The [Schrödinger equation][1] describes the quantum mechanics of a single massive non-relativistic particle. The [Dirac equation][2] governs a single massive relativistic spin-½ particle. The photon is a massless, relativistic spin-1 particle.

What is the equivalent equation giving the quantum mechanics of a single photon?


  [1]: http://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation
  [2]: http://en.wikipedia.org/wiki/Dirac_equation