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Gravitation and Maxwell's Electrodynamics, BOUNDARY CONDITIONS
Dear Sergey Karavashkin:
"Sergey Karavashkin" wrote in message om... Oh, you don't appreciate good attitude, David. I have read attentively your last post. You said many different things on me, but this is to your account. As I see, you put the question rigidly, requiring from me the photoeffect with wave physics. However, you didn't understand, I can explain it only to one who has a necessary amount of knowledge. Unfortunately, you still don't demonstrate such knowledge. There are lots of folks here that *do* have the wherewithal to hear all that you say. Try explaining it, as you suggest. Yes, I can explain photoeffect with the help of resonance phenomena in EM wave interaction with the electrons of substance. In metal they are the electrons of Fermi-gas, in semiconductors and dielectrics - orbital electrons. I briefly said you of it before. If you want to hear more, I'm pleased. But before I would like to make certain that you know resonance systems enough. Aren't you against? You wrote, Lets have it. [David] I took a class in "resonance systems". That is why I know that you have not even looked at what resonance is. I CAN calculate certain limited sets of exact solutions as the need arises. [Sergey] Okay. Since you put the question point-blank and state that you know in resonance systems what I don't, and also I know some resonant systems. I say you describe behaviours that are counter to my knowledge and experience. Enlighten the group. [David] There is no difficulty in expressing the formulas for resonance. And the behaviour is well known in lots of different types of systems. [Sergey] I will not bother you with complicated systems. Please go to page 42 of our paper "OSCILLATION PATTERN FEATURES IN MISMATCHED FINITE ELECTRIC LADDER FILTERS" http://angelfire.lycos.com/la3/selft...42/load42.html Circuit resonances. Has absolutely nothing to do with the photoelectric effect. .... and see formulas (23) - (25). This is the exact analytical solution for a heterogeneous line shown in Fig. 4a in the same page. You can make sure, these solutions are exact. It is sufficient for it to compare the diagrams in Fig. 6, page 44 http://angelfire.lycos.com/la3/selft...44/load44.html plotted with these formulas, with the experimental diagrams in Fig. 10, page 46 circuit resonance. Has absolutely nothing to do with the photoelectric effect. http://angelfire.lycos.com/la3/selft...46/load46.html The calculation of this mechanical elastic line is surely simple, takes several pages and a trifle of time. Please do show me, how I made it. This will make me sure that when I begin telling you, I will not see glassy eyes. ;-) No glassy eyes required to see the magician is trying misdirection again. After this we can advance into wave physics with a great speed, and you will soon see, wave physics is not so simple as you used to think outwardly, and photoeffect doesn't limit its scope. Sergey. P.S. I didn't want to touch other issues in this post, but couldn't resist a temptation. ;-) 1. In your post you stated unambiguously that photon has a "zero" size: [David] The size of the photon (as determined by experiment) is "zero", and has nothing to do with the distance it travels before it achieves the same E&B orientation again. At odd moment, could you explain me: if it has such size as you are saying, it must be smaller than a period of wave (at least for radio waves). It moves with the light velocity - it means, with the same velocity as vector E varies in space. Hence, I have natural questions: As I have said both to you and to Alexsandr, the concept of width is very fuzzy. Width in one sense has to do with establishing how far away something has to be to have zero effect on a particle "path". Width in a more conventional sense has to do with establishing how far from a path something has to be to have a definite measurable effect. I see only English has such duality of definition. a) the integral field of photon will be in this case non-zero, and what about uncharged photon? What integral and what field? The photon has no charge, correct. b) no changes in time can occur within photon, as with it the field variation registered by the receiver would be more either less than the light velocity (so-called group velocity which is formed when within some system there exists a subsystem with the time-variable phase shift); then of what changes of E&B are you saying? Why do you say time does not pass for the photon? It is not massive. Lorentz transforms do not apply to the c frame. Time does obviously seem to pass for the photon. c) If the wave period consists of multitude photons, how photons do correlate with each other, keeping a strong sequence for many thousands and millions kilometres, especially when there propagates not a monochromatic wave but a packet? "Period" is as descriptive for single photons, as it is for a host of similar photons. 