The Wave–Particle Nature of Light

Light behaves like a wave or a particle. Various terms are used to describe the luminous phenomena found in nature: light, electromagnetic waves or photons. A mathematical description of light in wave optics theory requires that the associated wave function be a solution to the propagation equation. The wave propagation equation is usually valid for describing a monochromatic wave. The Maxwell equations show that light is a transverse electromagnetic wave, which can be split in two linearly independent components corresponding to light polarization. In the quantum mechanics (QM) theory, the electromagnetic field is quantized as a sum of independent harmonic oscillators. Quantum electrodynamics (QED) theory is applied to describe the electromagnetic interactions between charged particles and an electromagnetic field. Using the Coulomb gauge, the electromagnetic field is expressed as a sum of independent oscillators. In the classical approach, the electromagnetic field is completely defined by its amplitude and phase.