English: Animation of waves emitted by an isotropic radiator, a coherent point source of radiation, represented by red dot. An isotropic radiator emits equal radiated power density in all directions in space. Isotropic sources are mathematical idealizations of real sources, used in optics, electromagnetics and acoustics. The amplitude of the waves is represented by lightness. As they travel away from the source, the waves decline in amplitude by the inverse of distance 1/r and in power by the inverse distance squared 1/r², shown by the declining contrast of the wavefronts. This diagram only shows the waves in one plane through the source; actual isotropic sources would emit waves in three dimensions in space. 240x240 animated GIF consisting of 8 frames looped which repeats every 0.4 sec.