
What do we do with the liquid after the experiment is over? Thank you.
This looks so cool. I can NOT wait to try do it.
This is soooo cool! I can’t wait to it do myself…….
Jasmin
Yes – you can get true color glow sticks here.
Can’t wait to do this with the children. Any idea where to get these glow sticks. I can’t think of anywhere at the moment, myself. thanks from Sanders14
This is one of the trickiest parts of understanding light. In the artist world, the three primary colors of paint are red, yellow, and blue.
When you mix light (not paint), you need red, green, and blue.
This small change is a world of difference between mixing paint and mixing light. It’s just the way the universe is wired. I do recommend getting a yellow light stick and seeing what happens when you substitute it for green… 🙂
I’m wondering why we don’t use a yellow light stick instead of green.