ABSTRACT
Energy radiates from one object to another one under all conditions and all times. The source of the emitted radiation is a combination of electronic and molecular oscillations and transitions in the emitting material, as well as lattice vibrations. Once the energy is radiated, it propagates as an electromagnetic (EM) wave, regardless of whether there is vacuum or matter along its path. After these waves reach another object, they partially lose their energy and give rise to electronic or molecular transitions and/or lattice vibrations in the receiving body. This is called absorption, which causes the energy level of the second object to rise. Both the emitted and absorbed radiation are functions of the physical and chemical properties of the material as well as its energy level (as quanti¢ed by its temperature). The interaction between emitting and absorbing bodies via EM waves is the essence of radiative energy transfer.
