Abstract
The mathematical structures of the theories of a two-level atom interacting with radiation and an electromagnetic wave interacting with a dielectric medium in which it is propagated as a plane wave are identical. The spin structure of the Jones operator in optics representing the polarizer, is obtained in its general form in terms of Stokes parameters and identified with the optical density operator with a spin structure identical with the density operator in the quantum mechanics of the atom. While the quantum dynamical equation of the atom can be reduced to the gyroscopic form, the correspondence law giving expression to the parallelism of the two processes leads to forms of the dynamical law in topics which are identical with those of the quantum theory of the atom.