ABSTRACT
Visible light is a type of electromagnetic radiation whose wavelength lies in a relatively narrow
band extending from about 400 to 700 nm. The area of physics that is devoted to the study of light
is known as optics. This chapter is concerned with those optical phenomena that depend explicitly
on the ultimate wave nature of light, and cannot be accounted for using the well-known laws of
geometric optics. (See Section 7.8.) The branch of optics that deals with such phenomena is called
wave optics. The two most important physical phenomena that are encountered in wave optics are
interference and diffraction. Interference occurs when beams of light from multiple sources (but
with similar frequencies), or multiple beams from the same source, intersect one another. Diffraction
takes place, for instance, when a single beam of light passes through an opening in an opaque
screen whose spatial extent is comparable to the wavelength of the light. Actually, interference and
diffraction depend on the same underlying physics, and the distinction that is conventionally made
between them is somewhat arbitrary.
