  The paper shows the relationship between the major wave equations in quantum
mechanics and electromagnetism, such as Schroedinger's equation, Dirac's
equation and the Maxwell equations. It is shown that they can be derived in a
striking simple way from a common root. This root is the relativistic
fourvector formulation of the momentum conservation law. This is shown to be a
more attractive starting-point than Einstein's energy relationship for moving
particles, which is commonly used for the purpose. The theory developed gives a
new interpretation for the origin of antiparticles.
