ABSTRACT
The creation of quantum mechanics in the period 1924–1928 restored logical consistency to its rightful place in theoretical physics. The study of interaction between light and electrons provided most of the important clues in the development of the quantum theory. This chapter shows that in the interference experiments the statistical distribution of quanta is correctly given by the intensity of the wave field as computed from classical electromagnetic theory. It also shows that under special circumstances the classical theory also makes contact with some of the empirical facts in Compton's experiment. The chapter discusses a famous example due to W. Heisenberg, in which Compton scattered γ-rays are brought to focus by a microscope. It provides the uncertainty relations for the dynamical variables of a particle from the conservation laws and the properties of photons. Because the motion of charged particles can be deduced from their attendant fields, it is clear that fields cannot be measured to arbitrary precision.
