Basic Physics III Lecture 8
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Formal Metadata
Title 
Basic Physics III Lecture 8

Title of Series  
Part Number 
8

Number of Parts 
26

Author 

License 
CC Attribution  ShareAlike 3.0 Unported:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal and noncommercial purpose as long as the work is attributed to the author in the manner specified by the author or licensor and the work or content is shared also in adapted form only under the conditions of this license. 
DOI  
Publisher 
University of California Irvine (UCI)

Release Date 
2013

Language 
English

Content Metadata
Subject Area 
00:00
Ruler
Interference (wave propagation)
Brillouin zone
Sound
Transmission line
Sunlight
Scouting
Year
Amplitude
Summer (George Winston album)
Order and disorder (physics)
Negativer Widerstand
Cosmic distance ladder
Multiplizität
Bird vocalization
Separation process
Interference (wave propagation)
Wavelength
Solid
Roll forming
Microwave
Packaging and labeling
Spare part
Tool
Defecation
Typesetting
Speckle imaging
Stock (firearms)
Power (physics)
Loudspeaker
Blanking and piercing
Metre
Fuel
Bügeleisen
Audio frequency
Monday
Sizing
Interference (wave propagation)
Cartridge (firearms)
Fahrgeschwindigkeit
Signal (electrical engineering)
Joint
Spare part
Caliber
Microwave
Envelope
08:41
DopplerVerschiebung
Sound
Effects unit
Optical amplifier
Printing press
Interstellar medium
Particle physics
Source (album)
Fire apparatus
Cosmic distance ladder
Ring strain
Bird vocalization
Wavelength
Measuring instrument
String theory
Orbital period
Spare part
Crest factor
Bending (metalworking)
Source (album)
Flight
Audio frequency
Electric guitar
Cartridge (firearms)
Caliber
June
Envelope
Microwave
14:30
Ranking
Prozessleittechnik
DopplerVerschiebung
Smart meter
Hull (watercraft)
Year
Source (album)
Wavelength
Casting
Automobile
Orbital period
Spare part
Goldsmith
Speed of sound
Zirkulator
Truck
Winter
Faraday cage
Cold inflation pressure
Source (album)
FACTS (newspaper)
Car dealership
Audio frequency
Direct current
Fahrgeschwindigkeit
Cartridge (firearms)
Siren
Caliber
Microwave
18:13
Theory of relativity
Ruler
Pooltype reactor
Sound
Effects unit
DopplerVerschiebung
Year
Interstellar medium
Source (album)
Source (album)
Bird vocalization
Audio frequency
Wavelength
Interstellar medium
Cartridge (firearms)
Continuous track
Fahrgeschwindigkeit
Electronic media
Lorentz ether theory
21:57
Prozessleittechnik
Physicist
Effects unit
Sonic boom
Radar
Minute
Source (album)
Multiplizität
Fighter aircraft
Bird vocalization
Roll forming
Wavelength
Gun
Hitzeschild
Speed of sound
Measurement
Crest factor
Speckle imaging
Jet (brand)
Sensor
Sound
Source (album)
FACTS (newspaper)
Direct current
Cartridge (firearms)
Fahrgeschwindigkeit
Siren
Motorjacht
Mintmade errors
Food storage
Plane (tool)
Large Hadron Collider
Microwave
Shock absorber
Jet (lignite)
Sound
DopplerVerschiebung
Schubvektorsteuerung
Ink
Printing press
Crystal structure
Particle physics
Reflexionskoeffizient
Weather front
Fahrgeschwindigkeit
Volumetric flow rate
Automobile
Spare part
Shock wave
Brigantine
Intensity (physics)
Sonic boom
Hammer
Key (engineering)
Heat exchanger
Twoway radio
Gas
Diffraction
Sonar
Chandrasekhar limit
Kopfstütze
Metre
Audio frequency
Angle of attack
Interference (wave propagation)
Interstellar medium
Stromschlag
Caliber
32:15
Lugger
Sound
DopplerVerschiebung
Sonic boom
Harmonic
Optical amplifier
Particle physics
Cosmic distance ladder
Fieldeffect transistor
Wavelength
Be star
String theory
Atmosphere of Earth
Speed of sound
Shock wave
Material
Water vapor
Fundamental frequency
Speckle imaging
Sound pressure
Intensity (physics)
Pitch (music)
Source (album)
Scabies
Echo <Ballonsatellit>
Metre
Density
Audio frequency
Direct current
Cartridge (firearms)
Fahrgeschwindigkeit
Electronic media
Caliber
Bleisatz
Last
Microwave
00:05
Delay may remember be phenomenon of interference of believes in general and like any other way of on rates are also in the field for example if have to loudspeakers
00:20
Separated Some distance D They are produced Arab regimes that are in place Then depending on Where you received the sound of this You will observe Constructive Destructive partially destructive interference For example a point the distance between loudspeaker B and loudspeaker is the same and therefore both ways will constructively fear produce signal however if you some other position for example On Monday the distances different if I look at the triangle between loudspeaker 8 . 