What it shows:
All colors can be created from a combination of the three primary colors of red, green and blue. The secondary colors of cyan, magenta and yellow are created from a combination of two primaries, and white light is perceived from the combination of all three.
How it works:
The human eye perceives color using three types of receptor whose sensitivities peak in the red, green and blue regions of the spectrum. Other colors are recognized by stimulating more than one type of receptor to a varying degree. Because of this, all colors can be perceived by different combinations of the three primary colors (this is the principal of color TV, as the TV Color Perception demo shows). In this demo, the three primary colors are projected onto a screen and overlapped (figure 1). Where two primaries overlap, a secondary color is created. Equal intensities of red, green and blue creates white light.
figure 1. Colors produced by mixing red, green and blue light
Setting it up:
The three primary color slides are backed with aluminum foil with 1cm diameter holes to give the circular pattern on the screen. Each slide is mounted in a slide projector and angled at the screen so that the overlap as shown in figure 1 is obtained.
Our slides are manufactured by Sergent-Welch (3662). Choosing any set of RGB filters could cause problems with color and intensity balancing in trying to obtain a pure white.