2. As to the beyond-cutoff luminescence of substance you have written the following: [David] Or systems that express temperature, which is relative motion of the individual emitters and absorbers. This is simply saying that quantum mechanics is right. What is not right about what you have said is that it has anything to do with resonant behaviour. Absorption of a photon does *not* occur for electrons in orbitals that are just under a photon energy, and produce a near-zero KE electron, they produce a conduction electron with all the energy. This is NOT resonant behaviour. a) please show me the regularity of energy of secondary quanta in Planck formula with respect to temperature; ;-) *Which* Planck formula? I find many attributable to him. b) of which relative motion of individual emitters and absorbers are you saying for a solid state of luminophor which so much distorts the pattern of emission? Only having answered these questions, you may judge, how much right is QM. QM is not the issue. Your claim that wave theory describes the photoelectric effect is. 3. As to your following claim: [David] There are no behaviours that wave theory describes, that particle theory cannot. I guess, you are speaking here of the photon theory as a part of particle theory. If so, I would like simply to cite Niels Bohr: In the view of quantum theory, the discussed hypothesis cannot be nonetheless considered as a satisfying solution. As is known, just this hypothesis brings insurmountable difficulties in explanation of interference phenomena - the main means in studying the radiation properties [see: H.A. Lorentz. Phys. Zs., 1910, *11*, 349]. In any case we can ascertain that the underlying statement of the hypothesis of light quanta basically excludes the possibility to comprehend the concept of frequency nu playing the main part in this theory. So the hypothesis of light quanta is invalid to give general pattern of processes which might include the entire amount of phenomena considered in quantum theory applications [Niels Bohr. On the quantum theory application to the structure of atom. 1. The main postulates of quantum theory. Chapter 3. On formal nature of quantum theory. Item 1. Hypothesis of light quanta]. This organically supplements what I usually say you and you stubbornly don't hear. We all can take offence, the more when have such necessity to avoid answering inconvenient questions. This, David, is too trivial. ;-) Trivial and "satisfying". And can be said for any particle. So wave theory must extend to particles of all sorts. Are you up to that as well as describing the photoelectric effect? Of course you were were referring to QM, and not waves... 4. And one premature note on your dear photoeffect and your statement that [David] Wave theory does not describe the photoelectric effect, and particle theory does. [Sergey] Please take any book on photoeffect and open where the spectral characteristics for metals are shown. You will see that the quantum output dependence on frequency is not so much like a direct line as Planck equation predicts. These curves are gently sloping near the 'red' boundary and increasing as the square of difference of frequencies. After it you see an abrupt rise. And this rise relates to the frequency band at which the material stops effectively reflecting EM waves. The further the more. The curve reaches its maximum, then the photoeffect abruptly falls. Began the material again reflecting EM waves? Yes, but not so much abruptly as the quantum output falls. Well, now please answer, David, my very simple question. As a result of what there appears the maximum of absorption of EM waves by the surface of metal? And is completely beside the point for the photoelectric effect, since the "work function" describes the threshold, and "resonance" fails to describe the rest of the behaviour. In semiconductors the quantum output has some other pattern. In the area of red boundary you see an abrupt raise and saturation and almost smooth plateau. Here also the surface absorbs in the area of plateau? ;-) Of course, these are far from all questions, but if you can answer specifically at least to these - I will be grateful. ;-) Again, you have little regard fro what I have written to you in all earnestness. Like a good con man, you flash little lights, and wave your hands in other places to disguise the fact you would change the topic of discussion. The topic is "boundary conditions" for photons-as-waves, and you are not even close to describing them. David A. Smith |
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Gravitation and Maxwell's Electrodynamics, BOUNDARY CONDITIONS
Dear Aleksandr Timofeev:
"Aleksandr Timofeev" wrote in message om... \(formerly\)" dlzc1.cox@net wrote in message news:MaA_a.10404$2g.5230@fed1read05... .... Now you and Sergey have to describe the photoelectric effect using a wave model. Either use resonance, or come up with some other mechanism. Please David, give universal generalized physical definition of a resonance, which one is valid for linear and nonlinear physical systems simultaneously. Resonance is the arrival of momentum in a structure or node that has a similar direction to both the motion of the structure or node, the acceleration of the structure or node, and is "in-phase" with it. Rough, but perhaps close enough... Remember that resonance already has a definition, and a better one than mine. It defines a mechanism, and a behaviour, that is contrary to your needs. David A. Smith |
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Gravitation and Maxwell's Electrodynamics, BOUNDARY CONDITIONS
"George Dishman" wrote in message ...
