The emission of a photon by an atom in the presence of electromagnetic radiation. The atom can become excited by the absorption of a photon of the right energy and, having become excited, the atom can emit a photon. The rate of absorption is equal to the rate of induced emission, both rates being proportional to the density of photons of the electromagnetic radiation. The relation between induced emission and spontaneous emission is given by the Einstein coefficients. The process of induced emission is essential for the operation of lasers and masers. See also quantum theory of radiation.