Hi! I try to get some intuitive understanding on the equipartition theorem stating that in thermal equilibrium, energy is evenly distributed among all degrees of freedom of a physical system. This is indeed intuitive for a system consisting of composite particles with translational and rotational motion: each degree of freedom is just a kind of velocity, and with the randomness of thermal equilibrium it is intuitive that the energy is distributed equally among the different velocities. By reference to the ideal gass law, this amount should be ##1/2 k T##. However, what about electromagnetic waves: it is intuitive that the energy should be distributed equally amongst the polarizations -- however, why is the energy, also here, ##1/2 kT##? Is it intuitive that the energy associated to a degree of freedom of a material particle is the same as the energy corresponding to degree of freedom of an electromagnetic wave? I.e. ##1/2 k T##?