When you change the wavelength, you change the color of the light. 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?

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Here’s a second video that shows you how to make your own with nail polish and flashlights…

How does that work? Why do you only see certain wavelengths? Here’s a video on the physics behind it…

Click here to go to next lesson on Paint and Light

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