Physics for Computer Science Students: With Emphasis on Atomic and Semiconductor Physics

535 Pages·1991·41.38 MB·English

by  Narciso Garcia

Physics for Computer
Science Students
Narciso Garcia
Arthur Damask
Physics for Computer
Science Students
With Emphasis on Atomic and
Semiconductor Physics
Springer-Verlag
New York Berlin Heidelberg London Paris
Tokyo Hong Kong Barcelona Budapest
Narciso Garcia
Arthur Damask
Physics Department
Queen's College
of the City University of New York
Flushing, NY 11367
USA
Library of Congress Cataloging in Publication Data
Garcia, Narciso
Physics for computer science students.
Includes index.
1. Physics 2. Computers. I. Damask, A. C. ll. Title.
QC21.2.G32 530 91-31527
Printed on acid-free paper.
© 1991 Springer-Verlag New York Inc.
All rights reserved. This work may not be translated or copied in whole or in part without the written per
mission of the publisher (Springer-Verlag New York, Inc., 175 Fifth Avenue, New York, NY 10010, USA),
except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of
information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar
methodology now known or hereafter developed is forbidden.
The use of general descriptive names, trade names, trademarks, etc., in this publication, even if the former are
not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and
Merchandise Marks Act, may accordingly be used freely by anyone.
987 6 543 2 1
ISBN-13: 978-0-387-97656-3 e-ISBN-13: 978-1-4684-0421-0
001: 10.10071978-1-4684-0421-0
Preface
This text is the product of several years' effort to develop a course to fill a
specific educational gap. It is our belief that computer science students should
know how a computer works, particularly in light of rapidly changing tech
nologies. The text was designed for computer science students who have a
calculus background but have not necessarily taken prior physics courses.
However, it is clearly not limited to these students. Anyone who has had
first-year physics can start with Chapter 17. This includes all science and
engineering students who would like a survey course of the ideas, theories,
and experiments that made our modern electronics age possible.
This textbook is meant to be used in a two-semester sequence. Chapters
1 through 16 can be covered during the first semester, and Chapters 17 through
28 in the second semester. At Queens College, where preliminary drafts have
been used, the material is presented in three lecture periods (50 minutes each)
and one recitation period per week, 15 weeks per semester. The lecture and
recitation are complemented by a two-hour laboratory period per week for
the first semester and a two-hour laboratory period biweekly for the second
semester.
Computer Science students are usually required to take one year of phys
ics; therefore, we examined conventional first-year physics courses with care
so as to delete topics not relevant to the physics of semiconductors and logic
circuits (such as Bernoulli's equation or nuclear decay rates). To achieve this
contraction with some precision, we developed the second semester, Chapters
17-28, and taught these chapters for two years before writing Chapters 1-16
for the first semester.
The first-semester chapters include the First Principles of physics. The
student normally develops the concepts of sliding and colliding blocks because
these can be readily visualized and the principles understood from common
experience. These concepts are later applied to electrons and holes, which
are not readily visualized; hence the early foundation permits the understand
ing of more complex conceptual models.
The second part of this textbook begins with a presentation of some of
the phenomena that led to the breakdown of classical physics and the advent
of the quantum in blackbody radiation, photoelectric effect, electromagnetic
spectrum of atoms, and so forth (Chapters 17 and 18). After laying down the
fundamental principles of wave mechanics, de Broglie's hypothesis, and the
Uncertainty Principle, we introduce the student to the Schrodinger theory of
quantum physics. This theory is applied to the simple example of the infinite
potential well (Chapters 19 and 20). An outline of the solution of the Schro
dinger equation (i.e., the three quantum numbers n, i, ml) and some of the
features of the wavefunctions are presented in Chapter 21. After investigating
vi PREFACE
the need for the electron spin, we use these results, together with Pauli's
exclusion principle, to determine the electron configurations and some of the
properties of multi-electron atoms.