15 points And Mark off the short distance along the line of And count harmony wavelengths Is the the difference in halflength between loudspeaker a and loudspeakers beat them if this difference is that Brister being made Yeah equals A awful wavelength roughly half of wavelength fired of the wavelength Or so and so on them Destructive interference with however If it's an integral multiple ways length Our constructed and so let me a demonstrated the mother of a professor cast program so here we have votes to loudspeakers Who would the red and now we stocks The song from both of them and it shows Some positions And what you see in this little rectangle the oscillations of the functional Time due to wave 8 Redlon or the rule of law and the sound and you can see that in this case we have constructive interference because some the is roughly twice as speed The red and blue however that if I moved to a different place Would stumbled Although he then we have our almost complete destructive interference currency that The red and the rule out of faced with each other and therefore the sum is all about It is almost exactly equal to Vero can also change separation between the loudspeakers and then the distances between constructive interference and a destructive interference small so we get we get more zones off Constructive and said destructive interference in it The closer together All we can change the order the frequency And then we get even more of War zones a constructive and destructive interference next to each other so let's Calculate an example assume we have at the food loudspeakers on 1 leader of heart and a person stands for meters away from 1 of the world's questionnaires how far away from the others speaker does have to be to detect destructive interference when the loudspeakers image 1150 So the 1st problem we we have is to determine the wavelength and we know that The wavelength as the way velocity divided by the frequency and wave velocity years ago as the sun velocity of 343 meters per 2nd Find they divide that By Eddie 1150 Croats 1150 section of the frequency and we get the label and 0 . 1 Iron 8 All roughly a 3rd descended so that means J. year destructive interference A difference in distance must be equal to topple wavelength We half of all time out of blanks and so on and that means that Now we have several possible distances of for example weekend had 15 centimeters less of 15 sending more the 4 meters for 3 . 8 5 meters About 4 . 1 5 meters or we can have 45 centimeters more or less than the full of shit 3 . 5 5 meter or 4 . 4 What All we can 75 centimeters more or less than the form and that's the 3 . 2 5 4 . 7 5 the next set a witch Which would be a roughly 1 meter and 5 sending the different that cannot occur anymore because loudspeakers I only have 1 liter of solid fuel 4 meters away from 1 of the loudspeakers you can't be vast fund or 4 meters away from her from the other 2 . 9 6 meter away from the other that we now talk about different Type of interference interference that we discussed so far have basically happens in space look good positions in space and about Constructive destructive but if you have 2 waves off slightly Differing frequent better now and you look at a fixed position and space that you will get Constructive destructive interference at different points in time different instances In time as usual with interference Some the waves Have those waste which have slightly different frequencies And at 1 particular point we know that these equation of motion or Chris This given by a simple harmonic motion with the frequency of the 1st wave of this case and 2nd In that case this is the amplitude of both ways which used to be the same and the use this formula of power from trigonometry somewhat sign X Signed life But it was twice the size of the an of the average of X and Y times the cosine of onehalf of the difference and if you apply that this summer when we get twice the amplitude times Uh cosine of the difference divided by 2 times the time multiplied with the sign of the average frequency time terms time And we can consider this as a time dependent tool that this will be relatively slowly were compared with its soul and look at this summer which is indicated he waste a new pink and you get this red somewhere and became that define and act And envelope purchase this 1st part of The result Also timedependent but there is much more slowly and This is how envelope will look like 1 more of a professor at the demonstration approach
08:47
So 1st let's Just look at the 2 waves and let's not to own them slightly frequency both traveling in the same direction and if that if I allow them to interfere in 9 get be gleaned some of the frequency And we can now Look At the envelope as as a functional Time Andy Can try what happens if we d A frequencies and we see that the envelopes are still very fast just fast and eventually it had this kind of difficult to see it as an envelope with on Show Streak So what This kind of phenomenon is that usually referred to as As sole frequency 8 is a leading against frequency beat let's illustrate that this with example well let's say they have a tuning fork an average produces a steady 400 and This tuning fork struck And then held near vibrating guitar strings and If It should do about them and you can hear a distinct B and If you count them and you find out that there are indeed beats for every part And the question is what I'll be possible frequencies produced by And the answer is to beat frequency 20 needs divided by 5 seconds or that's about 4 roads and the beat frequency As shown on previously on the beach freed frequency is that is related to the difference of individual frequency and therefore the difference between the tuning fork Endicott calf strain passed before reports or it is that you don't put possibilities You have 396 of 404 so 1 can and make use of these 8 frequencies June Instruments were precise that's not all out Talk about Another complex phenomenon that Christopher sound waves but also for any other kind of way and it's