ABSTRACT
In order to understand the properties of nanoparticles, it is very much required to have knowledge of quantum mechanics. This chapter introduces the basic concept of quantum mechanics. This chapter starts with quantum theory for radiation. It has been observed that the phenomena related to intense radiation like interference, diffraction, etc., could be well described with the help of Maxwell’s wave theory. But in the case of weakly intensed light, wave theory cannot be used to predict the related experimental phenomena. In this regard, quantum theory has been developed considering the particle nature of radiation. This evaluation of quantum theory has been briefly discussed in this chapter. In the world of matter, Newton’s law is successfully used to predict the position, velocity, acceleration, etc., of any macroscopic particle. But this couldn’t be used for particles of tiny dimensions like electrons, neutrons, etc. The difference is that for macroscopic particles we can measure their position and velocity with some accuracy, but for tiny particles, called quantum particles, it is difficult to determine their position and velocity at any given point in time. Wave theory has been presented by Schrödinger to predict features of quantum particles. We have given a few examples where Schrödinger’s wave theory can successfully explain quantum particles’ behavior under static as well as dynamic conditions. But in a real system, we cannot use this theory. We have discussed a few approximation methods to be used with Schrödinger’s wave theory in the case of a real system.