"sean" wrote in message om... "George Dishman" wrote in message ... "sean" wrote in message om... ... Refarding the resonance point I just did a google search on `resonance` and the few things I found were all describing resonace as a function of waves overlapping. thats why I couldnt understand dlzs claim that resonance couldnt be described as waves I happened to come across this recently, it might help: http://colos1.fri.uni-lj.si/~colos/C...resonance.html Read what I could without going into the details of the equations .It still seems that david is wrong about resonace not being a wave phenomena? as this url also explains resonance in terms of amplitude, frequency, harmonics etc. All wave compatible descriptions While the two concepts are related, they are not the same. Resonance is a term that relates to a fixed system such as a pendulum, mass and spring, etc as listed on the web page. It refers to a system that has a natural mode of oscillation that can store energy in one place. When people talk about waves, they usually mean something with a repetitive characteristic that also moves. Waves can carry energy from one place to another. Consider an example of a weighted buoy on the sea. In flat calm water, if you hit the buoy, it will bob up and down at some rate. The energy you gave it in the initial impact is stored as a combination of kinetic and potential energy and is slowly lost to heat in the water. If waves hit the buoy at that same rate as it bobs, then they can give it more energy than it loses in each cycle so the amplitude will increase. At any other rate the waves may at first add energy but as they get out of phase they tend to remove it. So David is right, a pendulum for example is a resonant system but it is not a 'wave phenomenon'. To put it crudely, waves travel, pendulums don't. The equation for the swing is: y(t) = a * sin(w*t + p) where a is the amplitude, w is the angular frequency, t is time and p is the initial phase. For a wave it is: y(x,t) = a * sin(w*(t-x/v) + p) where v is the speed of the wave and x is a distance. George Hi George Yes I can understand that an object can have or generate `resonance` but it is true also to say that standing waves and vibrating nodes in mediums like sand water etc also can be said to be resonant systems and store energy and be measured in the same terms of frequencies oscillations as objects. These phenomena are also essentially identical to what would be termed a wave only atom or `particle` . They are stationary and point like but are not objects like pendulums or particles but superimpositions of many waves on a point source.So it seems to me that for david to say only particles can explain resonance is incorrect and wave only models seen classically as standing wave s are also resonant systems Sean |
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Gravitation and Maxwell's Electrodynamics, BOUNDARY CONDITIONS
\(formerly\)" dlzc1.cox@net wrote in message news:mLR4b.42838$Qy4.37371@fed1read05...
