Angular momentum of a circularly polarized light beam.

It is shown that the Maxwell electrodynamics cannot explain the existence of an angular momentum flux in a circularly polarized light beam which has no the phase structure. The fact is that such a beam contains a small rotating electromagnetic mass and, accordingly, contains an angular momentum directed along the beam axis, but this rotating mass has no speed in the direction of the beam axis. Therefore, this angular momentum is not transferred along the beam axis, and there is no flow of this angular momentum along the beam axis. We show the angular momentum flux in such a beam is contained in the main mass of the beam, which does not rotate. This angular momentum flux is a spin flux and is described by the spin tensor. Likewise, taking spin into account is required to explain the classical Beth experiment and other experiments.