没有幻灯片标题-哈尔滨工程大学物理实验教学中心

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1、DeterminingtheVelocityofSoundandUsingtheOscilloscope1.Purpose:UnderstandtherelationshipbetweenthesoundspeedandtheairstateparametersUnderstandthefunctionofthepiezoelectricitytransducer.UnderstanddeeplythetheoryofstandingwavesandvibratinginterferingMasteringtheusingoft

2、heoscilloscope.Masteringamethodofmeasuringsoundspeed.2.Principle:(1)soundspeedintheoryisexpressedas(1)Intheformula(1),T0=273.15K，tisconditiontemperature,formula(1)canbeusedtocalculatethesoundspeedinair.(2)thetheoryofsoundspeedmeasuringBytherelationshipbetweenspeedvfr

3、equencyfandwavelengthλ:v=fλ(2)sowhenwemeasureoutfandλ,wecancalculatevbyformula(2).TheinstrumentsareshowedinFig.1.Fig.1InstrumentsusedtomeasureλThetransducerS1isusedtoemitsoundwave.ThetransducerS2isusedtoreceivesoundwave.Whenthestandingwaveappears,thesoundwavereceived

4、byS2isstrongest,andthephenomenacanbedisplacedbytheoscilloscope.Astandingwavepatternisaninterferencephenomenon.Itisformedastheresultoftheperfectlytimedinterferenceoftwowavespassingthroughthesamemedium.Astandingwavepatternisnotactuallyawave;ratheritisthepatternresultin

5、gfromthepresenceoftwowavesofthesamefrequencywithdifferentdirectionsoftravelwithinthesamemedium.Onecharacteristicofeverystandingwavepatternisthattherearepointsalongthemediumwhichappeartobestandingstill.Thesepoints,sometimesdescribedaspointsofnodisplacement,arereferred

6、toasnodes.Thereareotherpointsalongthemediumwhichundergovibrationsbetweenalargepositiveandlargenegativedisplacement.Thesearethepointswhichundergothemaximumdisplacementduringeachvibrationalcycleofthestandingwave.Inasense,thesepointsaretheoppositeofnodes,andsotheyarecal

7、ledantinodes.Astandingwavepatternalwaysconsistsofanalternatingpatternofnodesandantinodes.Theanimationshownbelowdepictsaropevibratingwithastandingwavepattern.Thenodesandantinodesarelabeledonthediagram.Whenastandingwavepatternisestablishedinamedium,thenodesandtheantino

8、desarealwayslocatedatthesamepositionalongthemedium;theyarestandingstill.Itisthischaracteristicwhichhasearnedthepatternthenamestandi