Dear Aleksandr Timofeev: "Aleksandr Timofeev" wrote in message om... \(formerly\)" dlzc1.cox@net wrote in message news:MaA_a.10404$2g.5230@fed1read05... ... Now you and Sergey have to describe the photoelectric effect using a wave model. Either use resonance, or come up with some other mechanism. Please David, give universal generalized physical definition of a resonance, which one is valid for linear and nonlinear physical systems simultaneously. Resonance is the arrival of momentum in a structure or node that has a similar direction to both the motion of the structure or node, the acceleration of the structure or node, and is "in-phase" with it. Rough, but perhaps close enough... In other words, you state, that the physical phenomenon of a resonance in "structure" has a place under following conditions: - the orientation of "structure" should be strictly coordinated with orientation of electromagnetic radiation (one of a series of requirements of co-ordinating); - the FREQUENCY of absorbed radiation should be such, what the COMPLETE RESISTANCE of system has become a pure RESISTANCE; - by the way, you have forgotten about co-ordinating impedances of "structure" and medium of propagation of electromagnetic radiation, i.e. about efficiency of the transformer of radiation! ("structure"); I should mark a very large virtue of your DEFINITION of a RESONANCE, in which one the concrete physical MECHANISM of ABSORPTION of EXTERIOR electromagnetic radiation MISSES. Yours " structure " has other title a " BLACK BOX ". Remember that resonance already has a definition, and a better one than mine. We are agreed on this. ;-) I shall give more perfect definition of a resonance: It seems to me, that I have representation about a resonance with another of more generalized physical point of view. Let's consider PHYSICAL SYSTEM, which one ABSORBS EXTERIOR electromagnetic radiation, as a BLACK BOX. I.e. we abstract from the concrete physical mechanism of ABSORPTION of EXTERIOR electromagnetic radiation. Only FREQUENCY BANDS of MAXIMUM ABSORPTION of electromagnetic radiation have concern for us. These AREAS of frequencies of MAXIMUM ABSORPTION of electromagnetic radiation we shall term as AREAS of a RESONANCE of SYSTEM. From my point of view the given DEFINITION of a RESONANCE is most GENERALIZED physical DEFINITION of a PHENOMENON of a RESONANCE. In this definition of a RESONANCE is included EFFICIENCY of the COORDINATION of the system with MEDIUM (space), in which one the radiation is spread. It defines a mechanism, and a behaviour, that is contrary to your needs. Let's consider the problem closer. Our positions are much closer than you guessed earlier. Our positions coincide everywhere except for final deductions. To err is human. I am sure, that you err. Please look above: " AREAS of frequencies of MAXIMUM ABSORPTION " Aleksandr Timofeev |
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Gravitation and Maxwell's Electrodynamics, BOUNDARY CONDITIONS
Dear Aleksandr Timofeev:
"Aleksandr Timofeev" wrote in message om... \(formerly\)" dlzc1.cox@net wrote in message news:mLR4b.42838$Qy4.37371@fed1read05... .... Please David, give universal generalized physical definition of a resonance, which one is valid for linear and nonlinear physical systems simultaneously. Resonance is the arrival of momentum in a structure or node that has a similar direction to both the motion of the structure or node, the acceleration of the structure or node, and is "in-phase" with it. Rough, but perhaps close enough... In other words, you state, that the physical phenomenon of a resonance in "structure" has a place under following conditions: - the orientation of "structure" should be strictly coordinated with orientation of electromagnetic radiation (one of a series of requirements of co-ordinating); Orientation only of the velocity and acceleration vectors at the "instant" of momentum transference. - the FREQUENCY of absorbed radiation should be such, what the COMPLETE RESISTANCE of system has become a pure RESISTANCE; Mostly correct. Only linear systems (and simple systems at that) will there be no other "harmonics" or energy trasnferred to, and stored/lost from other portions of a structure. - by the way, you have forgotten about co-ordinating impedances of "structure" and medium of propagation of electromagnetic radiation, i.e. about efficiency of the transformer of radiation! ("structure"); I did not forget. Your synopsis (assuming I was an idiot and only looked in the book for five minutes) assumed so. I should mark a very large virtue of your DEFINITION of a RESONANCE, in which one the concrete physical MECHANISM of ABSORPTION of EXTERIOR electromagnetic radiation MISSES. Yours " structure " has