Written by Dr. Claes Johnson | 27 January 2011

All these fifty years of conscious brooding have brought me no nearer to the answer to the question, ‘‘What are light quanta?’’. Nowadays every Tom, Dick and Harry thinks he knows it, but he is mistaken. (Einstein 1954)

1.1    Wave-Particle Duality and Modern Physics
Maxwell’s equations represent a culmination of classical mathematical physics by offering a compact mathematical formulation of all of elec- tromagnetics including the propagation of light and radiation, as electro- magnetic waves. But like in a Greek tragedy, the success of Maxwell’s equations prepared for the collapse of classical mathematical physics and the rise of modern physics based on a concept wave-particle duality with a resurrection of Newton’s old idea of light as a stream of light particles or photons, in its modern version combined with statistics.