2 Historical Development
The nature of light has interested man since the earliest times. It was thought since ancient times that light was composed of a stream of particles or corpuscles. This was known as the Corpuscular Theory because it helped to explain the rectilinear propagation of light and why shadows were produced from opaque objects. But this theory could not explain correctly the phenomena of refraction, interference, and diffraction that were noted in the seventeenth century. In 1678, a Dutch physicist, Christiaan Huygens, put forth a theory of light that offered an explanation.
He proposed that light was composed of waves and wavelets. Huygens’ theory assumed that light started out as a wavefront in the form of a plane ...