ENGINEERING PHYSICS Dr S. Mani Naidu M.Sc., Ph.D., P.G.D.C.A. Associate Professor of Physics Sree Vidyanikethan Engineering College Tirupati, Andhra Pradesh Copyright © 2013 Dorling Kindersley (India) Pvt. Ltd. Licensees of Pearson Education in South Asia No part of this eBook may be used or reproduced in any manner whatsoever without the publisher’s prior written consent. This eBook may or may not include all assets that were part of the print version. The publisher reserves the right to remove any material in this eBook at any time. ISBN 9788131761632(cid:13)(cid:10) eISBN 9789332514126(cid:13)(cid:10) Head Office: A-8(A), Sector 62, Knowledge Boulevard, 7th Floor, NOIDA 201 309, India Registered Office: 11 Local Shopping Centre, Panchsheel Park, New Delhi 110 017, India Brief Contents Preface xv Chapter 1 Bonding in Solids 1-1 Chapter 2 Crystal Structures 2-1 Chapter 3 Crystal Planes, X-ray Diffraction and Defects in Solids 3-1 Chapter 4 Elements of Statistical Mechanics and Principles of Quantum Mechanics 4-1 Chapter 5 Electron Theory of Metals 5-1 Chapter 6 Dielectric Properties 6-1 Chapter 7 Magnetic Properties 7-1 Chapter 8 Semiconductors and Physics of Semiconductor Devices 8-1 Chapter 9 Superconductivity 9-1 Chapter 10 Lasers 10-1 Chapter 11 Fibre Optics 11-1 Chapter 12 Holography 12-1 Chapter 13 Acoustics of Buildings and Acoustic Quieting 13-1 iv Brief Contents Chapter 14 Nanotechnology 14-1 Chapter 15 Optics 15-1 Chapter 16 Non-destructive Testing Using Ultrasonics 16-1 Chapter 17 Nuclear Physics 17-1 Chapter 18 Electromagnetic Waves 18-1 Chapter 19 Special theory of Relativity: Relativistic Mechanics 19-1 Index I-1 Contents  Preface xv Chapter 1 Bonding in Solids 1-1 1.1 Different types of bonding in solids 1-1 1.2 Cohesive energy and estimation of cohesive energy of ionic solids 1-4 1.3. Estimation of cohesive energy of NaCl molecule in a solid 1-8 1.4 Madelung constant 1-9 Formulae 1-10 Solved Problems 1-11 Multiple-choice Questions 1-14 Answers 1-16 Review Questions 1-16 Chapter 2 Crystal Structures 2-1 2.1 Introduction 2-1 2.2 Space lattice (or) crystal lattice 2-2 2.3 The basis and crystal structure 2-3 2.4 Unit cell and lattice parameters 2-3 2.5 Crystal systems and Bravais lattices 2-4 2.6 Structure and packing fractions of simple cubic [SC] structure 2-9 2.7 Structure and packing fractions of body-centred cubic structure [BCC] 2-10 2.8 Structure and packing fractions of face-centred cubic [FCC] structure 2-11 2.9 Diamond cubic structure 2-12 2.10 NaCl crystal structure 2-13 vi Contents 2.11 Caesium chloride [CsCl] structure 2-14 2.12 Zinc sulphide [ZnS] structure 2-14 2.13 Stacking sequence in metallic crystals 2-15 2.14 Calculation of lattice constant 2-16 Solved Problems 2-17 Multiple-choice Questions 2-19 Answers 2-22 Review Questions 2-22 Chapter 3 C rystal Planes, X-ray Diffraction and Defects in Solids 3-1 3.1 Crystal planes, directions and Miller indices 3-1 3.2 Distance of separation between successive hkl planes 3-4 3.3 Imperfections in crystals 3-7 3.4 Energy for the formation of a vacancy and number of vacancies — at equilibrium concentration 3-11 3.5 Diffraction of X-rays by crystal planes and Bragg’s law 3-15 3.6 Powder method 3-17 3.7 Laue method 3-18 Formulae 3-19 Solved Problems 3-20 Multiple-choice Questions 3-27 Answers 3-32 Review Questions 3-32 Chapter 4 E lements of Statistical Mechanics and Principles of Quantum Mechanics 4-1 4.1 Introduction 4-1 4.2 Phase space 4-1 4.3 Maxwell–Boltzmann distribution 4-1 4.4 Fermi–Dirac distribution 4-3 4.5 Bose–Einstein distribution 4-5 4.6 Comparison of Maxwell–Boltzmann, Fermi–Dirac and Bose–Einstein distributions 4-7 4.7 Photon gas 4-7 4.8 Concept of electron gas and Fermi energy 4-8 4.9 Density of electron states 4-8 4.10 Black