The student is then ready to study the electrical properties of solids. A
brief discussion of the crystal structure and bonding mechanisms (Chapter
22) precedes the presentation of the classical and quantum free electron the
ories and their successes and shortcomings (Chapter 23). In order to explain
the large differences in the electrical properties of solids as well as the peculiar
properties of semiconductors, the existence of allowed and forbidden energy
bands is investigated (Chapter 24). In this chapter, we introduce the concepts
of the electron effective mass and of holes. Intrinsic and doped semiconduc
tors, their electron and hole densities, and their electrical properties are dis
cussed in Chapter 25.
It is now a rather simple matter for the student to understand the behavior
and the characteristics of semiconductor devices: diodes, bipolar transistors,
field effect transistors, etc. Semiconductor devices are the subject of Chapter
26. The text concludes with two chapters unique to this physics textbook. In
Chapter 27, we show how diodes and transistors can be used to construct
the logic circuits (gates) that constitute the fundamental building blocks of
the computer. Chapter 28 is a layman's introduction to some of the techniques
used in the fabrication of integrated circuits.
The laboratory experiments for the first semester are standard in any
physics department, and thus we do not feel that is is necessary to include
them in this book. The seven experiments in the second semester have been
designed to illustrate important measurements; they are not standard in most
physics courses. The equipment needed for these experiments is not generally
available in quantity in physics departments but can be ordered from standard
suppliers or constructed in school shops. For this reason the seven laboratory
experiments are described in the instructor's manual that complements this
textbook.
Although some of the topics and the level of treatment of Chapters 20-
27 may appear to be potentially formidable for a first course in physics, in
practice they have proved not to be so. We have tried to soften the impact
of mathematical complexities with intuitive physical arguments. For example,
the existence of energy bands in solids is first introduced by outlining the
solution of the Schr6dinger equation for an electron moving in the periodic
potential of the ions. The student is shown that the imposition of the boundary
conditions leads to a transcendental equation for the dispersion relation whose
numerical solution leads in turn to the existence of forbidden and allowed
energy bands. (Students are encouraged to use their computer programming
skills to solve this equation.) This presentation is followed by an alternative
approach that relies on simple intuitive arguments; here, the mathematics is
kept to a minimum. The student is shown how, when two atoms are brought
together to form a molecule, two separate energy levels are formed from each
level of the individual atom. This is then extended to a situation where a large
number of atoms come together to form a solid. It is thus relatively simple
PREFACE vii
to show that each atomic level becomes a band of very closely spaced energy
levels.
By blending mathematical and physical arguments, we believe we have
achieved a thorough presentation of the concepts of solid state physics while
staying within the reach of students with an intermediate background in
mathematics.
Narciso Garcia
Arthur C. Damask
Acknowledgments
The course for which this text was developed was conceived by Professor Joseph
Klarfeld of the Physics Department and Professor Jacob Rootenberg, Chairman of the
Computer Science Department of Queens College. Many useful suggestions on style,
pace, and content were made by Professor Arthur Paskin of the Physics Department,
who taught the course for several trial semesters. Topics requiring fuller explanation
and wording requiring greater clarity were pointed out by Jay Damask, a high school
junior with a knowledge of elementary calculus.
We appreciate the thorough work and many suggestions of the reviewers of this
. book: Professor Joseph I. Budnick-University of Connecticut, CT, Professor William
Faissler-Northeastern University, MA, Professor David B. Fenner-University of Santa
Clara, CA, Professor H. L. Helfer-The University of Rochester, NY, Professor Marvin
D. Kemple-Purdue University, IN, and Professor Lawrence A. Mink-Arkansas State
University, AR. The manuscript was typed and prepared for the publisher by Mrs.
Marion Gaffga of Spring Hill, Florida. Mrs. Shirley Allen and Mrs. Susan Wasserman
of Queens College contributed to the typing.
N.G.
