通信及基础工程4

Unit1TextBBiographyofHeinrichHertzBiographyofHeinrichHertz1InaseriesofbrilliantexperimentsHeinrichHertzdiscoveredradiowavesandestablishedthatJamesClerkMaxwell’stheoryofelectromagnetismiscorrect.Hertzalsodiscoveredthephotoelectriceffect2,providingoneofthefirstcluestotheexistenceofthequantumworld.Theunitoffrequency,thehertz,isnamedinhishonor.TextTextWordsNotesDiscussionHome1.SchoolAgedsix,HeinrichbeganattheDr.WichardLangeSchoolinHamburg.ThiswasaprivateschoolforboysrunbythefamouseducatorFriedrichWichardLange.Theschooloperatedwithoutreligiousinfluence;itusedchild-centeredteachingmethods,takingaccountofstudents‘individualdifferences.Itwasalsostrict;thestudentswereexpectedtoworkhardandcompetewithoneanothertobetopoftheclass.Heinrichenjoyedhistimeatschool,andindeedwastopofhisclass.(tobecontinued)TextTextWordsNotesDiscussionHome(Continued)Unusually,Dr.Lange’sschooldidnotteachGreekandLatin–theclassics–neededforuniversityentry.TheveryyoungHeinrichhadtoldhisparentshewantedtobecomeanengineer.Whentheylookedforaschoolforhim,theydecidedthatDr.Lange’salternativefocus,whichincludedthesciences,wasthebestoption.TextWordsNotesDiscussionHomeHeinrich'smotherwasespeciallypassionateabouthiseducation.Realizinghehadanaturaltalentformakingthingsandfordrawing,shearrangeddraftsmanshiplessonsforhimonSundaysatatechnicalcollege.Hestartedtheseaged11.TextTextWordsNotesDiscussionHome2.HomeschoolandBuildingScientificApparatusAged15,HeinrichleftDr.Lange'sschooltobeeducatedathome.Hehaddecidedthatperhapshewouldliketogotouniversityafterall.NowhereceivedtutoringinGreekandLatintopreparehimfortheexams.TextTextWordsNotesDiscussionHomeHeexcelledatlanguages,agiftheseemstohaveinheritedfromhisfather.ProfessorRedslob,alanguagespecialistwhogaveHeinrichsometuitioninArabic,advisedhisfatherthatHeinrichshouldbecomeastudentoforientallanguages.Neverbeforehadhemetanyonewithgreaternaturaltalent.TextTextWordsNotesDiscussionHomeHeinrichalsobeganstudyingthesciencesandmathematicsathome,againwiththehelpofaprivatetutor.Hehadacolossalappetiteforhardwork.Hismothersaid:Whenhesatwithhisbooksnothingcoulddisturbhimordrawhimawayfromthem.TextTextWordsNotesDiscussionHomeAlthoughhehadlefthisnormalschool,hecontinuedattendingthetechnicalcollegeonSundaymornings.Intheeveningsheworkedwithhishands.Helearnedtooperatealathe.Hebuiltmodels,andthenbeganconstructingincreasinglysophisticatedscientificapparatus,suchasaspectroscope.Heusedthisapparatustodohisownphysicsandchemistryexperiments.TextTextWordsNotesDiscussionHome3.BecomingaScientist(1)PhysicsinMunichInspring1876,aged19,hemovedagain,toDresden,tostudyengineering.Afteronlyafewmonthshewasdraftedintothearmyforayear’scompulsoryservice.Aftercompletinghisarmyservice,the20-year-oldHertzmovedtoMunichtobeginanengineeringcourseinOctober1877.Amonthlater,aftermuchinternalanguish,hedroppedoutofthecourse.Hehaddecidedthataboveallelsehewantedtobecomeaphysicist.