ABSTRACT
The challenge facing Isaac Newton was to get all his optics experiments, carried out in the late 1600s, to agree with his particle theory. To explain how light moves through optical devices with lenses such as microscopes, telescopes, and eyeglasses, a simple ray-tracing model of the light particles suffices. Christiaan Huygens was a Dutch scientist who had a radically different theory of light that he called wavelets. His theory was the competing theory to Newton’s particles. While a bit more challenging to deal with mathematically, it too was able to explain polarization and the separation of the rainbow into colors and the opening angle of the smaller primary rainbow, but it also had problems with the sizeable secondary bow with its reversed colors, the intervening Alexander’s dark band, and the bane of Icelandic spar.
