A student asked me a question that I couldn't answer. When I pick up the
black pen on my Smart Board, I can write with a really black color --- much
blacker than the appearance of the screen with no illumination at all.
Where does the black come from? I can produce most all the other possible
colors with a combination of the primary colors of light, but if I add all
the colors of light together, it seems like I should get white, not black.
Any help?