  It is currently believed that light quantum or the quantization of light
energy is beyond classical physics and the picture of wave-particle duality,
which was criticized by Einstein but attracted a number of experimental
researches, is necessary for the description of light. We show in this paper,
however, that the quantization of light energy in vacuum, which is the same as
that in quantum electrodynamics, can be derived directly from the classical
electromagnetic theory through the consideration of statistics based on
classical physics. Therefore, the quantization of energy is an intrinsic
property of light as a classical electromagnetic wave and has no need of being
related to particles.
