Class Note for PH 102 with Professor Leclair at UA-Generl Physics II
Class Note for PH 102 with Professor Leclair at UA-Generl Physics II
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This 68 page Class Notes was uploaded by an elite notetaker on Friday February 6, 2015. The Class Notes belongs to a course at University of Alabama - Tuscaloosa taught by a professor in Fall. Since its upload, it has received 28 views.
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Date Created: 02/06/15
Waves Waves dis rurbance rha r pro paga res Through space iv rime usually wi rh Transfer of energy Mechanical requires a medium Eec rromagne ric no medium required Mechanical waves sound wafer seismic fhewave Elec rro magne ric waves a ligh r radio microwave infrared visible Waves fravel iv Transfer energy from place To place need no r be permanen r displacemen r eg oscilla rion abou r fixed poin r Mechanical waves require a medium i r mus r be an elas ric medium canno r be perfectly s riff or perfec rly pliable no wave 39 every rhing moves in unison all par ricles move independen rly only fra nsla rion no propaga rion Mos r waves are of Two sor rs Swing rype par rieles oscilla ring perpendicular ro propaga rion quotPensi rW rype par rieles oscilla ring parallel ro propaga rion so far as we are 00 neerned a r leas r Peseribing waves example mass on a spring oscilla rion perp ro wave diree riom waveleng rh A wave pro paga rio n gt A ampli rude im rensi ry W A wavelengfh char size Time f frequency full periodssec V waveleng rh A A oharae rerizes 39 SPATIAL varia riom feharae rerizes TIME varia rion T T Period how long per cyclequotVle TVf or fVT frequency waveleng rh veloei ry A f v velooi ry of wave propaga rion or VT A Travel one waveleng rh per period simples r wave 27r fzt Asin lt27rft 7 Charae reris ries ofwaves They have Cres rs iv Troughs in rensi ry varies periodically quotvibra rionquot Longi rudinal vibra rio us are PEKPENVICULAK 1390 propaga rion ampliTUde viva propagafiom time s rring EM waves Transverse vibra rio us are PAKALLEL ro propaga rion gtvibra rion gt propaga riom sound U W HWHHHHWHHHHI WHHWWNHHHH of course There are in be rweem eases mixed Transverse iv longitudinal eg objee rs bobbing up iv down on a wafer wave Under Typical condi rions all waves can re ee r change diree rion af rer hi r ring a re ee ring surface refrae r change diree rion af rer hi r ring a refrae ring surface diffract bend as They in rerao r wi rh objeo rs when objee r39s size is nearwaveleng rhl in rerfere superposi rion of colliding waves disperse spli r up by frequency move in a s rraigh r line propaga rion no r always ls randingl Ke ee rion pulse on a s rring demsi ry wave Kefrac rion light fr heavy s rring dcnsi ry wave at a boundary 7 20 cm Superposi rion 1 5 similarly wi rh densi ry waves Vispersion speed of wave depends on wavelengfh blue lighf waves are slower in glass fake a longer pafh A Ieleviation angle for red light visible light R O Y C B V angular dispersion wafer longer wavele quot9th Travel fasfer Refractive index n 19 Lanthcmum dense int LcISF 9 18 I K I 7 7 Dense im SF I 0 I 6 K F lint F2 Barium crown BaKJ Borosilicare crown BK 7 5 Fluorite crmm FK51A quot4 I I I I I 02 04 06 08 10 12 14 16 Wavelength A pm Piffrae rio n We39ll use This Today depends on wavelength of ligh r can use if To measure wavelengths diffraction ofa red laser projec red om ro paper disfance