Dualism Between Wave and Particle, Preview of Quantum Theory, and Elementary Particles

In the previous chapter we considered the concept of particles. This chapter we begin by introducing a number of basic concepts, which are essential for an understanding of wave phenomena in all parts of physics. We then will discuss the relation between waves and particles, which has played an important role in the development of modern physics. In 1925, Werner Heisenberg formulated his matrix mechanics. This is a quantum mechanics, which is derived from classical mechanics by introducing particle quantization. This theory has already been discussed in Section 58.21. Independently, in 1926, Erwin Schrödinger formulated an equivalent wave mechanics which is derived from wave quantization. The main objective of this chapter is to present a survey. This, together with the previous chapter, might help the reader to better understand many of the problems discussed later on. We thereby follow the fascinating line of development, which leads to the central problem of modern physics—the creation of a unified theory for all four interactions in nature. Quantum theory will be discussed in greater detail in Part V. Only a minimal program is presented here. Some interesting problems that we consider are: (i) Spectrum of the hydrogen atom. (ii) Quantum mechanical treatment of the harmonic oscillator in the context of Schrödinger’s wave mechanics. (iii) Functional analytical deduction of Heisenberg’s uncertainty relation.