Abstract This article examines models and theories of energy and matter behaviour developed in microscopic experiments of quantum mechanics; the branch of physics relating to the very small, which studies the physical properties of nature at atomic scales and subatomic particles. It is based on the idea that energy, at the sub-atomic level, can only be emitted and absorbed in discrete amounts - small units – called “quanta”. We begin by remembering that the ideas of the philosopher Democritus, on the assumption of a finite division of matter, led to the search for the atom, allowing the development of what is now known as physics. It is particularly discussed how the understanding of electricity made it possible to affirm and discover the nature of the atom, not as Democritus thought, but that its existence as a basic component of matter could be verified. In this text, we make a path of experiments and ideas that led to the current model of the atom, and that allowed the development of a theory about its nature and properties. Finally, conclusions on this brief study are presented.
Abstract This article examines models and theories of energy and matter behaviour developed in microscopic experiments of quantum mechanics; the branch of physics relating to the very small, which studies the physical properties of nature at atomic scales and subatomic particles. It is based on the idea that energy, at the sub-atomic level, can only be emitted and absorbed in discrete amounts - small units – called “quanta”. We begin by remembering that the ideas of the philosopher Democritus, on the assumption of a finite division of matter, led to the search for the atom, allowing the development of what is now known as physics. It is particularly discussed how the understanding of electricity made it possible to affirm and discover the nature of the atom, not as Democritus thought, but that its existence as a basic component of matter could be verified. In this text, we make a path of experiments and ideas that led to the current model of the atom, and that allowed the development of a theory about its nature and properties. Finally, conclusions on this brief study are presented.
Quantum mechanics is the study of matter and radiation at an atomic level. It is a mathematical tool for predicting the behaviours of microscopic particles. This chapter discusses the historical background of quantum theory. Planck's idea of discrete energy of a harmonic oscillator implies that the frequencies for the absorbed and emitted radiation should be discrete. According to classical physics, a system can absorb or emit any amount of energy. In 1902 Phillip Edward Anton Von Lenard, an assistant of Hertz, studied photoelectric effect. His setup consisted of a photocell connected to a circuit with a power supply, voltmeter and micro-ammeter. The Franck–Hertz experiment gave an evidence of discrete energy levels of atoms. The particle nature of radiation is established by the Compton effect. Lasers, semiconductors and superconductors are just few among the various applications of the most radical predictions of quantum mechanics.
The first objective of this chapter is to briefly review some of the basic ideas about the structure of matter, in particular the concepts of microscopic physics, in order to recall the knowledge gained in previous physics (and chemistry) courses and make it more precise. Our review will be very concise, and most statements will be made without any proof or detailed discussion. A second objective is to give a brief description of some of the crucial stages in the early development of quantum physics. We shall not follow the strict historical order of this development or present the arguments used at the beginning of the last century by the founding fathers of quantum mechanics; rather, we shall stress the concepts which we shall find useful later on. Our last objective is to give an elementary introduction to some of the basic ideas, like those of a quantum particle or energy level, that will reappear throughout this text. We shall base our review on the Bohr theory, which provides a simple, though far from convincing, explanation of how energy levels are quantized and how the spectrum of the hydrogen atom arises. This chapter should be reread later on, once the basic ideas of quantum mechanics have been made explicit and illustrated by examples. From the practical point of view, it is possible to skip the general considerations of Sections 1.1 and 1.2 at the first reading and begin with Section 1.3, returning to those two sections later on as needed.
Due to the idea of atomism, there were discovered atoms, nucleons, and electrons. The atomic theory incorporated seeds of the idea of infinite divisibility of matter aimed at perceiving the structure of the entire material world. The next step in that perceiving should have been the recognition of ether discovered in Fizeau’s experiment. However, physicists did not recognize the discovery. The neglect of ether in physical theories resulted in physicists’ failure to use the methods of “classic”, Newtonian physics to gain a detailed understanding of atomic structure, and to build a “classic” microworld theory. As consequence, there emerged the quantum hypothesis that became a basis for the quantum physics of microworld. As the quantum hypothesis appeared to be in irreconcilable contradiction with the idea of infinite divisibility of matter, because of the neglect of ether, the quantum physics failed to understand the real structure of electrons and nucleons, even though all the necessary and ample experimental facts there had been obtained on microobject accelerators. Instead of objective ideas of the structure of electrons and nucleons or further development of knowledge regarding the structure of matter, there appeared fake concepts of quarks, myons, pions, bosons, etc., that do not exist in the real material world Experimental evidence as to the lack of indivisible quanta in nature [1] seemed to have fixed the intolerable situation but quantum physicists did not “notice” that.