called a The Doppler effect the observation is as follows a fuel and have a fire truck driving by the siren going then as it approaches to hear a higher pitch bend and when it passes you and when it goes away from you this phenomenon is called the Doppler effect effect and brokers You be sound source or the listener or the medium is ruled in the case of Flight of Doppler effect exists also by the only emotion that well over a source 2 At least if the largest moving back if the look Sources moving toward the listener um frequencies increased and the sources Moving away from the frequencies that 1st sconces just a moving source So on the case of a moving source Let's 1st consider the source not for resources and not knowing it admits Crests and Rincon can't goes and we can determine the wavelength for example The distance he is that supposed to be 1 labor If you compare that situation that the sources we we would observe a slightly different way because by the time we hear this crest The source has moved a little bit and renewed Now measure the distance from the next press it's somewhat closer than it was before and it is close by the speed of the tying the ties between 2 Crest switches period of For now the world's rely the wavelength appears to be sure About distance be source times a period of great since we email address time period is inversely related to the frequency and the That to be frequency times wavelength equal sounds that doesn't change sold at time period is 1 of the frequency And Divided Bars songs we can
13:57
Maria solemn speed A frequency Time wavelength which is 1 of the period Times Thinks so it multiplied by a teacher or will beat them to get TV also lumber over reader of Now
14:31
Add this expression at end of this expression and time period In this formula we get that amount of prying the changed wavelength is not minus a land and resource velocity divided by the And you can quote me labeling Slumdog expression of that Lambert prime equal slammed the times 1 minus She source of However we also know that We have the frequency that is associated with the hourly length Must be the sound speed divided by wavelength of substitute this winter That way she wouldn't be get that These changed frequency Prime equals about on speed divided by Expression frequency Prime equals the frequency divided by the fact the oneliners A source of a and indeed If Therefore primaries They don't Since the the denominator Eckert smaller than more you increase similarly Derive on expression and we are moving away from the And in that case at Lambeau primed longer abide by this amount So Basically replaces minus sign which comes from that minus signed by a plus sign And so in that Prime equals at 4 1 plus in that Case and a This frequencies And the denominator get bigger So Unfortunately professor cast but doesn't have a program for this Case but I've found 1 on the Web so if a tire pressure has led an improbable victory despite cage and runs this job the way we can have played with the Doppler effect as far part of moving resources so right now the source is moving at all so Brandeis as circulates going in all directions but the can now start will move the source
17:15
With higher and higher velocity and now you see that And wavelength in the direction of motion becomes a smaller part of the wave away from the direction of motion and perpendicular It the direction of motion and it is about the same I want it for Look And so it is now imagine standing here in this being the fire from of bigger frequency Pressed for a 2nd then as the truck process to buy you hear this The normal frequency of sirens and ran out the year truck Passed through The year frequency and walk across a few oppressed so the next question and we ask ourselves is what happens is not the sources moving but listen so let's say dealers sitting in a car on yourself and your listening to Osama from sounded stationed there what happens in that case what happens in that
18:28
Cases that the wavelength of the same because sources will but media the apparent some pilosity Increased if you moving toward the source of the The pool velocities add so we changed a song velocity Prime Minister some more normal songs plus the emotional list And that If you try wrapped in Chualar you expression relating frequency wavering then they get that these had changed frequency It's a times 1 plus The velocity Listen over the last and in this Place Uh at Prime is also bigger than because novice Expressionist and no more and normal rate getting bigger and bigger And I assume only if we move away from the source The year to varsity track and we get this expression These Who expressions are different than what we got from the EU moving source even if you change the sign of the velocity what we have here is that It matters The EU moved toward us soloists or other source is moving toward you always moving away from the Moving away from you So in other words This is manifestly and nonrelativistic Effect meaning that it doesn't just a matter of what the relative velocity of you with respect to source But it also matters how fast moving again Media which in this case the So what happens if we both the stores and listen And become combined have both fallen all 4 formed into 1 of the changed frequencies at times 1 plus or minus a listener sound Divided by 1 minus 0 plus a source in the last 4 for the listener means that the listener moves toward the source the minors for a listener that way and for this source That just means that the 1st move toward the Minus move away from you basically just have to remove this 1 formula can keep those I Signs straight So was There's a 3rd option and
