Poynting's theorem
noun
Poyn·ting's theorem
ˈpȯintiŋz-
: a statement in electromagnetic theory: the transfer of energy by an electromagnetic wave is at right angles to both electric and magnetic components of the wave vibration and its rate is proportional to the vector product of their amplitudes
Word History
Etymology
after John H. Poynting †1914 English physicist, its originator