Abstract: 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 has attracted a number of experimental researches, is necessary for the description of light. It is shown 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.

Key words: the nature of light, quantization of light energy, classical electromagnetic theory, consid-eration of statistics