21:26
Is Neither of us modest The ruling the medium has so far we have always consider that Is still virtually which transports the sound if there's some last somewhere in there and that there's also a Doppler effect and weekend You will need a principle of relativity issue the that's physics must be ruined rebellion over absolute motion not and so we can replace the ruling medium with a moving source of will list for example let's say their source and listen still but there's a
22:13
Some of the varsity been win that's going to what's the this weekend place that's an area with 1 member of the listener approached the source of the same velocity and the is moving away from him but that's in the past can use The previous form that cut it show that with examples of The Doppler effect so the 1st problem is reviewed the siren of a police car addressed And admits a rare predominant frequency of 1600 the question is what frequency will will you here if you are addressed and the police Car moves at a 25 meters per 2nd toward Suu or away from 48 part assumed that is moving toward Suu this case began removing source and Soweto prime equals Divided by 1 minus A source of a song leader Source with oddities Our leaders of the song velocities beyond what we need us for 2nd and regarded the numberless these frequency If the the police cars moving away from us and have minus sign gets replaced by last time and replied in the number of Bendigo 1490 that's now consider more complicated case let's say we have a stationary source of 5 thousand votes and the sound waves reflects from 1 object which moves with 3 . 5 meters The 2nd Toward the question is what is the frequency of The wave that is reflected by the moving object as Detected by detector address sort so what happens if you with a hammer Stationary source that emits a wave and as reflection on that interfaces that is kind of like this The object of this This Moving and then it emits the same frequency the listeners back again but that this will be detector moving stores so I read 1st calculated what is Frequency that object proceed better frequencies Prime equals at times 1 plus we listen all of these songs will be listeners The speed of the object So we applied in this on 5 meters per 2nd get 3 . 5 meters per 2nd Over 340 meters per 2nd and the 5 thousand exchanges of fire was 50 So are Now the frequency that is then Emitted by the object and not moving them listen for detected the rest of the source is then at this frequency divided by 1 plus also will be sound resources again the fire and in this case at Sources moving toward us until we get a minus sign so that if we do that then that the 5 thousand 50 changes to 5 thousand 100 So what means summary instead of 5 of reflection which Would have gotten from a stationary object you get 5 . 1 kilohertz reflection so if We have a frequency dependent detector we can actually measure the speed of the object and this is exactly how a radar gun works for police only that In this case a radio waves rather than sounds can also use this technique with sound to detect things like blood flows or not And if you so let's take it Doppler effect to an extreme let's go back To all moving soloists But let's increases speed by not in fact so much so that the speed of We are the objects is faster than the speed of the song And what happens in that case The past Eddie object process should open its own and sound Wave crests should have produced And then there there's is no more sound in front of the object of a sound as key object
27:12
And There is A constructive interference of a lot of ways press just this at the boundaries of what goes all the way out of the compound constructive and that means that right there it's allowed this is our usually error would refer a sonic boom so we calculate that the area the object is addressed to get circular Ashley crisis surrounding it wavelength doesn't change in any of the directions based on bullying and way get shorter and shorter in the direction of motion if at the sound speed and all be away from me just in front of the object and we go past that speed and there is a conical region sound the and Since this constructive interference of all those with protests here However high intensity just at this and there's also called a shark So and this comes about because song can't keep up with the emotional the the object we can actually socalled Mach number after the physicist much of which is B a ratio of The object be divided by the songs A plane will win with Mark No. 2 meters twice as fast And this much numbers related to The opening angle of the home opening angle means half the angle of the conical shape and sign of This opening angle be object or sound and therefore it It should be a sample of the object and therefore services Related inversely related the mark typical example All of such A supersonic booms Is it The crack of gunshot