be rween spo rs depends on wavelemg rh observed position of line top View our experiment view lamp Through grafing we see diffraefed spol pa ern peslfion of line gives wavelengfh X 42 Y2 sinH A dsin6 observer some colors of light diffracred more than others larger angle larger wavelength more Toward blue This happens wi rh sound roo l1 ww June amide Em quotI 6 man norqu 5 311m V 31 mrbewzsemesmmd 1mm x g a would 5pm on mm X ng a am wt mesmst opening a if r g g ay lnwerea i llmumw JJ a 5 1a 7 a Dime Im l 3 m mow y a 444 919 5 3 mung almmwmnm wmwdmmmdamap m Vwmmmmmhuumaw yrs 439 57 I 1 v z y WMWBWIWW i damn punlho pimwnlwwld It nmbnahlnhdmmplm g mnwlbmmn mdlw sound null wall mm m Waugh on sound In mmnugllw hand amt u t Imam 5 If a marching band is approaching on a cross street which Instruments will you hear rst High pilched puma l l Short wavelength High pitched 1 lt A sounds and q Law pilchEd bass drum to be more mug wavelength directional because they dam di ract as much Wha r haven39f we seen Piffrae rion So rha r39s nex r week So wha r are our ligh r sources nex r week I A romic vapor discharge lamps 2 Ligh r emi r ring diodes 1 The discrefe nafure of afovnic energy levels means fhaf excifed afovns only give off speci c colors of light 2 Ligln energy confrolled by speci c single energy fransifion S rraigh r line propaga rion waves quoteaW Travel in a s rraigh r line bu r They need no r s randing waves Nodes T Amino Iles S randing waves mus r mee r special condi rioms Posi rion Natl geomefrv aries in Time T Aminodes 4 l A for end poim rs To be xed 7 L we will comeback To This V0 ppler Effee r moving rela rive ro waves I m IVW MINI Ml Sound mom 1 bum a bum NVV I J71 car traveling V hunter 1 mam ma gm obnorver 2 ELEQSW n in one period T you move closer ro fhe source by VJ fhe waves appear squashed foge rher rhe apparen r frequency VT is s rill velooi ry wavelemg rh approaching The source 2 2 2 2 f AivsT vfivsT vfivsf 117115t Approaching fhe source f i U f pi rch freq seems higher 7 v 7 Us Moving away from source f i U f pi rch freq seems lower 7 v Us Only has To do wi rh KELATIVE mo rion eg ambulance driver hears no change similarly doesn39f ma r rer who is moving happens for ligh r roo receding galaxies have quotred shif r lower freq Via rela rivi ry if works wi rh ligh r roo Ifthis bumper sticker is blue you39re driving too fast Sound in air mos r sound waves produced by vibra rio ns of a ma rerial eg gui rar s rring saxophone reed column ofair original vibra rion s rimula res a larger one sounding board sound compression rarefao rion waves in a medium Vensi ry Waves Fwducllu ornatandlng wave In aquot ulr comm Involves re exAlana fmm im we Gl sad and and Ma 00811 and 01 the column Air dispiacemenl M Messwa Open enu lollnsed and is panama n messquotfe A N A N A A N A N m No phase change upam 130 phase change 117nm quotinaction since the wave rmleclion sinus mm mm encnmlers a guaaer mums a emf email awus e mpedavma lmpedannaThis phase change Is assumed Wllh enaigy loss as sound energy Ts transnan o the Outside air MAX pressure MIN veloei ry Sound carries ENEKGY in densi ry waves pressure modula rion P FA FdAd WV energVJvoluvne varia rion of pressure varia rion of energy densi ry sound M energy rivne sound in rensi ry poweruni r area 1 11802 N pressure2 intensity N sphem area Intenslly at 41w2 surface of sphere source power P The energy twlce as an 1mm me solice