other title a " BLACK BOX ". As its definition intends. I am not trying to paint you into a corner with words. I expect the facts will do this to you shortly. Remember that resonance already has a definition, and a better one than mine. We are agreed on this. ;-) I shall give more perfect definition of a resonance: It seems to me, that I have representation about a resonance with another of more generalized physical point of view. Let's consider PHYSICAL SYSTEM, which one ABSORBS EXTERIOR electromagnetic radiation, as a BLACK BOX. Accepted. Just as a particle is not to be located in space, based on its definition. I.e. we abstract from the concrete physical mechanism of ABSORPTION of EXTERIOR electromagnetic radiation. Only FREQUENCY BANDS of MAXIMUM ABSORPTION of electromagnetic radiation have concern for us. These AREAS of frequencies of MAXIMUM ABSORPTION of electromagnetic radiation we shall term as AREAS of a RESONANCE of SYSTEM. Henceforth known as 'ARS'. The photoelectric effect shows none. Only a threshold. From my point of view the given DEFINITION of a RESONANCE is most GENERALIZED physical DEFINITION of a PHENOMENON of a RESONANCE. In this definition of a RESONANCE is included EFFICIENCY of the COORDINATION of the system with MEDIUM (space), in which one the radiation is spread. Accepted. The photoelectric effect shows no ARS. Only a threshold. DOA. It defines a mechanism, and a behaviour, that is contrary to your needs. Let's consider the problem closer. Our positions are much closer than you guessed earlier. Our positions coincide everywhere except for final deductions. To err is human. I am sure, that you err. Please look above: " AREAS of frequencies of MAXIMUM ABSORPTION " I have not erred. I have provided rope and you have made your own trap. You of course have caught only yourself. David A. Smith |
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Gravitation and Maxwell's Electrodynamics, BOUNDARY CONDITIONS
"Aleksandr Timofeev" wrote in message om... "George Dishman" wrote in message ... "Aleksandr Timofeev" wrote in message om... Dear George: Look at Subject: "Gravitation and Maxwell's Electrodynamics, BOUNDARY CONDITIONS" No Aleksandr, look at sean's original posts to which I was replying: (sean) wrote in message . com... Hi I have already given a mathematiucal description of how waves can produce the photoelectric effect but I am puzzled why you dont believe resonace cant. Isnt resonance always described as a wave function or as a overlapping of waves ? So the context was 'could resonance explain the photoelectric effect' regardless of the subject line. I'll leave that to Sean. "sean" wrote in message om... ... Refarding the resonance point I just did a google search on `resonance` and the few things I found were all describing resonace as a function of waves overlapping. thats why I couldnt understand dlzs claim that resonance couldnt be described as waves A standing wave pattern in a cavity can certainly be described as a resonant system, but that is not the only way to produce resonance. Without getting into esoteric QM considerations, you cannot descibe a pendulum as "a function of waves overlapping". It seems, that Sean has representation about a resonance with another of more generalized physical point of view. Sean views PHYSICAL SYSTEM, which one ABSORBS EXTERIOR electromagnetic radiation, as a BLACK BOX. Then there is no problem with the suggestion that the box forms a resonant systems if it can contain and accumulate energy from the incoming wave. (BTW, there is no need to shout.) I.e. Sean abstracts from the concrete physical mechanism of ABSORPTION of EXTERIOR electromagnetic radiation. Only FREQUENCY BANDS of MAXIMUM ABSORPTION of electromagnetic radiation have concern for Sean. Since he was talking of the photoelectric effect that seems less likely since one of the key results is that the energy of the emitted electrons is linearly related to the illuminating frequency. However, I would leave discussion of that to Sean. These AREAS of frequencies of MAXIMUM ABSORPTION of electromagnetic radiation Sean terms as AREAS of a RESONANCE of SYSTEM. Again, it would be quite reasonable to suggest that absorbtion bands could be caused by resonance, I have no argument with that if that is what he is saying. From my point of view the given DEFINITION of a RESONANCE is most GENERALIZED physical DEFINITION of a PHENOMENON of a RESONANCE. In this definition of a RESONANCE is included EFFICIENCY of the COORDINATION of the system with MEDIUM (space), in which one the radiation is spread. In my view the key feature is not efficiency of coupling but of storage as defined by the Q factor. I think that is a conventional classification. George |
