The term radiation broadly applied to a class of physical phenomena that share a characteristic loss of energy in the radiating body or system that results in a propagation of particles and/or waves that carry the ability to do work and thus change the energy state of an impacted body or system.

Radiation is a catch-all name given to several different types of energetic phenomena. In particular, we think of the entire electromagnetic spectrum as being radiation of graduating wavelengths. Heat and visible light, being parts of the spectrum, were among the first forms of electromagnetic radiation recognized by scientists. Electromagnetic radiation is now understood to encompass a broad spectrum of electromagnetic radiation form gamma rays to radio waves that differ only in wavelength and frequency.

Radiation also aptly describes phenomena specifically related to blackbodies that are described by Planck's law, Kirchhoff's law, Wien's law, and the...