Wave equation of single photon

Photon, due to the ‘continuous and periodic action’ about its travel line from the emitting atom hints the ‘continuous and periodic function’ about its travel line and consequently the wave equation. The travel line is one with respect of which the measurements of all length-time observables are done, for instance wavelength, frequency as time inverse etc. It is the continuous and periodic function (or action) of photon that concern the light as electromagnetic wave on single photonic level. Here within this paper the wave equation of single photon is obtained by the consideration of its qubit complex coefficients as function to which the calculus approach ‘differentiation’ applied like to any other ordinary function.