What occurs during stimulated emission within an active medium?

In stimulated emission, an atom that is in an excited state, having absorbed energy, interacts with incoming photons. When a photon of a specific energy collides with the excited atom, it can stimulate the atom to release a photon of the same energy, wavelength, and phase. This process leads to the emission of a photon while the excited atom returns to a lower energy state or its ground state. This is crucial in the context of lasers, where the produced coherent light is due to a chain reaction of stimulated emissions that amplify the light.

The nature of this process is fundamental to understanding how light amplification occurs in various technologies, particularly lasers. The emitted photon is coherent with the stimulating photon, leading to a cascade effect that enhances the overall light output.

Other options do not accurately describe stimulated emission because they either refer to phenomena that do not involve the interaction of photons in the way described or inaccurately represent the behavior of atoms in this context. For instance, the option discussing electron ejection pertains more to ionization, while the one stating that photons are absorbed without displacement refers to absorption rather than emission processes.