Emitting

Emitting refers to the act of sending forth energy, particles, or signals from a source. The term is used across science and engineering to describe processes in which something leaves a system as an output, such as light, heat, chemical vapors, or electrical signals. Emitting is distinct from absorption, in which a system takes in energy or matter.

In physics, emission commonly means the release of quanta as a system relaxes from a higher energy state to a lower one. Photons are emitted by atoms and molecules during electronic transitions; this includes spontaneous emission, where the process occurs without external influence, and stimulated emission, where an external photon induces the transition. Thermal emission, or blackbody radiation, arises from the temperature of an object and spans a broad spectrum depending on temperature.

Specific forms include photoelectric emission (emission of electrons driven by light), field emission (tunneling of electrons in strong electric fields), and radioactive decay, which emits alpha, beta, or gamma radiation. In condensed matter and materials science, acoustic emission describes the release of transient elastic waves during deformation or fracture. Environmental and industrial contexts study the emission of gases, vapors, or pollutants from processes and equipment.

Measurement and practical applications often rely on detecting and analyzing emitted energy. Emission spectroscopy characterizes materials by their spectral lines; LEDs and lasers are engineered emitters that convert electrical energy into light. In computing and communications, emitting is used to describe the generation of events or signals by software or hardware components.

Etymology: emitting derives from emittere, meaning to send forth.