that's not to be confused Explosive really sort of gasses from from the gun which you can watch a shield of dampened with but the actual shot sulfur was snapped or crack and vectors Such a shock Produced by supersonic with a more familiar example perhaps supersonic jet fighter In this case as multiple shock waves basically every part of the plane Producing such a shock wave and in this Picture The shock waves are made visible and you see for example the shock wave of knows he has also won produced here and in general can distinguish those that are produced by the front of the plane and blow with up in detail but the reality is more complicated than just to shop or we can look at what awaits and a speed boat And then there are the same phenomenon happens the speed voted for it goes faster passes all of it Crest of its own weight and And that produces a shock wave that sort of wolves in somewhat comical shaved away from in the case of the jet Elaine Panasonic will not be a shock waves and worry intends can cause considerable damage for for example it can win Let me finish today of the various applications of found the first one that comes to mind are must detect underwater objects by using the time delay often echoing song in the sonar you a amid solemn pulse and then you wait for the reflection coming back 2 and a judge from the reflection of what kind of objects on you Or out tentatively with the same principle 1 appropriate Connell structural growth and using Braves traveling tho would be often these swathe of produced intentionally The explosion but I can also use earthquake waves that happened and naturally To maximize and the case of sold last 1 usually uses ultrasound waves and Bettis Because of a Wavelength shorter and therefore we Diffraction effects plus more It's a kind of was also used in medical imaging socalled sonogram images used for for diagnostic purposes and so it uses the the same principle as the St. Paul's echo technique so now typically frequencies used up between 1 and 10 megahertz
32:40
And echoes are observed from any kind of boundary in the body will be density changes for sample of organs Lesions or Cuomo's through fluid pockets or anything else In that case you have friends friends to so Place outside human and then married produces sounded reflects all of those areas Ingredients that you have in the human body and for each 1 of them receive an echo then that you repeat this procedure by replacing the funds to set of slightly different positions like this
33:21
Picture here and so if you make many such places to you observe different kind of Eccles and you can form a kind of image of what has happened Aside from Blair but you need to know of causes the the sound velocity body which Roughly the same as that of water or 1540 meters at the time delay between admitting the pulse and observing that related to distance The boundary twice the last Time and be intensity of The echo tells us something about the difference in density of the various media The most famous example probably will look Pictures A human or human fetus for example of 1 and 1 can see that it's possible to make a detailed picture and we can then make use of the Doppler effect to check whether that's a hot lead off our its used in them for other diagnostic purposes could detect The emotional bloodstream So let me know summarized Chapter 16 so 1st of all sound means But with Sensational consciousness about Physical phenomena that originates that has sound lays on along botulinal waves which means that air molecules for example vibrate Along the Directions propagation Saunders transported in a or other materials The sensation of pitch Is related to the frequency human beings can heal frequencies Between tainted goods and a 20 thousand The sensation of loudness is related to the intensity and the way we perceive loudness is proportional the Barber with intensity or I read can define the sound level has 10 dB times The Barber of all the intensity I divided by The intensity I'm not I'm not is taken As the human hearing special What 10 to the minus 12 walks the square The sources of sound of vibrating objects and typically standing waves of the Jews and those by ripping on a frequency All of the solemn in a L and is the same as the frequency of the vibrating object but the wavelength is typically different if the vibrating object is a string off some length or if it's an open air column in the tube that is open on both sides that the fundamental a wavelength the fundamental mode is given by twice the length and then odd and even higher harmonics exist and foreclosed to which means that 1 end disclosed the other 1 is open the fundamental wavelength its 4 times length and only odd harmonics Exerts a wave length off the end harmonica Given by a fundamental wavelength divided by And the frequency Given by fundamental frequency multiply and finally ended Doppler effect changes picture of sound or the frequency If the source or other listeners are moving using this formula is media moves 1 can replace that motion with the appropriate motion source and list objects moving faster than the on velocity Amid shock waves called sonic booms and saunas and medical in Ching devices use ultrasound echoes to determine that distances to objects
37:29
Thank you very much