Dual Nature of Light

By the early twentieth century, it became clear that light cannot be described completely by either the pure-particle or the pure-wave picture alone -- it genuinely has a DUAL nature, behaving like a wave in some experiments (interference, diffraction, polarization -- the subjects of this chapter) and like a stream of discrete particles, called PHOTONS, in others (particularly experiments involving the exchange of energy between light and matter, such as the photoelectric effect). Which aspect of light's nature is revealed depends entirely on the kind of experiment being performed; this dual wave-particle picture of light -- and of …