Table Of Content
M O D E R N
P H Y S I C S
M O D E R N
P H Y S I C S
Third edition
K e n n e t h S. K r a n e
DEPARTMENT OF PHYSICS
OREGON STATE UNIVERSITY
JOHNWILEY&SONS,INC
VPANDEXECUTIVEPUBLISHER KayePace
EXECUTIVEEDITOR StuartJohnson
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LibraryofCongressCataloging-in-PublicationData
Krane,KennethS.
Modernphysics/KennethS.Krane.--3rded.
p.cm.
Includesbibliographicalreferencesandindex.
ISBN978-1-118-06114-5(hardback)
1.Physics.I.Title.
QC21.2.K72012
539--dc23
2011039948
PrintedintheUnitedStatesofAmerica
10987654321
PREFACE
This textbook is meant to serve a first course in modern physics, including
relativity,quantummechanics,andtheirapplications.Suchacourseoftenfollows
the standard introductory course in calculus-based classical physics. The course
addresses two different audiences: (1) Physics majors, who will later take a
morerigorouscourseinquantummechanics,findanintroductorymoderncourse
helpful in providing background for the rigors of their imminent coursework
in classical mechanics, thermodynamics, and electromagnetism. (2) Nonmajors,
who may take no additional physics class, find an increasing need for concepts
frommodernphysicsintheirdisciplines—aclassicalintroductorycourseisnot
sufficient background for chemists, computer scientists, nuclear and electrical
engineers,ormolecularbiologists.
Necessaryprerequisitesforundertakingthetextincludeanystandardcalculus-
basedcoursecoveringmechanics,electromagnetism,thermalphysics,andoptics.
Calculusisusedextensively,butnopreviousknowledgeofdifferentialequations,
complex variables, or partial derivatives is assumed (although some familiarity
withthesetopicswouldbehelpful).
Chapters1–8constitutethecoreofthetext.Theycoverspecialrelativityand
quantum theory through atomic structure. At that point the reader may continue
with Chapters 9–11 (molecules, quantum statistics, and solids) or branch to
Chapters 12–14 (nuclei and particles). The final chapter covers cosmology and
canbeconsideredthecapstoneofmodernphysicsasitbringstogethertopicsfrom
relativity(specialandgeneral)aswellasfromnearlyallofthepreviousmaterial
coveredinthetext.
The unifying theme of the text is the empirical basis of modern physics.
Experimentaltestsofderivedpropertiesarediscussedthroughout.Theseinclude
thelatesttestsofspecialandgeneralrelativityaswellasstudiesofwave-particle
duality for photons and material particles. Applications of basic phenomena are
extensivelypresented,anddatafromtheliteratureareusednotonlytoillustrate
those phenomena but to offer insight into how “real” physics is done. Students
usingthetexthavetheopportunitytostudyhowlaboratoryresultsandtheanalysis
based on quantum theory go hand-in-hand to illuminate such diverse topics as
Bose-Einsteincondensation,heatcapacitiesofsolids,paramagnetism,thecosmic
microwave background radiation, X-ray spectra, dilute mixtures of 3He in 4He,
andmolecularspectroscopyoftheinterstellarmedium.
Thisthirdeditionoffersmanychangesfromthepreviousedition.Mostofthe
chapters have undergone considerable or complete rewriting. New topics have
beenintroducedandothershavebeenrearranged.Moreexperimentalresultsare
presentedandrecentdiscoveriesarehighlighted,suchastheWMAPmicrowave
background data and Bose-Einstein condensation. End-of-chapter problem sets
now include problems organized according to chapter section, which offer the
studentanopportunitytogainfamiliaritywithaparticulartopic,aswellasgeneral
problems,whichoftenrequirethestudenttoapplyabroaderarrayofconceptsor
techniques. The number of worked examples in the chapters and the number of
end-of-chapter questions and problems have each increased by about 15% from
thepreviousedition.Therangeofabilitiesrequiredtosolvetheproblemshasbeen
vi Preface
broadened,sothatthiseditionincludesbothmorestraightforwardproblemsthat
buildconfidenceaswellasmoredifficultproblemsthatwillchallengestudents.
