Physics on Your Feet: Berkeley Graduate Exam Questions: or Ninety Minutes of Shame but a PhD for the Rest of Your Life! PDF
Preview Physics on Your Feet: Berkeley Graduate Exam Questions: or Ninety Minutes of Shame but a PhD for the Rest of Your Life!
Physics on Your Feet: Berkeley Graduate Exam Questions Physics on Your Feet: Berkeley Graduate Exam Questions or Ninety Minutes of Shame but a PhD for the Rest of Your Life! Second Edition Dmitry Budker University of California, Berkeley, USA and Johannes Gutenberg University, Mainz, Germany Alexander O. Sushkov Boston University, Boston, MA, USA Illustrated by Vasiliki Demas 1 3 GreatClarendonStreet,Oxford,OX26DP, UnitedKingdom OxfordUniversityPressisadepartmentoftheUniversityofOxford. ItfurtherstheUniversity’sobjectiveofexcellenceinresearch,scholarship, andeducationbypublishingworldwide.Oxfordisaregisteredtrademarkof OxfordUniversityPressintheUKandincertainothercountries (cid:2)c DmitryBudker,AlexanderO.Sushkov,VasilikiDemas2015,2021 Themoralrightsoftheauthorshavebeenasserted FirstEditionpublishedin2015 Impression:1 Allrightsreserved.Nopartofthispublicationmaybereproduced,storedin aretrievalsystem,ortransmitted,inanyformorbyanymeans,withoutthe priorpermissioninwritingofOxfordUniversityPress,orasexpresslypermitted bylaw,bylicenceorundertermsagreedwiththeappropriatereprographics rightsorganization.Enquiriesconcerningreproductionoutsidethescopeofthe aboveshouldbesenttotheRightsDepartment,OxfordUniversityPress,atthe addressabove Youmustnotcirculatethisworkinanyotherform andyoumustimposethissameconditiononanyacquirer PublishedintheUnitedStatesofAmericabyOxfordUniversityPress 198MadisonAvenue,NewYork,NY10016,UnitedStatesofAmerica BritishLibraryCataloguinginPublicationData Dataavailable LibraryofCongressControlNumber:2021934833 ISBN978–0–19–884236–1(hbk.) ISBN978–0–19–884237–8(pbk.) DOI:10.1093/oso/9780198842361.001.0001 Printedandboundby CPIGroup(UK)Ltd,Croydon,CR04YY LinkstothirdpartywebsitesareprovidedbyOxfordingoodfaithand forinformationonly.Oxforddisclaimsanyresponsibilityforthematerials containedinanythirdpartywebsitereferencedinthiswork. To the memory of our teacher and dear friend, Max Zolotorev (1941-2020) Preface to the Second Edition In the few years that passed from the publication of the First Edition of the book, we receivedalotofpositivefeedbackandencouragementfromourreadersandcolleagues, which has motivated us to continue keeping an eye out for good questions suitable for oral PhD exams, now also at the Johannes Gutenberg University at Mainz and BostonUniversity,therespectiveschoolswherethetwoofuscurrentlyteach(andgive examinations).Somecolleagueshaveofferedussuchquestions,and,asbefore,wehave come up with a number of “exam-style” questions ourselves. TheSecondEditionextendsthebookrathersignificantly,withnewproblemsfound towards the ends of the sections and new cartoons skillfully drawn by Dr. Vasiliki Demasaddedthroughoutthebook.Wehavealsotakentheopportunitytocorrectthe (surprisingly few) misprints and minor errors noticed in the First Edition. We hope the readers continue to find Physics on Your Feet useful and perhaps entertaining! Dmitry Budker Alex Sushkov Mainz and Boston July 2020 Preface to the First Edition How this book came about In May 2010, the Physics Department of the University of California at Berkeley where the two of us, at different times, had been Ph.D. students, abandoned the PreliminaryOralExaminations,a.k.aoralprelims,forthefirst-yeargraduatestudents, thus breaking a 60-year-long tradition. In fact, oral examinations were offered at the Berkeley Physics Department much earlier, however, their most recent format and scope more or less settled by 1950, as described by A. C. Helmholz in his History of the Physics Department. 