body radiation 4-11 4.11 Waves and particles—de Broglie hypothesis—Matter waves 4-12 Contents vii 4.12 Relativistic correction 4-15 4.13 Planck’s quantum theory of black body radiation 4-18 4.14 Experimental study of matter waves 4-19 4.14 Schrödinger’s time-independent wave equation 4-26 4.15 Heisenberg uncertainty principle 4-29 4.16 Physical significance of the wave function 4-31 4.17 Particle in a potential box 4-32 Formulae 4-41 Solved Problems 4-42 Multiple-choice Questions 4-48 Answers 4-53 Review Questions 4-53 Chapter 5 Electron Theory of Metals 5-1 5.1 Introduction 5-1 5.2 Classical free electron theory of metals 5-2 5.3 Relaxation time, mean free path, mean collision time and drift velocity 5-5 5.4 Fermi-Dirac distribution 5-7 5.5 Quantum free electron theory of electrical conduction 5-9 5.6 Sources of electrical resistance 5-11 5.7 Band theory of solids 5-12 5.8 Bloch theorem 5-20 5.9 Origin of energy bands formation in solids 5-22 5.10 Velocity and effective mass of an electron 5-22 5.11 Distinction between metals, semiconductors and insulators 5-25 Formulae 5-28 Solved Problems 5-28 Multiple-choice Questions 5-36 Answers 5-39 Review Questions 5-40 Chapter 6 Dielectric Properties 6-1 6.1 Introduction 6-1 6.2 Dielectric constant 6-1 6.3 Internal or local field 6-2 6.4 Clausius–Mosotti relation 6-4 6.5 Orientational, ionic and electronic polarizations 6-7 viii Contents 6.6 Frequency dependence of polarizability: (Dielectrics in alternating fields) 6-12 6.7 Piezoelectricity 6-17 6.8 Ferroelectricity 6-18 6.9 Frequency dependence of dielectric constant 6-20 6.10 Important requirements of insulators 6-22 Formulae 6-23 Solved Problems 6-24 Multiple-choice Questions 6-29 Answers 6-34 Review Questions 6-34 Chapter 7 Magnetic Properties 7-1 7.1 Magnetic permeability 7-1 7.2 Magnetization (M ) 7-2 7.3 Origin of magnetic moment—Bohr magneton—electron spin 7-2 7.4 Classification of magnetic materials 7-5 7.5 Classical theory of diamagnetism [Langevin theory] 7-7 7.6 Theory of paramagnetism 7-9 7.7 Domain theory of ferromagnetism 7-12 7.8 Hysteresis curve 7-17 7.9 Anti-ferromagnetic substances 7-18 7.10 Ferrimagnetic substances [Ferrites] 7-20 7.11 Soft and hard magnetic materials 7-20 7.12 Applications of ferrites 7-22 Formulae 7-23 Solved Problems 7-23 Multiple-choice Questions 7-26 Answers 7-30 Review Questions 7-31 Chapter 8 S emiconductors and Physics of Semiconductor Devices 8-1 8.1 Introduction 8-1 8.2 Intrinsic semiconductors—carrier concentration 8-1 8.3 Electrical conductivity of a semiconductor 8-11 8.4 Extrinsic semiconductors 8-15 8.5 Carrier concentration in extrinsic semiconductors 8-18 Contents ix 8.6 Minority carrier life time 8-21 8.7 Drift and diffusion currents 8-23 8.8 Einstein’s relations 8-26 8.9 Continuity equation 8-27 8.10 Hall effect 8-31 8.11 Direct and indirect band gap semiconductors 8-33 8.12 Formation of p-n junction 8-35 8.13 Energy band diagram of p-n diode 8-38 8.14 Diode equation 8-39 8.15 p-n junction biasing 8-40 8.16 V–I characteristics of p-n diode 8-42 8.17 p-n diode rectifier 8-44 8.18 Light emitting diode [LED] 8-49 8.19 Liquid crystal display (LCD) 8-52 8.20 Photodiodes 8-54 Formulae 8-57 Solved Problems 8-59 Multiple-choice Questions 8-66 Answers 8-72 Review Questions 8-73 Chapter 9 Superconductivity 9-1 9.1 Introduction 9-1 9.2 General features of superconductors 9-3 9.3 Type-I and Type-II superconductors 9-8 9.4 Penetration depth 9-9 9.5 Flux quantization 9-11 9.6 Quantum tunnelling 9-12 9.7 Josephson’s effect 9-14 9.8 BCS theor y 9-16 9.9 Applications of superconductivity 9-19 Formulae 9-23 Solved Problems 9-23 Multiple-choice Questions 9-25 Answers 9-29 Review Questions 9-29 Chapter 10 Lasers 10-1 10.1 Introduction 10-1 10.2 Characteristics of laser radiation 10-1