英文高中物理1：声波的性质和公式WaveProp课件

PHY12

2013Term1Week1:WavePropertiesandEquationsPHY12

2013Term1Week1:Whatisawave?Spreadingofdisturbancefromoneplacetoanother.Thesourceisavibrationoroscillation.EnergyistransferredfromonepointtoanotherWITHOUTphysicaltransferofanymaterialbetweenthetwopointsWhatisawave?SpreadingofdiGeneraldefinitionsofvibrationsandwavesVibration:inageneralsense,anythingthatswitchesbackandforth,toandfro,sidetoside,inandout,offandon,loudandsoft,orupanddownisvibrating.Avibrationisawiggleintime.Wave:awiggleinbothspaceandtimeisawave.Awaveextendsfromoneplacetoanother.Vibrationsandwaves:thesourceofallwavesissomethingthatisvibrating.Wavesarepropagationsofvibrationsthroughoutspace.GeneraldefinitionsofvibratiVIBRATIONOFAPENDULUMWhatdoestheperiod(T)dependupon?Lengthofthependulum(l).Accelerationduetogravity(g).Perioddoesnotdependuponthebobmassortheamplitudeoftheswing.Vibrationofapendulum.Theto-and-frovibratorymotionisalsocalledoscillatorymotion(oroscillation).VIBRATIONOFAPENDULUMWhatdoWhenoscillationsaresmall,themotioniscalledsimpleharmonicmotion(shm)andcanbedescribedbyasimplesinecurve.英文高中物理1：声波的性质和公式WaveProp课件CrestsandTroughsCrests:pointsofmaximumdisplacementonawaveTroughs:pointsofminimumdisplacementonawaveDistancealongropedisplacementCRESTCRESTTROUGHCrestsandTroughsCrests:poinWaveProperties

Amplitude Amplitudeistheheightofthewaveaboveor belowtheequilibriumpoint.WaveProperties

Amplitude AmpAMPLITUDE(A)MaximumDisplacementfromtherestorcentralposition.SIunitmetre(m)displacementdistancealongropecrestcresttroughamplitudeamplitudeAMPLITUDE(A)MaximumDisplacemWaveProperties

Wavelength Wavelength,l,isthedistancebetweentwo consecutivepeaks.WaveProperties

Wavelength WaWavelength(λ)Thedistancebetweentwosuccessivepointsofthesamephase.Example:distancebetweentwocrests.SIunit:metre(m).displacementdistancealongropecrestcresttroughλamplitudeamplitudeWavelength(λ)ThedistancebetWaveProperties

Frequency

Frequency,f,isthenumberofwavespassingaparticularpointinonesecond.WaveProperties

Frequency FreqFrequency(f)Numberofcompletewavesgeneratedpersecond(ornumberofcycles/oscillationspersecond)SIunit:hertz(Hz)Frequency(f)NumberofcompletWaveProperties

PeriodThewaveperiod,P,thisthetimeittakeonewavetopasstheobserver.WaveProperties

PeriodThewavePeriod(T)Timetakentogenerateonecompletewave(ortocompleteonecycle)SIunit:second(s)Period(T)TimetakentogeneraExamplesofFrequencyWhatisthefrequencyofthesecondhandofaclock?Frequency=1cycle/60sec Period=60secWhatisthefrequencyofUSPresidentialelections?Frequency=1election/4yrs Period=4yrsExamplesofFrequencyWhatistAsfincreases,TdecreasesRelationshipbetweenTandfAsfincreases,TdecreasesRelPuttingeverythingtogetherTrythis!

PuttingeverythingtogetherTryThink…Inspacefilms,weoftenhearthesoundoftheengineofthespaceshipasthezoompasteachotherinouterspace.Weevenhearthespaceshipfiringlasersatoneanother.Whatisseriouslywronginthefilms?Think…Inspacefilms,weoftenThink…Whydon'tincomingoceanwavesbringmorewaterontotheshoreuntilthebeachiscompletelysubmerged?Think…Whydon'tincomingoceanThink…Howwillthemotionofwaterwaveschangeastheymovefromdeeptoshallowwater?Howaboutfromshallowtodeepwater? (Hint:Considerthespeedofthewaves)Think…HowwillthemotionofwWaveMotion,Speed,TypeWavestotransferenergy,notmatter,fromoneplacetoanotherAVibratingsourcetransfersadisturbanceSpeeddependsontypeofvibratingsourceandmediumthroughwhichittravelsWavespeed=fx

Thesametypeofwavemovesatthesamespeedregardlessoff

or

Foranywave,fisinverselyproportional

to

WaveMotion,Speed,TypeWaves06/10/2023TheWaveEquationThewaveequationrelatesthespeedofthewavetoitsfrequencyandwavelength:Wavespeed(v)=frequency(f)xwavelength()

inms-1 inHz inmV

f02/08/2023TheWaveEquationThe06/10/2023Awaterwavehasafrequencyof2Hzandawavelengthof0.3m.Howfastisitmoving?Awaterwavetravelsthroughapondwithaspeedof1ms-1andafrequencyof5Hz.Whatisthewavelengthofthewaves?Thespeedofsoundis330ms-1(inair).WhenDavehearsthissoundhisearvibrates660timesasecond.Whatwasthewavelengthofthesound?Purplelighthasawavelengthofaround6x10-7mandafrequencyof5x1014Hz.Whatisthespeedofpurplelight?Someexamplewaveequationquestions0.2m0.5m0.6ms-13x108ms-102/08/2023AwaterwavehasafWaveTypesTransversewavesvibrateacrossfromdirectionoftravelLongitudinalwavesvibratealongthedirectionoftravel(asinaspring)WaveTypesTransversewavesvib06/10/2023Transversevs.longitudinalwavesTransversewavesarewhenthedisplacementisatrightanglestothedirectionofthewave…Longitudinalwavesarewhenthedisplacementisparalleltothedirectionofthewave…DisplacementDirectionDirectionDisplacementWherearethecompressionsandrarefactions?02/08/2023Transversevs.longiSoundWavesMoleculesintheairvibrateabout