Huygens' principle may reveal interaction between light and atoms

We used Huygens' principle to study the interaction between light and atom, and revealed the microcosmic process of the attenuation and gain of a plane wave. We began with the shadow of a leaf, expanding to the atomic absorption plane wave, and obtained the expression of the atomic absorption photon by using Huygens' principle. Also the method of negative absorption is used to analyze the optical gain process, and we obtained the properties of a stimulated radiation photon according to the fact that the optical gain is atomic collective contribution of the stimulated radiation, the result shows that the atomic stimulated radiation is not photons cloning.