A. C. D.
Contents
CHAPTER 1 Physical Quantities 1
1.1 Introduction 2
1.2 Quantities and Units 3
1.3 Powers of 10 5
1.4 Accuracy of Numbers 6
CHAPTER 2 Vectors 9
2.1 Introduction 10
2.2 Vector Components 10
2.3 Unit Vectors 14
2.4 Dot Product 15
2.5 Cross Product 16
CHAPTER 3 Uniformly Accelerated Motion 21
3.1 Introduction 22
3.2 Speed and Velocity 22
3.3 Acceleration 24
3.4 Linear Motion 25
3.5 Projectile Motion 30
CHAPTER 4 Newton's Laws 37
4.1 Introduction 38
4.2 Newton's Laws 38
4.3 Mass 41
4.4 Weight 42
4.5 Applications of Newton's Laws 43
4.6 Friction 48
CHAPTER 5 Work, Energy and Power 53
5.1 Introduction 54
5.2 Work 54
5.3 Potential Energy 56
5.4 Work Done by a Variable Force 57
5.5 Kinetic Energy 58
5.6 Energy Conservation 59
5.7 Power 62
xii CONTENTS
CHAPTER 6 Momentum and Collisions 67
6.1 Introduction 68
6.2 Center of Mass 68
6.3 Motion of the Center of Mass 71
6.4 Momentum and its Conservation 72
6.5 Collisions 74
CHAPTER 7 Rotational Motion 81
7.1 Introduction 82
7.2 Measurement of Rotation 82
7.3 Rotational Motion 83
7.4 Equations of Rotational Motion 86
7.5 Radial Acceleration 88
7.6 Centripetal Force 89
7.7 Orbital Motion and Gravitation 91
CHAPTER 8 Rotational Dynamics 97
8.1 Introduction 98
8.2 Moment of Inertia and Torque 98
8.3 Rotational Kinetic Energy 101
8.4 Power 105
8.5 Angular Momentum 106
8.6 Conservation of Angular Momentum 107
CHAPTER 9 Kinetic Theory of Gases and the Concept
of Temperature 111
9.1 Introduction 112
9.2 Molecular Weight 112
9.3 Thermometers 113
9.4 Ideal Gas Law and Absolute Temperature 114
9.5 Kinetic Theory of Gas Pressure 117
9.6 Kinetic Theory of Temperature 119
9.7 Measurement of Heat . 121
9.8 Specific Heats of Gases 122
9.9 Work Done by a Gas 123
9.10 First Law of Thermodynamics 124
Supplement 9.1 Maxwell-Boltzmann Statistical Distribution 126
CHAPTER 10 Oscillatory Motion 131
10.1 Introduction 132
10.2 Characterization of Springs 132
10.3 Frequency and Period 133
10.4 Amplitude and Phase Angle 134
10.5 Oscillation of a Spring 134
10.6 Energy of Oscillation 140
CONTENTS xiii
CHAPTER 11 Wave Motion 145
11.1 Introduction 146
11.2 Wavelength, Velocity, Frequency, and Amplitude 146
11.3 Traveling Waves in a String 147
11.4 Energy Transfer of a Wave 151
CHAPTER 12 Interference of Waves 157
12.1 Introduction 158
12.2 The Superposition Principle 158
12.3 Interference from Two Sources 159
12.4 Double Slit Interference of Light 162
12.5 Single Slit Diffraction 166
12.6 Resolving Power 168
12.7 X-Ray Diffraction by Crystals: Bragg Scattering 170
12.8 Standing Waves 173
CHAPTER 13 Electrostatics 177
13.1 Introduction 178
13.2 Attraction and Repulsion of Charges 178
13.3 Coulomb's Law 179
13.4 Charge of an Electron 182
13.5 Superposition Principle 183
CHAPTER 14 The Electric Field and the
Electric Potential 187
14.1 Introduction 188
14.2 The Electric Field 188
14.3 Electrical Potential Energy 191
14.4 Electric Potential 194
14.5 The Electron Volt 197
14.6 Electromotive Force 197
14.7 Capacitance 198
CHAPTER 15 Electric Current 2Q3
15.1 Introduction 204
15.2 Motion of _Charges in an Electric Field 204
15.3 Electric Current 205
15.4 Resistance and Resistivity 208
15.5 Resjstances in Series and Parallel 210
15.6 Kirchhoff's Rules 214
15.7 Ammeters and Voltmeters 219
15.8 Power Dissipation by Resistors 221
15.9 Charging a Capacitor-RC Circuits 222