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Gravitation and Maxwell's Electrodynamics, BOUNDARY CONDITIONS
In sci.astro George Dishman wrote:
The key difference is that in an LC circuit, energy can be stored in the magnetic field in the inductor and in the electric field in the capacitor. The collapse of the magnetic field induces a voltages that charges the capacitor, the voltage across the capacitor then builds the current in the inductor in the opposite sense to the original and so on. Without resistive losses this could go on indefinitely. With just an RC, the energy in the capacitor is turned into heat in the resistor and that is the end. of course the "R" in the RC isn't a requirement. The whole key to oscillations (resonance) is time. Any feedback system can become unstable and have oscillations if the timing is right. The key is to have a positive feedback situtation. It's just another way to describe a resonant system. The essence of the resonance has to do with shifts in time. Bjacoby -- SPAM-Guard! Remove .users (if present) to email me! |
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Gravitation and Maxwell's Electrodynamics, BOUNDARY CONDITIONS
"George Dishman" wrote in message ...
"sean" wrote in message om... Hi Sean, Take a very long taut wire and send two bursts of a wave of the same frequency travelling in opposite directions from the ends towards the cent --\/\/\/\/\/\/\----------------------/\/\/\/\/\/\/\/--- --- --- When they meet in the middle, they will create a standing wave pattern of while they overlap (it's twice the height but I can't show that) and pass through each other -----------------\/\/\/\/\/\/\------------------------ after that they just separate though --\/\/\/\/\/\/\----------------------/\/\/\/\/\/\/\/--- --- --- The interference pattern in the middle is a wave phenomenon but it is not resonance. Now put a clamp on the wire to stop it moving at each end of a section ------------------------------------------------------ ^ ^ If you tap one end of the wire, it will vibrate. If you tap in sync with the vibration, each tap adds a little energy and the amplitude builds up. This is a resonant system. The obvious example is a violin. Another form of a resonant system is something I have used for many years is where you touch a string lightly and pluck it at the same time . If the string is secured at both ends the string will vibrate at two different but related wavelengths like 1/2 or 1/3 2/3 and a `harmonic ` is produced. I use this method to tighten guitar strings accurately by tuning one string to the equivelent harmonic of another .. Or if you hum at a steady note into a instrument cavity like a guitar or violin or even piano at certain notes the cavity will resonate and amplify and sustain ones voice as the strings and cavity `resonate`. Similarly as you alluded to earlier if one places a tuning fork onto an instrument or near a loud enough pure note of same frequency or a harmonic of the tuning forks frequency it will begin to vibrate `sympathetically`. And check out the whispering gallery at St Pauls in London. That aural illusion is I would say a building`s interior `exhibiting` resonance. Now think of two mirrors, or a pice of wave guide with the ends closed off. You can inject light and get a laser or inject RF and get a standing wave as Aleksandr said. These are also resonant but they are called "resonant cavities" because it is the act of closing off the ends that creates the resonance. and store energy and be measured in the same terms of frequencies oscillations as objects. These phenomena are also essentially identical to what would be termed a wave only atom or `particle` . They are stationary and point like They are stationary but cannot be point-like because the length of the cavity must be an integer multiple of half the wavelength. but are not objects like pendulums or particles but superimpositions of many waves on a point source.So it seems to me that for david to say only particles can explain resonance is incorrect and wave only models seen classically as standing wave s are also resonant systems Superimposition and standing waves are not of themselves resonant. What creates the resonance is the cavity that contains them, it is the cavity that is described as resonant and the waves are merely the form of energy that it stores. You sound confused here and I think you are trying to somehow say that the medium within the container doesnt resonate and that therefore I am wrong and yet you have to admit that yes the medium does resonate because you know it does. Its a tricky situation you and David are in although I think you actually understand resonance and David doesnt. Take a vibrating plate of sand