A triangular solid piece of glass, on which if a ray of light be cast
it will be distinctly divided into the seven colors we see in a
rainbow. By this fact we see that white light is composed of different
rays which have different reflective susceptibilities.


What is a Spectrum?

It is this beautiful band of seven colors obtained by the refraction
of a ray of light through the prism.


Whence come the colors in the objects we see in nature?

They all come from light; every object has a power to absorb certain
rays and to reflect others. A red cloth, for example, absorbs all the
other colored rays except red, and this it gives off, thus appearing
red.


Why are the leaves of plants green?

Because a peculiar chemical substance called chlorophyl, formed within
their cells, absorbs all other rays of light, reflecting only blue and
yellow--which mixture produces the different green tints.


What is Photography?