Each chapter now includes a brief summary of the important points. Some of
the end-of-chapter problems are available for assignment using the WebAssign
program(www.webassign.net).
Anewdevelopmentinphysicsteachingsincetheappearanceofthe2ndedition
ofthistexthasbeentheavailabilityofalargeandrobustbodyofliteraturefrom
physics education research (PER). My own teaching style has been profoundly
influenced by PER findings, and in preparing this new edition I have tried
to incorporate PER results wherever possible. One of the major themes that
has emerged from PER in the past decade or two is that students can often
learn successful algorithms for solving problems while lacking a fundamental
understanding of the underlying concepts. Many approaches to addressing this
problem are based on pre-class conceptual exercises and in-class individual or
groupactivitiesthathelpstudentstoreasonthroughdiverseproblemsthatcan’tbe
resolvedbypluggingnumbersintoanequation.Itisabsolutelyessentialtodevote
class time to these exercises and to follow through with exam questions that
requiresimilaranalysisandarticulationoftheconceptualreasoning.Moredetails
regarding the application of PER to the teaching of modern physics, including
references to articles from the PER literature, are included in the Instructor’s
Manual for this text, which can be found at www.wiley.com/college/krane. The
Instructor’s Manual also includes examples of conceptual questions for in-class
discussionorexamsthathavebeendevelopedandclasstestedthroughthesupport
of a Course, Curriculum and Laboratory Improvement grant from the National
ScienceFoundation.
Specificchangestothechaptersincludethefollowing:
Chapter1:ThesectionsonUnitsandDimensionsandonSignificantFigures
have been removed. In their place, a more detailed review of applications
of classical energy and momentum conservation is offered. The need for
special relativity is briefly established with a discussion of the failures of
theclassicalconceptsofspaceandtime,andtheneedforquantumtheoryis
previewedinthefailureofMaxwell-Boltzmannparticlestatisticstoaccount
fortheheatcapacitiesofdiatomicgases.
Chapter2:Spacetimediagramshavebeenintroducedtohelpillustraterelation-
ships in the twin paradox. The application of the relativistic conservation
laws to decay and collisions processes is now given a separate section to
help students learn to apply those laws. The section on tests of special
relativityhasbeenupdatedtoincluderecentresults.
Chapter 3: The section on thermal radiation has been rewritten, and more
detailed derivations of the Rayleigh-Jeans and Planck formulas are now
given.
Chapter 4: New experimental results for particle diffraction and interference
arediscussed.Thesectionsontheclassicaluncertaintyrelationshipsandon
wavepacketconstructionandmotionhavebeenrewritten.
Chapter 5: To help students understand the processes involved in applying
boundaryconditionstosolutionsoftheSchro¨dingerequation,anewsection
onwaveboundaryconditionshasbeenadded.Anewintroductorysection
on particle confinement introduces energy quantization and helps to build
theconnectionbetweenthewavefunctionandtheuncertaintyrelationships.
Timedependenceofthewavefunctionisintroducedmoreexplicitlyatan
Preface vii
earlier stage in the formulism. Graphic illustrations for step and barrier
problems now show the real and imaginary parts of the wave function as
wellasitssquaredmagnitude.
Chapter 6: The derivation of the Thomson model scattering angle has been
modified, and the section on deficiencies of the Bohr model has been
rewritten.
Chapter 7: To ease the entry into the 3-dimensional Schro¨dinger analysis of
the hydrogen atom in spherical coordinates, a new section on the one-
dimensionalhydrogenatomhasbeenadded.Angularmomentumconcepts
relatingtothehydrogenatomarenowintroducedbeforethefullsolutions
tothewaveequation.
Chapter8:Muchofthematerialhasbeenreorganizedforclarityandeaseof
presentation.Thescreeningdiscussionhasbeenmademoreexplicit.
