Abstract: The physical essentials of the process that the free electron in empty-lattice model becomes Bloch＇ s electron in crystal under the action of perturbing periodic potential are revealed by analysis from the point of view of wave theory. The result indicates that the propagating plane wave representing the wave function of the free election in empty-lattice model brings about various scattered plane waves everywhere in crystal under the action of perturbing crystalline potential, and it brings about Bloch＇s theorem that these scattered plane waves interfere with each other because of the translational symmetry or periodicity of crystalline structure.

Key words: Bloch＇ s theorem, crystalline potential, scattered plane wave, translational symmetry, interference