You can use colored lightbulbs to demonstrate the mixing of different colors of light. For a description of how to do this well, along with an explanation of the science involved and suggestions for related activities, go to the Exploratorium's Colored Shadows Snack .
You can also demonstrate the mixing of different colors of light with flashlights covered with colored plastic. The Franklin Institute Science Museum's Color of Light activity tells you how to do it.
To demonstrate the mixing of pigment, you can't get much more hands-on than paints and paintbrushes. Give your students magenta, cyan, and yellow tempera paints, and challenge them to create as many colors as possible. If that seems too open-ended, you can give them examples of specific colors that they must try to match. You may want to give them white paint as well, to allow them to change the saturation of the colors that they create. For students who steadfastly maintain that red, blue, and yellow are the primary colors of paint, give them these three colors, and challenge them to make magenta and cyan.
Magic markers in magenta, cyan, and yellow can also be used to demonstrate the mixing of pigments. (We have had luck with Mr. Sketch markers.) However, with paint, it is easier to vary the proportion of each color in the mix, and thus create more colors.
To show students that the images on color TV screens and computer monitors are made up of pixels of red, green, and blue light, you can flick a drop of water onto the screen. The water drop acts as a miniature magnifier, and you can see the individual colors that create the overall color. The Little Shop of Physics has an online activity called Seeing Spots that leads students through this activity and explains the science involved. The Ontario Science Centre has a similar online exhibit called Get the Drop on Pixels that also leads students through this demonstration.
Color addition can also be demonstrated by spinning tops painted with different colors. Go to the Franklin Institute Science Museum's Adding Colors activity for instructions.
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Last update: May 2000
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