Third Edition
ENGINEERING
PHYSICS
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K. Rajagopal
ENGINEERING PHYSICS
ENGINEERING PHYSICS
THIRD EDITION
K. Rajagopal
Professor of Physics
Government College of Engineering
Tirunelveli
Delhi-110092
2015
ENGINEERING PHYSICS, Third Edition
K. Rajagopal
© 2015 by PHI Learning Private Limited, Delhi. All rights reserved. No part of this book may
be reproduced in any form, by mimeograph or any other means, without permission in writing
from the publisher.
ISBN-978-81-203-5136-3
The export rights of this book are vested solely with the publisher.
Fifth Printing (Third Edition)
…
…
August, 2015
Published by Asoke K. Ghosh, PHI Learning Private Limited, Rimjhim House, 111,
Patparganj Industrial Estate, Delhi-110092 and Printed by Rajkamal Electric Press, B-35/9,
G.T. Karnal Road Industrial Area, Delhi-110033.
CONTENTS
Preface
xvii
Preface to the First Edition
1.
xix
ELASTICITY ............................................................................................... 1–45
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
1.10
Introduction
1
Stress
1
1.2.1 Tensile Stress
2
1.2.2 Compressional Stress
2
1.2.3 Normal Stress
2
1.2.4 Tangential or Shearing Stress
2
Strain
2
1.3.1 Longitudinal or Linear Strain
2
1.3.2 Bulk or Volumetric Strain
2
1.3.3 Shear Strain
3
Hooke’s Law
3
1.4.1 Stress–Strain Diagram
4
1.4.2 Some Peculiar Phenomena Associated with Elastic Behaviour of Solids
Working Stress and Factors of Safety
6
Factors Affecting Elasticity
6
1.6.1 Effect of Hammering, Rolling and Annealing
6
1.6.2 Effect of Impurities
6
1.6.3 Effect of Change of Temperature
7
Various Kinds of Moduli of Elasticity
7
1.7.1 Young’s Modulus (E or y)
7
1.7.2 Bulk Modulus (k)
8
1.7.3 Rigidity Modulus
9
Relationship between Three Modulii of Elasticity
9
Poisson’s Ratio (g)
11
Torsion on Cylindrical Bodies such as Wires or Rods
17
1.10.1 Introduction
17
1.10.2 Expression for the Couple per Unit Twist of the Wire
17
1.10.3 Efficacy of a Hollow Shaft
19
1.10.4 Shafts and their Applications
19
v
5
vi
Contents
1.10.5
1.10.6
1.10.7
Beams
1.11.1
1.11.2
1.11.3
1.11.4
1.11.5
1.11.6
1.11.7
1.11.8
Torsional Pendulum
20
Torsional Oscillations
20
Determination of Rigidity Modulus of the Wire Using Torsional Pendulum
21
1.11
26
Introduction
26
Bending Moment of a Beam Fixed at One End but Loaded at the Other End
27
Expression for Bending Moment
28
Cantilevers
29
Depression of the Free End of a Cantilever
30
Depression of the Free End of the Cantilever (Alternative Method)
32
Applications of Cantilevers
34
A Beam Supported on Two Knife Edges and Loaded in the Middle
(Non-uniform Bending)
34
1.11.9 Uniform Bending—Elevation of the Mid Point of the Beam Supported
Symmetrically on Two Knife Edges and Equally Loaded at the Ends
35
1.11.10 Experimental Methods of Determination of Young’s Modulus
37
1.11.11 Application of Beams (Shape ‘I’ beam)
40
1.12 Summary
42
Short Answer Questions
43
Long Answer Questions
44
Numerical Problems
44
2.
ACOUSTICS OF BUILDINGS ................................................................... 46–71
2.1
2.2
2.3
Introduction
46
Characteristics of Musical Sound
46
Unit of Loudness
49
2.3.1 Measurement of Loudness
49
2.4
Acoustics of Buildings: Architectural Features
2.5
Acoustical Demands of an Auditorium
57
2.5.1 Proper Reverberation
57
2.5.2 Echoes
59
2.5.3 Design of the Hall
59
2.5.4 Shape of Walls and Ceiling
60
2.5.5 Echelon Effect
60
2.5.6 Extraneous Noises
60
2.6
Sabine’s Reverberation Formula
60
2.7
Absorption Coefficient
65
2.8
Determination of Absorption Coefficient
66
2.9
Summary
68
Short Answer Questions
69
Long Answer Questions
70
Numerical Problems
70
3.