Introduction It is believed that the basic physical building blocks forming the world we live in may be categorized into particles of matter and carriers of force between matter. All known elementary constituents of matter and transmitters of force are quantized. For example, energy, momentum, and angular momentum take on discrete quantized values. The electron is an example of an elementary particle of matter, and the photon is an example of a transmitter of force. Neutrons, protons, and atoms are composite particles made up of elementary particles of matter and transmitters of force. These composite particles are also quantized. Because classical mechanics is unable to explain quantization, we must learn quantum mechanics in order to understand the microscopic properties of atoms – which, for example, make up solids such as crystalline semiconductors. Historically, the laws of quantum mechanics have been established by experiment. The most important early experiments involved light. Long before it was realized that light waves are quantized into particles called photons, key experiments on the wave properties of light were performed. For example, it was established that the color of visible light is associated with different wavelengths of light. Table 2.1 shows the range of wavelengths corresponding to different colors. The connection between optical and electrical phenomena was established by Maxwell in 1864. This extended the concept of light to include the complete electromagnetic spectrum. A great deal of effort was, and continues to be, spent gathering information on the behavior of light.
Quantum mechanics is considered to be one of the most successful as well as revolutionary theories in the history of physics. It gives the conceptual and mathematical basis of the behavior of matter and energy at atomic and subatomic level. In the course of time quantum mechanics has grown out of a theory that was created to cover experimental anomalies to a comprehensive theory that forms the basis of theoretical physics as known today. Its use is much broader to the early atomic models and now it is central to quantum field theory, particle physics and condensed matter physics, cosmology, and new theories of quantum gravity. Quantum mechanics has a significant impact on the philosophical concept of physical reality because of its abstract nature, the probabilistic nature of its interpretations, wave functions and non-local correlations. The classical physics, in contrast to quantum mechanics, presupposes the determinism and exact predictability of the phenomena; quantum mechanics regards the unpredictability of phenomena as the natural law. This change of thought has enabled physicists to develop a set of theoretical frameworks, which better capture experimental data, especially at gross extremes of energy and space. Quantum mechanics is a theory and a method of modern theoretical physics. It allows the development of field theories of the description of fundamental interactions, predicts the occurrence of previously unknown particles, and the explanation of complex collective phenomena in many-body systems. Moreover, additional quantum concepts have already become essential in the study of the early universe, black holes and microphysical geometry of space-time. The purpose of the research paper is to examine the vast number of theoretical physics studies using quantum mechanics as a tool. The paper has emphasised the contribution of quantum mechanics in the current research on the study of unification of physical theories as it is manifested in key subfields to which quantum mechanics has made contributions. There are also some reflections of where quantum mechanics is likely to make a paradigm shift in the future that confirm its relevance as a fundamental pillar of theoretical physics.
This chapter examines the historical development of quantum mechanics, focusing on key experiments and theories that challenged classical physics. It begins with blackbody radiation, highlighting the discrepancy between classical predictions and experimental observations, leading to Planck's quantization hypothesis, which posits that energy is emitted in discrete packets (quanta). The chapter covers the photoelectric effect and Compton scattering, demonstrating wave–particle duality and validating quantum theory. It also discusses atomic models, culminating in the Bohr model and the energy-level diagram of the hydrogen atom, which explains atomic phenomena such as line spectra and discrete energy transitions. The chapter concludes by introducing the quantum model, which supersedes the Bohr model by incorporating wave–particle duality and the uncertainty principle, highlighting the necessity of quantum mechanics for accurate atomic-scale descriptions.