Is spreiw we mr times the area hance aneislourm the Intensin 3 our hearing max iv min pressures differ by a MILLION fimes maxmin power differs by a million Times sound infensi ry covers a huge range use a log scale 2010g power goes as pressure squared power dB 7 pressure reference reference reference pressure 20 uPa Tiny a rmosphere 01325 Pa l Pa 1 Wm2 pressure differenoewould be 94 dB Snurce of sound Nucrear Weapon exp csinn 1853 Krakaloa eruption Slun gronaaes rocket launch equipment acoustic tests rnresnovo a porn neanng damage during shunterm anecr 19 engrne 100 m dislam jackhammev 1 m dislanllmsmmequa neanng damage from IongIerm exposure name noise on major road 10 rn drsranr moving auromooue 10 rn drslanl TV sor lypica hum level 1 m ais1anr norma taming I rn drsran Very carm mom quiet rusuing leaves cann human blealmng audmury threshom a12 kHz undamaged human ears RMS sound pressure sauna pressure level F3 or re 20 pPaI approx 240 approx 160 a 100 miles 170430 approx was 100 m an approx 20 6 200 mm 40 2 approx mo 05 approx as 02 05 00 90 00202 60 30 002 approx so 00024302 4H0 00002 00005 20 30 000005 10 000002 0 Sound lcvsl 3 lt13 Inrmsnnic Sonic Ullrasonic frequencies frequencies frequencies 220 200 l 80 160 MO I 20 Car horn l N lt gt Motorcycle School cafe Urban Lra ir 51mm Birds lt J gt Ionverszuion Whispcrrrl sprerh 100 l 001 10 000 100 00 ummbuh F cqucncyHz Sound um I 113 Infmsnnic frequencies 220 200 l 80 160 l 40 20 100 Sn nic rrequencies Rock concert Motorcycle Urban tram Cur horn Conve rsaui on Slmul Birds lt J gt Whispcrm sprcch 100 l 100 10 000 Ulu39ason ic Frequencies gt School Hzr lt gt 100 0 FrequencyHz Speaker cone forces surrounding air ro compressrarer moves by induc rion cone pushes nearby air molecules which hit o rhers 1 g can use The opposi re fora microphone sound in vibra res coil in magme r Time changing ux induces vol rage vol rage can be ampli ed used To drive a speaker How To iransvni r sound in a medium mus r have a degree of ELASTITCITY ie a res roring force Solids bonds are like springs a rovns respond To each o rher39s vno rions speed of sound lt gt orys ral s rruo rure bonding bond s rreng rh lt gt speed of sound Liquids also rrue bu r less so Gasses like air quotres roring force crea rion of par rial vacuum lower pressure region air moves in To fill void Horribly inefficien r Vepends on PRESSURE of gas Pepends on WHAT GAS vacuum eg space no rhing There ro compressexpand solid in vacuum s rill 0K Kesul r sound is really slow in air Medium u nus fas rer in Warm air06 ms perm Gm Hydrogcn mm L 286 mum NC 972 Humid air sligh rly 1143 I A 331 abou r one MILLIONTH high speed ow web m Liquids a125 C i JIM I 333 Wamr I 4939 Mercury eg golf ball sfruek 500m away Swivelquot I 1 Cm bxmirimrhlmidu 92H ligh r 6139 Sumquot N Pm IN 5mm 6tlight 16Msec hiquot C Aluminum G 420 But 4 71M sound Copper 30m 6x Cnld 3244 6tsound Q sec Lucite 2mm lcdd I My mS Rubber I my Sound can be KEFLEGTEV like o rher waves Keverbera rion differen r pa rhs from source ro observer are possible sligh r difference in pa rh leng rh rime lag Yuck For good sound This effeo r mus r be op rimized walls foo re eo rive reverb problems walls roo re eo rive dead sound low level re eo red sound lively iv full like in The shower Bes r parabolic or ellip rioal re eo ror aka quotwhispering gallery parabolic or ellip rieal room St Paul39s ea rhedml London can hear a whisper