Shown in the photograph below is the platform of an overhead projector, covered on the left with green plastic and on the right with red plastic. Lamentably, you cannot see the color of the light coming out of the lens, so that is the topic for this question.
Suppose that we remove the black baffle covering the projector lens in the photograph. When you look backward into the lens on top of the overhead projector from which the light is emerging,you may see a number of colors. For example, you might see red or green, or perhaps yellow, the color obtained when red and green are mixed. Or you might see blue, produced when red and green are absorbed from the white light produced by the projector.
When you look backward into the lens on top of the overhead projector from which the light is emerging, you will see:
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