Chapter9:Moreemphasishasbeengiventotheuseofbondingandantibonding
orbitalstopredicttherelativestabilityofmolecules.Sectionsonmolecular
vibrationsandrotationshavebeenrewritten.
Chapter 10: This chapter has been extensively rewritten. A new section on
thedensityofstatesfunctionallowsstatisticaldistributionsforphotonsor
particles to be discussed more rigorously. New applications of quantum
statisticsincludeBose-Einsteincondensation,whitedwarfstars,anddilute
mixturesof3Hein4He.
Chapter11:Thechapterhasbeenrewrittentobroadentheapplicationsofthe
quantumtheoryofsolidstoincludenotonlyelectricalconductivitybutalso
theheatcapacityofsolidsandparamagnetism.
Chapter12:Toemphasizetheunityofvarioustopicswithinmodernphysics,
this chapter now includes proton and neutron separation energies, a new
sectiononquantumstatesinnuclei,andnuclearvibrationalandrotational
states,allofwhichhaveanaloguesinatomicormolecularstructure.
Chapter13:Thediscussionofthephysicsoffissionhasbeenexpandedwhile
that of the properties of nuclear reactors has been reduced somewhat.
Becausemuchcurrentresearchinnuclearphysicsisrelatedtoastrophysics,
thischapternowfeaturesasectiononnucleosynthesis.
Chapter 14: New material on quarkonium and neutrino oscillations has been
added.
Chapter 15: Chapters 15 and 16 of the 2nd edition have been collapsed into
a single chapter on cosmology. New results from COBE and WMAP are
included,alongwithdiscussionsofthehorizonandflatnessproblems(and
theirinflationarysolution).
Manyreviewersandclass-testersofthemanuscriptofthiseditionhaveoffered
suggestions to improve both the physics and its presentation. I am particularly
gratefulto:
DavidBannon,OregonStateUniversity
GeraldCrawford,FortLewisCollege
LutherFrommhold,UniversityofTexas-Austin
GaryGoldstein,TuftsUniversity
LeonGunther,TuftsUniversity
GaryIhas,UniversityofFlorida
viii Preface
PaulLee,CaliforniaStateUniversity,Northridge
JeffLoats,MetropolitanStateCollegeofDenver
JayNewman,UnionCollege
StephenPate,NewMexicoStateUniversity
DavidRoundy,OregonStateUniversity
RichSchelp,ErskineCollege
WeidianShen,EasternMichiganUniversity
HongtaoShi,SonomaStateUniversity
JanetTate,OregonStateUniversity
JeffreyL.Wragg,CollegeofCharleston
WeldonWilson,UniversityofCentralOklahoma
I am also grateful for the many anonymous comments from students who used
themanuscriptatthetestsites.Iamindebtedtoallthosereviewersandusersfor
theircontributionstotheproject.
Fundingforthedevelopmentandtestingofthesupplementalexercisesinthe
Instructor’s Manual was provided through a grant from the National Science
Foundation. I am pleased to acknowledge their support. Two graduate students
at Oregon State University helped to test and implement the curricular reforms:
K. C. Walsh and Pornrat Wattasinawich. I appreciate their assistance in this
project.
The staff at John Wiley & Sons have been especially helpful throughout the
project. I am particularly grateful to: Executive Editor Stuart Johnson for his
patienceandsupportinbringingtheneweditionintoreality;AssistantProduction
Editor Elaine Chew for handling a myriad of complicated composition and
illustration details with efficiency and good humor; and Photo Editor Sheena
Goldstein for helping me navigate the treacherous waters of new copyright and
permissionrestrictions.
Inmyresearchandotherprofessionalactivities,Ioccasionallymeetphysicists
whousedearliereditionsofthistextwhentheywerestudents.Somereportthat
theirfirstexposuretomodernphysicskindledthesparkthatledthemtocareers
in physics. For many students, this course offers their first insights into what
physicists really do and what is exciting, perplexing, and challenging about our
profession. I hope students who use this new edition will continue to find those
inspirations.
Corvallis,Oregon KennethS.Krane
August2011 [email protected]