across fhe room Secondary Focal Point Primary 5 Focal Point KefraoTion of sound As a my cal mTIs mm a 39FW 55 1quot 33g muwmcm mom Mam 4 Magnum mumps n 5 WWW memes Mmmmm Mum w ammo smmsdmm 13 Av w a new Smdmm quot 5 szuahza ons mm omenacuon e I A u N Fas Concrete Swamp If The air above The earTh is warmer Than ThaT aT The surface sound will be benT back downward Toward The surface by refraoTion Wanner in mllllllllm Mdni 1 one 0 mm Ea Vigil of layff remainm 61 9 source kit Direct sound path ll III Illlllllllllllaslistener Normally only fhe direo r sound is received Kefrao rion can add some addi rional sound Effeo rively ampli es The sound Na rural ampli ers can occur over cool lakes Na rural resonance frequencies objeo rs have oharao reris rie vibra rion modes unique sounds oomposi rion shape densi ry elas rioi ry lt depends on all These Nudes eg s rring TM 7 L 2 I Anu nn dun geome rry dio ra res allowed frequencies fundamental over rones harmonies A Ln and Afv gtL gui rar s rrings fre rs change L wha r is fhe velooh y v 1 Velooi ry is rela red in T v i T Tension force p u mass per uni r leng rh weigh r s rring fixed a r bo rh ends change Lvia FKETS shor rer higher pi reh rune via TENSION righ rer higher pi reh range via MASS rhinner higher pi reh same deal for a piano less The fre rs lt gt fundamen ral WU cXJ 7R i a 15over rone 2quot harmonic n2 lt3ltgtltgt 339 harmo mic W3 eltgtOltgt 4 harmonic W4 Ogtltgtltgtltgt ltgtkfgtcltgtltgtltgt mylt3 if is differen r if ends are quotof fixed example air columns pipe organ we can se r up resonance in a xed rube ofair pipe open a r bo rh ends 555 STAMPING WAVES se r up in rube need nodes a r The ends max veloei ry zero pressure difference mafh same as for fhe s rring v 340 ms for air a r KT Things are differen r when we close one end offhe pipe 5 A A airveloei ry is ZEKO a r one end effeo rively Twice as long pi roh is Twice as low TL U f now n mus r be 0W for waves To t v I I I I I I I I I I I I I I I I I I I OPEN OPEN pipes like s rrings all harmonies presen r OPEN CLOSE pipes only 0W harmonies 2x lower pi reh presence or absence of harmonies changes quotTo me waveform sum of fundamen ral harmonies Fundamemal mus sinmvu Hus vovava 3m harmomc EHua s Harmamcany dismned waveform e A clarinet is GLOSEV on one end only odd harmonies quotwarm 5 dark compared To saxophone all harmonics Clarinet u 3 Clarmet 0 m Amplltude 4 A i Amplitude 53 o 5 1o 15 Time milliseconds 4 2nd Hamwnic lt7 4th Hannonic DD 0 500 mm 1500 Frequency Hz PURE SOUND Pi roh and frequency Ratio Fundamental Freq mas idenmylas oclave Harman Mu lple a Menu Common Name Example I Fundamemal A2 HDHZ x 2 Octave A 220 Hz 2X 3 Penem an Ea 330 Hz max 4 Ocvave A4 440 Hz 4X 5 MamrTmrd 25 7 550 Hz 5 5 Penem an E 4 A 660 H1 5 7 Perfecl Sevenmquot 74 770 Hz 7x a Ocvave aao H1 BX 111 Ix 212Xals122 m 3215 4I22xalsax 54L25x 64l5x 7Al75x 942xalsaxx Whaiaboufa runing fork or any 3V solid iii wavelengths in each dimension 390 l m n a l m n are integers Aluminum v 4900ms say I x l x 05cm block f 3500 Hz A7 3 octaves above middle 0 In rerference fwo sound waves of differenf frequencies al rernafing consfruc rive and desfrucfive inferference causes The sound f0 quotbea rquot bea r frequency difference in frequency of The Two waves Is this cammive or mummy Inlelfelem e f L f U H U bea rs bea rs sweep one genera ror sweep one genera ror
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