It is shown that the relation between ray optics and wave optics is analogous to the relation between the classical mechanics of a point particle and quantum mechanics. The time coordinate of quantum mechanics has to be replaced with a length coordinate and the light wavelength X takes the place of Planck’s constant <i>h</i>. A well-known result of quantum mechanics is that it coincides with classical mechanics in the limit <i>h</i> → 0. Correspondingly, wave and ray optics must coincide in the limit λ → 0.
D. GLOGE and D. MARCUSE, "Formal Quantum Theory of Light Rays," J. Opt. Soc. Am. 59, 1629-1631 (1969)