In art, color is very important. The color wheel is often used to explain the relationship of different colors to one another. In this way, artists know what colors look good with each other, and how to mix paint to produce more colors. All possible color combinations can be made by mixing just three primary colors with white and black. Artists use a color wheel that has the three primary colors - red, yellow, and blue - and three secondary colors - orange, green, and violet - as well as the tertiary colors that are in between, such as blue-green.
In this project, see the bright colors of the rainbow disappear right before your eyes as you learn about the properties of light and how we see color.
2 white paper plates
Cereal bowl or coffee can lid
Thumbtack or pin
Red, yellow, and blue paint*
Glass of water
* Use watercolor in a tube, wet or dry tempera, or any kind of acrylic paint for this project. If using watercolor, choose colors marked with true red, yellow, and blue, or cadmium yellow, cadmium red, and ultramarine or cobalt blue. These colors will allow you to mix every color of the rainbow. If using acrylic or tempera, select very bright primary colors.
Use the cereal bowl or plastic lid to trace a circle onto one of the paper plates, then cut it out with scissors.
Using the protractor, draw seven equal sections onto the circle. This part is tricky! First find the center of the circle and draw a dot there. Then draw a straight line from the center to the edge of the circle. Next, align the straight edge of the protractor with the line you just drew, placing the end of the protractor right on the center of your circle. On the curved edge of the protractor, look for a number that is close to 52 degrees, and mark it with a dot. It doesn't have to be exact, but make it as close as you can. Now, use the straight edge of the protractor to draw a straight line from the center dot to the dot you just made, going to the edge of the paper circle. The angle you drew is 1/7 of the circle! Continue doing this until you have measured all of the sections. (Each section should be about 52 degrees, since a complete rotation around any circle is 360 degrees, and this circle needs to be divided into seven parts. 360/7= 51.4).
Now, mix the paint to create every color of the rainbow: red, orange, yellow, green, blue, indigo, and violet. Use the second paper plate as a palette for mixing colors. Start with quarter-sized blobs of red, yellow, and blue paint, and add more as you need it. You might need to use a little water to thin the paints to get even consistency. Wash your brush by swirling it in the cup of water every time you switch colors. You may need to change the water in the cup after a while.
To make green, mix equal parts yellow and blue. To make the green a bit darker, add more blue and to make it lighter add a little yellow. Orange is made by mixing equal parts of red and yellow. If you want a darker orange, add more red. Violet (purple) is made of equal parts red and blue. The last color you will need is indigo, which is a sort of dark, bluish purple. Add equal parts of purple and blue to make indigo.
Now that you have mixed the paint you need, paint the sections in order from red to violet. While painting, dip your brush in the water often to keep the paint smooth and even in consistency. Once you have finished painting, let your color wheel dry for a few hours.
Using a thumbtack and pair of scissors, make a hole in the center of your color wheel big enough for a pencil to fit through.
Push the pencil through the hole, and spin it quickly (on a table) to watch the colors disappear!
Light is made of all the colors in the rainbow. When it hits a colored object, most of it is absorbed and only one color is reflected. A red object, for example, absorbs almost the full spectrum of light, reflecting red only.
Our eye is able to see because of light-sensitive photoreceptor cells called rods and cones that are in the retina, or layer of tissue in the back of the eye. Rods and cones sense the different light waves reflected off surfaces, then send signals to the brain. If no light is reflected, but all colors are absorbed, that surface will look black. If no light is absorbed, the object will look white.
When the color wheel was spinning, the colors changed faster than the photoreceptors could communicate with the brain, so the reflection of the colors blended and you saw white light!
Colored Light = White?
Artists mix the primary colors of red, yellow, and blue, but scientists use a different set of primary colors when talking about the visible light spectrum: red, green, and blue. These colors can be used to explain how the entire spectrum of colors mixed together makes white light. To see how this works, experiment with three flashlights and red, blue, and green cellophane. Attach a different color of cellophane to each of the flashlights with a rubber band. You may need someone to help you shine all of the flashlights onto a plain white surface such as a wall, sheet, or poster board. Position the green flashlight so that it is shining directly onto the white surface, and hold the blue light below it, at an equal distance away from the white surface, so that it overlaps the area that the green flashlight is shining on. Then hold the red flashlight above the green one, at an angle so that it lights up the same area as the green and blue lights are shining on.
A bright white light should appear on the surface where the colors overlap. You may need to adjust the flashlights a little bit for this to happen. Try sticking your hand between the surface and the colored lights. How many different colors do you see? All of those colors are created by the three primary additive colors.