The Nature of Light
In general, optical phenomena can be considered from three different points of
view. Geometric is the straightforward view that is the easiest to visualize,
interpreting light in the form of rays, and describes the rules that determine how
light propagates and how optical images are formed. However, it does not
describe the interaction of light and matter. In wave optics light is interpreted
as periodic oscillations of electric and magnetic fields in time and space(Figure
2.1). Building on this concept as first described by Faraday (1831), in 1864 the
English physicist James Clark Maxwell formulated the basic equations of
electrodynamics, which “reveal the structure of the electromagnetic(light)fields”
(Albert Einstein). In many respects light waves are comparable to mechanical
waves in liquids, although this analogy has its limit. However, only in this
consideration are the phenomena such as refraction, reflection, interference and
polarization “understandable”. In the third point of view, via quantum optics, light
is described as a stream of mass-less particles, known as “photons”. It is only the
quantum optical interpretation that is capable of describing light absorption and
emission as the foundations of optical spectroscopy.