1950–1968 (Helmholz, 2004). The Berkeley prelim was a scary experience for those of us on the “receiving end (A. S.),” and a half-day semi-annual chore for those administering the test (D. B. did this from Fall of 1995 through Spring of 2010; he “missed” taking the oral prelims as heenteredtheBerkeleyPhysicsgraduateprogramin1989asacontinuingstudent,but hashadhisshareoforalexaminationselsewhere).Nevertheless,thetwoofusstrongly feelthatthishasbeenextremelyusefulforthestudents,providingthem,perhaps,the first“real-life”scientific-communicationexperience,andgivinganopportunitytolook at the beautiful world of physics in some approximation of completeness. It has also been a truly rewarding experience for the faculty member (D. B.). One learned a lot from the brilliant students, and from the wise colleagues asking truly interestingandprofoundquestions.Someofthematerialofthisbookisdrawnfromthe notestakenbyD.B.attheexamsovertheyears,aswellasfromthequestionscollected by the students and passed as an exam-preparation aid “generation to generation.” The origin of the content of the book, therefore, has collective nature, and we are extremelygratefultothemembersoftheBerkeleyphysicsfacultywhohavegenerously allowed us to use their ideas. Unfortunately, many of our sources are no longer alive to ask for permission. We remain in deep gratitude to Profs David Judd, Gil Shapiro, Ronald Ross, and, indirectly, many others. So what’s the point of the book now that the Berkeley orals are no more? We hopethiscollectionwillbeusefultostudents(ofallagesandeverywhere)whowishto refresh and/or test their knowledge of physics, and also to students at the universities that still administer orals. And there are always written prelims, qualifying exams, even at Berkeley (at least, for now) ... The level of the readers we primarily aim at is upper-division undergraduates and first-year graduate students, although some of theseproblemswillcertainlybeenjoyedbypostdocsanddistinguishedphysicsfaculty, looking for a fun break from or an unexpected contribution to their research. We have had a lot of fun writing up the problems for this book, and we would like our readers to share this joy (rather than stress out about the upcoming exam, which isunproductive).Wearegreatlyassistedinthisbytheeye-pleasingdrawingsprepared by our skillful illustrator, Dr. Vasiliki (Vicky) Demas. viii Preface to the First Edition m v Other books There are several other collections of problems with the scope and goals partially overlapping with ours. Among these are the following. • Scattering and Structures by(PovhandRosina,2005),whichisalovelycollection of problems for the German oral Diploma and Ph.D. exams with emphasis on quantum phenomena. • AGuidetoPhysicsProblems byCahn,Mahan,andNadgorny(Cahn,Mahan,and Nadgorny,1994),whichisawonderfulcollectionofwrittenexaminationproblem, also supplied with many delightful cartoons (not to mention the most insightful physics). • An impressive multi-volume Problems and Solutions set by a group of Chinese authors (Zhang, Zhou, Zhang, and Lim, 1995; Lim, 1998; Bai, Guo, Lim, 1991; Lim, 2000) compiled by the Physics Coaching class at the University of Science and Technology in China as a guide for preparation to Ph.D. exams at major Americanuniversities.Whilethiscollectionappearstobeveryuseful,wefindthe choice of questions and style of solutions to be substantially different from our own. How to use this book ix • University of Chicago Graduate Problems in Physics, with Solutions by (Cronin, Greenberg, and Telegdi, 1967) is another great collection, although it generally appears to be more mathematical than this book (and has no cartoons!). • University of California, Berkeley, Physics Problems, with Solutions by (Chen, 1974) is a forty year-old collection of problems based on the Berkeley written Ph.D. exams. How to use this book We decided to present the solutions right after the problems, instead of separating them into a different part of the book. Nevertheless, as with all respectable problem books,itisrecommendedthatthereaderbeginsbysuppressingthetemptationtoread or peep into the solution right away, and gives the problem an honest “college try” before consulting with the solution (which may be wrong and/or inelegant, anyway). Some of the material in the solutions clearly goes beyond of what may be expected at an oralexamination.Weprovidethesediscussionsforthosereaderswhomaybeinterestedin morein-depthdetailsaboutthesubjectandmarkthecorrespondingpassagesthatcanbe omittedwithoutsacrificingthequalityofexampreparationbyplacingtheminthe“aside” environment as this paragraph. Have fun and good luck! Dmitry Budker Alexander O. Sushkov Berkeley and Harvard March 2014
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