Post on 07-Sep-2018
transcript
Transverse Waves
Canyouguesswhatthispictureshows?Here’sahint:theobjectsinthepicturehavebeenmagnified,andoneofthemismovingrapidly.Theobjectsareguitarstrings,andthemovingstringistheoneonthebottomright.Thestringismovingbecauseithasjustbeenplucked.Pluckingthestringgaveitenergy,whichismovingthroughthestringinamechanicalwave.Amechanicalwaveisawavethattravelsthroughmatter.Thematteramechanicalwavetravelsthroughiscalledthemedium.Thetypeofmechanicalwavepassingthroughthevibratingguitarstringisatransversewave.
What Is a Transverse Wave? Atransversewaveisawaveinwhichparticlesofthemediumvibrateatrightangles,orperpendicular,tothedirectionthatthewavetravels.Anotherexampleofatransversewaveisthewavethatpassesthrougharopewithyoushakeoneendoftheropeupanddown,asintheFigurebelow.Thedirectionofthewaveisdownthelengthoftheropeawayfromthehand.Theropeitselfmovesupanddownasthewavepassesthroughit.
Q:Whenaguitarstringisplucked,inwhatdirectiondoesthewavetravel?Inwhatdirectionsdoesthestringvibrate?A:Thewavetravelsdownthestringtotheend.Thestringvibratesupanddownatrightanglestothedirectionofthewave.Crests and Troughs Atransversewaveischaracterizedbythehighandlowpointsreachedbyparticlesofthemediumasthewavepassesthrough.Thehighpointsarecalledcrests,andthelowpointsarecalledtroughs.Youcanseebothinthefiguretotheright.
S Waves TransversewavescalledSwavesoccurduringearthquakes.Thedisturbancethatcausesanearthquakesendstransversewavesthroughundergroundrocksinalldirectionsawayfromthedisturbance.Swavesmaytravelforhundredsofmiles.AnSwaveismodeledintheFigurebelow
Summary • Atransversewaveisawaveinwhichparticlesofthemediumvibrateperpendicularto
thedirectionthatthewavetravels.• Thehighpointsofatransversewavearecalledcrests,andthelowpointsarecalled
troughs.• Swavesaretransversewavesthattravelthroughundergroundrocksduring
earthquakes. Review
1. Whatisatransversewave?2. Sketchatransversewaveandlabelthecrestsandtroughs.3. InferhowSwavesmightaffectstructuressuchasbuildings.
Longitudinal Waves You’veprobablyplayedwithSlinkyspringtoyslikethese.They’resimpletoys,buttheycanmoveinveryinterestingways.Pushinginontheendofaspringtoy,forexample,givesitenergythatmovesthroughthespringinalongitudinalwave.What Is a Longitudinal Wave? Alongitudinalwaveisatypeofmechanicalwave.Amechanicalwaveisawavethattravelsthroughmatter,calledthemedium.Inalongitudinalwave,particlesofthemediumvibrateinadirectionthatisparalleltothedirectionthatthewavetravels.YoucanseethisintheFigurebelow.Theperson’shandpushesandpullsononeendofthespring.Theenergyofthisdisturbancepassesthroughthecoilsofthespringtotheotherend.
Compressions and Rarefactions NoticeintheFigureabovethatthecoilsofthespringfirstcrowdclosertogetherandthenspreadfartherapartasthewavepassesthroughthem.Placeswhereparticlesofamediumcrowdclosertogetherarecalledcompressions,andplaceswheretheparticlesspreadfartherapartarecalledrarefactions.Themoreenergythewavehas,theclosertogethertheparticlesareincompressionsandthefartheraparttheyareinrarefactions. P Waves EarthquakescauselongitudinalwavescalledPwaves.Thedisturbancethatcausesanearthquakesendslongitudinalwavesthroughundergroundrocksinalldirectionsawayfromthedisturbance.PwavesaremodeledintheFigurebelow.Q:WherearethecompressionsandrarefactionsofthemediuminthismodelofPwaves?A:Thecompressionsaretheplaceswheretheverticallinesareclosesttogether.Therarefactionsaretheplaceswheretheverticallinesarefarthestapart.
Summary
• Alongitudinalwaveisatypeofmechanicalwave,orwavethattravelsthroughmatter,calledthemedium.Inalongitudinalwave,particlesofthemediumvibrateinadirectionthatisparalleltothedirectionthatthewavetravels.
• Placeswhereparticlesofthemediumcrowdclosertogetherarecalledcompressions.Placeswhereparticlesofthemediumspreadfartherapartarecalledrarefactions.
• EarthquakescauselongitudinalwavescalledPwaves,whichpassthroughundergroundrocks.
Review
1. Whatisalongitudinalwave?2. Drawasketchofalongitudinalwave.Usearrowstoshowthedirectionofthewaveand
thedirectionofthevibratingparticlesofthemedium.Addlabelstoidentifythecompressionsandrarefactions.
3. DescribePwaves.