From time immemorial, mankind has manipulated specific properties of materials for specific self-benefits. A clear understanding of the basic principles of materials science is essential for technological development. The rapid development of materials science resulted in the invention of miniature electronic devices. All modern technologically advanced devices are directly related to an understanding of materials at the atomic and sub-atomic levels. Accordingly, the technical universities throughout the world include materials science as an essential ingredient in their course curricula.

Materials science is an interdisciplinary subject relying heavily on basic principles of physics and chemistry. Electrical and thermal conductivity, dielectric constant, magnetization, optical reflection and refraction, strength and toughness etc. are properties that originate from the internal structures of the materials. The present book, entitled Principle of Engineering Physics 2, contains chapters mostly related to materials science. It is designed as a textbook, keeping in view the engineering physics and materials science course curricula prescribed by most technical universities of India. It begins with ‘Crystal Structure’ and ends with ‘Nano Structure & Thin Films’, containing altogether thirteen chapters. The book is written in a logical and coherent manner for easy understanding by students. It presumes a working knowledge of quantum mechanics, optics, electricity and magnetism. Emphasis has been given to an understanding of the basic concepts and their applications to a number of engineering problems. Each topic is discussed in detail both conceptually and mathematically, so that students will not face comprehension difficulties. Derivations and solutions of numerical examples are also provided in detail. Each chapter contains a large number of solved numerical examples, unsolved numerical problems with answers, practical applications, theoretical questions, and multiple choice questions with answers. Certain topics and derivations which are not present in university syllabi have been included in the book for the sake of continuity and completeness. The scope of the book has thus been expanded beyond the basic needs of undergraduate engineering students. We hope, this book will be helpful not only to the students but also to the teachers.

In spite of utmost care, some typographical errors might have inadvertently crept into the book. Readers would be highly appreciated if they convey these errors to the authors. The authors sincerely request the readers for their constructive criticisms via emails mdnkhan1964@yahoo.com and spanigrahi@nitrkl.ac.in for future modification of the book.

Introduction

It is correctly told that mathematics is the queen of all sciences; in the same spirit, quantum physics or quantum mechanics may be called the king of all sciences. Our knowledge in any field of science is incomplete as long as we remain unacquainted with quantum physics. The concepts of quantum physics form the basis for our present understanding of physical phenomena on an atomic and microscopic scale. The concepts of quantum physics can be applied to most fields of science and engineering starting from biology to quantum computers to cosmology. Within engineering, important subjects of practical significance include semiconductor transistors, lasers, quantum optics, and molecular devices where quantum physics plays the most vital role. As technology advances, quantum concepts give birth to an increasing number of new electronic and opto-electronic devices. Their fabrications and functions can only be understood by using quantum physics. Within the next few years, fundamentally quantum devices such as single-electron memory cells and photonic signal processing systems may be available commercially. As nano-and atomicscale devices become easier to manufacture, these sophisticated manufacturing units will require an increasing number of individuals with sound knowledge of quantum physics. Therefore, all universities in the world have included quantum physics as a subject in their technical course curricula. Quantum physics is no longer a theoretical subject with mathematical complexities but an engineering subject!

Need for Quantum Physics

Two time-tested proverbs are, ‘Failure is the pillar of success’ and ‘Necessity is the mother of invention’. Classical physics based on Newtonian laws, thermodynamical laws and classical laws of electromagnetism explained successfully the macroscopic world. The macroscopic world is directly observable or can be made observable by relatively simple devices. However, classical physics failed seriously in explaining the phenomena in the realm of atoms, nucleons and elementary particles. These failures gave birth to a new branch in physics called quantum physics. In the following, we mention a few examples of the failures of classical concepts, though the list is endless.

An accelerated charge emits energy and the electron revolving around a nucleus should emit energy [its energy then should go to zero] resulting in the collapse of the atom; but atom is a stable entity! According to classical theory, the excited hydrogen atom should emit electromagnetic radiations of all the wavelengths continuously.