This tutorial begins with the relationship of source-free classical electromagnetism to ultra-relativistic free-photon quantum mechanics. The linear transformation of the source-free classical-electromagnetic real-valued transverse vector potential to its corresponding free-photon Schroedinger-equation complex-valued transverse vector wave function is obtained. It is then pointed out that despite the free-photon Klein-Gordon equation's being formally identical to the source-free classical-electromagnetic vector-potential wave equation, it yields not only free-photon Schroedinger-equation wave functions but also their complex conjugates, which don't satisfy the free-photon Schroedinger equation. This is a consequence of admitting complex-valued solutions of the Klein-Gordon equation -- of course only its real-valued solutions apply to the classical vector potential. It is pointed out that solutions of the free-particle Dirac equation likewise occur in conjugate pairs, and that its Hamiltonian operator implies a variety of unphysical consequences, e.g., any Dirac free particle's speed is that of light times the square root of three.
This paper analyzes the quantities of energy and momentum in the definitional rela-tionship of relativistic mechanics, in the de Broglie momentum hypothesis and in the Klein-Gordon, Dirac and Schrodinger equation. The results of analysis shows that Planck constant and relativistic relationships on the length contraction and increase in mass are a reflection of the same physical principles in nature, that λ designated in the de Broglie hypothesis λ =h/mv as the wave of matter with rest state value λ = ∞ must be connected with a real dimension of a particle with rest state value λ = lo = moc and that on this ba-sis we can come to the fundamental equations of quantum mechanics that are the Klein-Gordon, Dirac and Schrodinger equation without the necessity of the wave functions.