(Tobecontinued)TextWordsNotesDiscussionHome(Continued)HeenrolledattheUniversityofMunich,choosingcoursesinadvancedmathematicsandmechanics,experimentalphysics,andexperimentalchemistry.AfterasuccessfulyearatMunichhemovedtotheUniversityofBerlinbecauseithadbetterphysicslaboratoriesthanMunich.TextTextWordsNotesDiscussionHome(2)Berlin,Helmholtz,andRecognitionInBerlin,aged21,HertzbeganworkinginthelaboratoriesofthegreatphysicistHermannvonHelmholtz.HelmholtzmusthaverecognizedararetalentinHertz,immediatelyaskinghimtoworkonaproblemwhosesolutionhewasparticularlyinterestedin.TheproblemwasthesubjectofafiercedebatebetweenHelmholtzandanotherphysicistbythenameofWilhelmWeber.TextTextWordsNotesDiscussionHomeTheUniversityofBerlin'sPhilosophyDepartment,withHelmholtz'sencouragement,hadofferedaprizetoanyonewhocouldsolvetheproblem:Doeselectricitymovewithinertia?Alternatively,wecouldframethequestionintheform:Doeselectriccurrenthavemass?Or,asframedbyHertz:Doeselectriccurrenthavekineticenergy?TextTextWordsNotesDiscussionHomeHertzstartedworkontheproblemandquicklyfellintoapleasantroutine:attendingalectureeachmorningineitheranalyticaldynamicsorelectricity&magnetism,carryingoutexperimentsinthelaboratoryuntil4pm,thenreading,calculating,andthinkingintheevening.HepersonallydesignedexperimentswhichhethoughtwouldanswerHelmholtz'squestion.Hebegantoreallyenjoyhimself,writinghome:TextTextWordsNotesDiscussionHomeTextTextWordsNotesDiscussionHome4.ThePrizeInAugust1879,aged22,Hertzwontheprize–agoldmedal.Inaseriesofhighlysensitiveexperimentshehaddemonstratedthatifelectriccurrenthasanymassatall,itmustbeincrediblysmall.WehavetobearinmindthatwhenHertzcarriedoutthisworktheelectron–thecarrierofelectriccurrent–hadnotevenbeendiscovered.J.J.Thomson’sdiscoverywasmadein1897,18yearsafterHertz’swork.TextTextWordsNotesDiscussionHomeOtherphysicistsbegantonoticejusthowdazzlingHertz'sworkhadbeen-theyoungstudenthadputtogetherexperimentsattheforefrontofphysics,personallymodifyingapparatusasneeded.Hispracticalskills,developedathomeintheevenings,wereprovingtobepriceless.Hisprize-winningworkwaspublishedintheprestigiousjournalAnnalenderPhysik.TextTextWordsNotesDiscussionHomeRecognizingtheincredibletalenthehadinhislaboratory,HelmholtznowaskedHertztocompeteforaprizeofferedbytheBerlinAcademy:verifyingJamesClerkMaxwell'stheoryofelectromagnetism.Maxwellhadstatedin1864thatlightwasanelectromagneticwaveandthatothertypesofelectromagneticwavecouldexist.TextTextWordsNotesDiscussionHome5.DoctorofPhysicsHertzdeclinedthisproject;hebelievedtheattempt,withnoguaranteeofsuccess,wouldtakeseveralyearsofwork.Hewasambitiousandwantedtopublishnewresultsquicklytoestablishhisreputation.TextTextWordsNotesDiscussionHomeInsteadofworkingfortheprize,hecarriedoutamasterfulthree-monthprojectonelectromagneticinduction.Hewrotethisupasathesis.InFebruary1880,attheageof23,histhesisbroughthimtheawardofadoctorateinphysics.Helmholtzquicklyappointedhimasanassistantprofessor.LaterthatyearHertzwrote:TextTextWordsNotesDiscussionHomeTextTextWordsNotesDiscussionHomeHertzstayedinHelmholtz'slaboratoryuntil1883,duringwhichtimehepublished15papersinacademicjournals.TextTextWordsNotesDiscussionHome6.MathematicalPhysicsatKielHertzwasagiftedexperimentalphysicist,butcompetitiontosecurealectureshipatBerlinwashigh.Instead,withHelmholtz'ssupport,HertzbecamealecturerinmathematicalphysicsattheUniversityofKiel.Thisposition,theoreticalratherthanexperimental,extendedhisabilities.AtKielhebegantogettogripswithMaxwell'sequations,writinginhisdiary:TextTextWordsNotesDiscussionHomeTextTextWordsNotesDiscussionHomeTheresultofHertz'sworkwasahighlyregardedpapercomparingMaxwell'selectromagnetictheorywithcompetingtheories.HeconcludedthatMaxwell'stheorylookedthemostpromising.InfacthereworkedMaxwell'sequationsintoamoreconvenientform.TextTextWordsNotesDiscussionHomeHelaterwrote:TextTextWordsNotesDiscussionHome7.TheDiscoveryofRadioWaves(1)Well-EquippedLaboratoriesandAttackingtheGreatestProblemInMarch1885,desperatetoreturntoexperimentalphysics,HertzmovedtotheUniversityofKarlsruhe.Aged28,hehadsecuredafullprofessorship.Hewasactuallyofferedtwootherfullprofessorships,asignofhisflourishingreputation.HechoseKarlsruhebecauseithadthebestlaboratoryfacilities.TextTextWordsNotesDiscussionHomeWonderingaboutwhichdirectionhisresearchshouldtake,histhoughtsdriftedtotheprizeworkHelmholtzhadfailedtopersuadehimtodosixyearsearlier:provingMaxwell'stheorybyexperiment.HertzdecidedthatthismightyundertakingwouldbethefocusofhisresearchatKarlsruhe.TextTextWordsNotesDiscussionHome(2)ASparkthatChangedEverythingAftersomemonthsofexperimentaltrials,theapparentlyunbreakablewallsthathadfrustratedallattemptstoproveMaxwell'stheorybegancrumbling.ItstartedwithachanceobservationearlyinOctober1886,whenHertzwasshowingstudentselectricsparks.Hertzbeganthinkingdeeplyaboutsparksandtheireffectsinelectriccircuits.Hebeganaseriesofexperiments,generatingsparksindifferentways.TextTextWordsNotesDiscussionHomeHediscoveredsomethingamazing.Sparkswereproducingaregularelectricalvibrationwithintheelectricwirestheyjumpedbetween.ThevibrationmovedbackandforthmoreofteneverysecondthananythingHertzhadeverencounteredbeforeinhiselectricalwork.Heknewthevibrationwasmadeupofrapidlyacceleratinganddeceleratingelectriccharges.IfMaxwell'stheorywereright,thesechargeswouldradiateelectromagneticwaveswhichwouldpassthroughairjustaslightdoes.TextTextWordsNotesDiscussionHome8.ProducingandDetectingRadioWavesInNovember1886Hertzconstructedtheapparatusshownbelow.TextTextWordsNotesDiscussionHomeHeappliedhighvoltagea.c.electricityacrossthecentralspark-gap,creatingsparks.Thesparkscausedviolentpulsesofelectriccurrentwithinthecopperwires.Thesepulsesreverberatedwithinthewires,surgingbackandforthatarateofroughly100millionpersecond.TextTextWordsNotesDiscussionHomeAsMaxwellhadpredicted,theoscillatingelectricchargesproducedelectromagneticwaves-radiowaves-whichspreadoutthroughtheairaroundthewires.Someofthewavesreachedaloopofcopperwire1.5metersaway,producingsurgesofelectriccurrentwithinit.Thesesurgescausedsparkstojumpacrossaspark-gapintheloop.Thiswasanexperimentaltriumph.Hertzhadproducedanddetectedradiowaves.Hehadpassedelectricalenergythroughtheairfromonedevicetoanotheronelocatedoverameteraway.Noconnectingwireswereneeded.TextTextWordsNotesDiscussionHomeTextTextWordsNotesDiscussionHome9.TakingitFurtherOverthenextthreeyears,inaseriesofbrilliantexperiments,HertzfullyverifiedMaxwell'stheory.Heprovedbeyonddoubtthathisapparatuswasproducingelectromagneticwaves,demonstratingthattheenergyradiatingfromhiselectricaloscillatorscouldbereflected,refracted,produceinterferencepatterns,andproducestandingwavesjustlikelight.TextTextWordsNotesDiscussionHomeHertz'sexperiment'sprovedthatradiowavesandlightwaveswerepartofthesamefamily,whichtodaywecalltheelectromagneticspectrum.Strangely,though,Hertzdidnotappreciatethemonumentalpracticalimportanceoftheelectromagneticwaveshehadproduced.TextTextWordsNotesDiscussionHomeThiswasbecauseHertzwasoneofthepurestofpurescientists.HewasinterestedonlyindesigningexperimentstoenticeNaturetorevealitsmysteriestohim.Oncehehadachievedthis,hewouldmoveon,leavinganypracticalapplicationsforotherstoexploit.TextTextWordsNotesDiscussionHomeThewavesHertzfirstgeneratedinNovember1886quicklychangedtheworld.By1896GuglielmoMarconi3hadappliedforapatentforwirelesscommunications.By1901hehadtransmittedawirelesssignalacrosstheAtlanticOceanfromBritaintoCanada.Hertz'sdiscoverywasthefoundationstoneformuchofourmoderncommunicationstechnology.Radio,television,satellitecommunications,andmobilephonesallrelyonit.Evenmicrowaveovensuseelectromagneticwaves:thewavespenetratethefood,heatingitquicklyfromtheinside.TextTextWordsNotesDiscussionHomeOurabilitytodetectradiowaveshasalsotransformedthescienceofastronomy.Radioastronomyhasallowedusto'see'featureswecan'tseeinthevisiblepartofthespectrum.Andbecauselightningemitsradiowaves,wecanevenlistentolightningstormsonJupiterandSaturn.Scientistsandnon-scientistsalikeowealottoHeinrichHertz.TextTextWordsNotesDiscussionHomeelectromagnetismn.[电磁]

电磁学quantumn.量子论；额excelvt.超过；擅长colossaladj.巨大的；非常的lathevt.&n.用车床加；车床，机床spectroscopen.[光]分光镜WordsWordsTextWordsNotesDiscussionHomeapparatus

n.装置，设备；仪器；器官fierceadj.凶猛的；猛烈的；暴躁的inertian.[力]惯性；惰性，迟钝；不活动dazzlen.&v.灿烂；使……目眩，炫耀gripn.&v.紧握；紧握，抓住mightyadj.&adv.&n.有力的；很，非常；有势力的人WordsTextWordsNotesDiscussionHomecrumblev.&n.崩溃，破碎；面包屑vibrationn.振动；犹豫；心灵感应radiatev..辐射；传播oscillatingadj.[物]振荡的astronomyn.天文学WordsTextWordsNotesDiscussionHome[1]

HeinrichHertz：海因里希·鲁道夫·赫兹（HeinrichRudolfHertz，1857-1894年），德国物理学家，于1888年首先证实了电磁波的存在。对电磁学有很大的贡献，频率的国际单位制单位赫兹以他的名字命名。TextWordsNotesDiscussionNotesHome[2]

ThePhotoelectricEffect：光电效应是物理学中一个重要而神奇的现象。在高于某特定频率的电磁波照射下，某些物质内部的电子会被光子激发出来而形成电流，即光生电。光电现象由德国物理学家赫兹于1887年发现，而正确的解释为爱因斯坦所提出。科学家们在研究光电效应的过程中，物理学者对光子的量子性质有了更加深入的了解，这对波粒二象性概念的提出有重大影响。TextWordsNotesDiscussionHome[3]GuglielmoMarconi：古列尔莫·马可尼（GuglielmoMarconi，1874年-1937），男，1874年4月25日生于博洛尼亚，意大利工程师，专门从事无线电设备的研制和改进；1909年诺贝尔物理学奖得主，被称为“无线电之父”。TextWord