Adding colors
Look at your computer screen with a strong magnifying lens (there's one in your kit -- use the small lens on the handle). You will see that the picture is made up of tiny colored dots. How many different colors of dots are there? Make a table showing how the screen makes some of the different colors in the panel below.  There are surprisingly few colors used to make the different bands below.

This effect is called color addition: we are combining lights of only a few different colors to make our mind think it is seeing all colors. It is a very different kind of combining than was involved in the "color subtraction" activity. So if someone asks, "What is red plus green?", the answer depends on whether it is colors of light (like the little colored dots adding up to make the pictures above) or colors of filters that are being stacked together and put in front of a light or a colored object.


Color Addition Color Subtraction
Mixing red light, blue light, and green light
-- pretend these are colored spotlights		 Combining an aqua filter, a yellow filter,
and a magenta filter
--pretend we are viewing white light
through overlapped filters.

Box:  
Adding and subtracting colors

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Copyright 2000 J. P. Straley and S. S. Kovash