56
ULTRASONICS ...................................................................................... 72–102
3.1
3.2
Introduction
72
Generation of Ultrasonics
73
Contents
Piezoelectric Effect
73
Quartz Crystal
74
Piezoelectric Generator
77
3.5.1 Advantages of Piezoelectric Generator
79
3.6
Magnetostriction Effect
80
3.7
Magnetostriction Oscillator
81
3.7.1 Advantages and Disadvantages of Magnetostriction Oscillator
81
3.8
Detection of Ultrasonics
82
3.9
Properties of Ultrasonics
83
3.10 Determination of Wavelength and Velocity of Ultrasonic Waves in Liquids
3.11 Industrial Applications of Ultrasonics in Engineering
85
3.11.1 Ultrasonic Cleaning
85
3.11.2 Ultrasonic Drilling
86
3.11.3 Ultrasonic Welding
87
3.11.4 Ultrasonic Soldering
88
3.12 Sonar (sound navigation and ranging)
89
3.13 Ultrasonic Flaw Detection
90
3.13.1 Introduction
90
3.13.2 Principle of Operation
90
3.13.3 Testing Devices
90
3.13.4 Testing Methods
93
3.13.5 Visual Display Units
93
3.13.6 Advantages of Ultrasonic NDT
95
3.13.7 Limitations of Ultrasonic NDT
95
3.13.8 Applications of Ultrasonic NDT
95
3.14 Medical Applications of Ultrasonics
95
3.14.1 Introduction
95
3.14.2 Sonography
95
3.14.3 Ultrasonic Imaging Techniques
96
3.14.4 Different Modes of Scanning
97
3.14.5 Doppler Sonography
97
3.14.6 Therapeutic Applications of Ultrasound
98
3.14.7 Advantages of Ultrasonics
98
3.14.8 Limitations of Ultrasonics
99
3.14.9 Risks and Side Effects
99
3.15 Other Applications of Ultrasonics
99
3.16 Summary
100
Short Answer Questions
101
Long Answer Questions
102
Numerical Problems
102
vii
3.3
3.4
3.5
4.
84
CRYSTAL PHYSICS ............................................................................. 103–144
4.1
4.2
4.3
4.4
Introduction
103
Space Lattice
104
Translation Vectors
104
The Basis and Crystal Structure
105
viii
Contents
4.5
4.6
4.7
4.8
Unit Cell and Lattice Parameters
105
Bravais Lattices
108
The Cubic Crystal
110
Important Parameters of Cubic Lattices
110
4.8.1 Number of Atoms Per Unit Cell
110
4.8.2 Coordination Number
111
4.8.3 Atomic Radius
111
4.8.4 Packing Density or Packing Factor
113
4.9
Calculation of Lattice Constant
114
4.10 Some Crystal Structures
115
4.10.1 Structure of Diamond
115
4.10.2 Zinc Blende
118
4.10.3 Caesium Chloride
118
4.10.4 Barium Titanate
119
4.10.5 Sodium Chloride
119
4.11 Effect of Temperature and Pressure on Crystal Structures
119
4.12 Close-packed Structures
120
4.13 Hexagonally Close-packed Structure (HCP)
122
4.14 Directions and Miller Indices
125
4.15 Rules for Finding Miller Indices
126
4.16 Important Features of Miller Indices
126
4.17 Miller Indices for a Cubic Crystal
127
4.18 Relation between Interplanar Spacing d and Cube Edge a
127
4.19 Allotropy and Polymorphism
131
4.19.1 Crystal Growth Techniques
132
4.19.2 Solution Growth Method
132
4.19.3 Melt-growth Process
133
4.19.4 Floating Zone Method (Bridgeman Method)
134
4.19.5 Production of Single Crystal by Czocharalski Method
134
4.19.6 Vapour Deposition Technique
135
4.20 Crystal Imperfections
136
4.20.1 Point Defects
136
4.20.2 Effect of Point Defects
138
4.20.3 Line Defects
138
4.20.4 Properties of Dislocations
140
4.20.5 Surface Defects
140
4.21 Summary
142
Short Answer Questions
143
Long Answer Questions
143
Numerical Problems
144
5.
WAVE OPTICS ..................................................................................... 145–173
5.1
5.2
5.3
Introduction
145
Michelson’s Interferometer
5.2.1 Applications
147
Polarization
149
5.3.1 Plane Polarized Light
145
150
Contents
ix
5.3.2 Polarization by Reflection
151
5.3.3 Plane Polarized Light Using Piles of Plates
152
5.3.4 Double Refraction
152
5.3.5 Elliptically and Circularly Polarized Light
153
5.3.6 Retarding Plates
155
5.3.7 Production of Plane, Circular and Elliptically Polarized Light
156
5.3.8 Detection of Plane, Circular, and Elliptically Polarized Light
158
5.3.9 Analysis of the Given Beam of Light
159
5.4
Photoelasticity
161
5.4.1 Stress Optic Law
162
5.4.2 Relation between Principal Stresses and Angular Phase Difference
162
5.4.3 Plane Polariscope
164
5.4.4 Circular Polariscope (Photoelastic Bench)
167
5.4.5 Applications of Photoelasticity
168
5.5
Summary
168
Short Answer Questions
171
Long Answer Questions
172
Numerical Problems
172
6.
LASERS ................................................................................................ 174–204
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
6.11
6.12
Introduction
174
Properties of Lasers
174
Stimulated Absorption, Spontaneous Emission and Stimulated Emission
6.3.1 Stimulated Absorption
177
6.3.2 Spontaneous and Stimulated Emission
178
Relation between Einstein’s A and B Coefficients
179
Population Inversion
180
Pumping
181
Main Components of a Laser
182
Nd:Yag Laser
183
Helium–Neon Laser
184
6.9.1 Apparatus Construction
185
6.9.2 Operations
185
6.9.3 Important Features
187
6.9.4 Advantages
187
6.9.5 Uses
187
CO2 Laser
187
Semiconductor Lasers
190
6.11.1 Homojunction Laser
190
6.11.2 Heterojunction Semiconductor Laser
192
Applications of Laser in Material Processing
194
6.12.1 Laser Cutting
194
6.12.2 Laser Welding
195
6.12.3 Hole Drilling
196
6.12.4 Other Applications
196
6.12.5 CD-ROM (Compact Disk Read Only Memory)
196
177
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