and watch the nodes scattered about surface . They are raised humps of sand each in static position and each hump or node is centerd about 1 point on the plate yet each node is not a distinct object with a distinct edge. Furthermore you can even manipulate these nodes and move them by touching the plate with your finger.These nodes ARE the equivelent of what I call wave only atoms in a medium. Furthermore these nodes are what you call the exhibition of resonance. Yet each node is not an object but a standing wave focused at a point like location in space. The medium in which these nodes appear is not one object but can consist of air, gas, water sand etc. It isnt then the cavity that resonates but the medium within the cavity that resonates What I find amusing is I can tell from your posts that you know that a constrained medium CAN resonate in the same way as a constrained object like a string can resonate. Yet you realize that by admitting this truism you have to admit that David is wrong in saying that only an object or single particle can resonate and the uncomfortable truth you face is to admit that a concept of a wave only atom as a point like node of superimposed waves in a medium like an aether has observable analogies in everyday life. Tell me George, is it the container only that resonates or is it the medium within the container and the container that resonates? Is it just the string that resonates? Is it just the string and the violin that resonate? Or is it the string, the violin AND the air within the body of the violin that resonates? If you say no to this last example then you are wrong as it is possible to muffle and completely change the resonance or sound of a stringed instrument by stuffing a rag into the interior of it to prevent the medium of air within the container from resonating. The string still resonates and the wood to a lesser degree but the air doesnt. And because the air doesnt resonate their are less sympathetic resonations in the wood casing of the instrument. If you ever get the opportunity, try this experiment with a stringed instrument. I have. In other words David is completely wrong in saying that a single particle or object vibrating is the only manifestation of resonance. Far from it . A medium can also resonate and within that medium observation tells us that there are nodal points where the amplitude is greater and these are comparable to...wave only atoms . Sean |
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Gravitation and Maxwell's Electrodynamics, BOUNDARY CONDITIONS
"sean" wrote in message om... "George Dishman" wrote in message ... "sean" wrote in message om... Hi Sean, Take a very long taut wire and send two bursts of a wave of the same frequency travelling in opposite directions from the ends towards the cent --\/\/\/\/\/\/\----------------------/\/\/\/\/\/\/\/--- --- --- When they meet in the middle, they will create a standing wave pattern of while they overlap (it's twice the height but I can't show that) and pass through each other -----------------\/\/\/\/\/\/\------------------------ after that they just separate though --\/\/\/\/\/\/\----------------------/\/\/\/\/\/\/\/--- --- --- The interference pattern in the middle is a wave phenomenon but it is not resonance. Now put a clamp on the wire to stop it moving at each end of a section ------------------------------------------------------ ^ ^ If you tap one end of the wire, it will vibrate. If you tap in sync with the vibration, each tap adds a little energy and the amplitude builds up. This is a resonant system. The obvious example is a violin. Another form of a resonant system is something I have used for many years is where you touch a string lightly and pluck it at the same time . If the string is secured at both ends the string will vibrate at two different but related wavelengths like 1/2 or 1/3 2/3 and a `harmonic ` is produced. I use this method to tighten guitar strings accurately by tuning one string to the equivelent harmonic of another . Or if you hum at a steady note into a instrument cavity like a guitar or violin or even piano at certain notes the cavity will resonate and amplify and sustain ones voice as the strings and cavity `resonate`. Similarly as you alluded to earlier if one places a tuning fork onto an instrument or near a loud enough pure note of same frequency or a harmonic of the tuning forks frequency it will begin to vibrate `sympathetically`. Right, all those are good examples. And check out the whispering gallery at St Pauls in London. That aural illusion is I would say a building`s interior `exhibiting` resonance. I'm not sure about that, I think it is more to do with focussing of the sound as it is reflected off the curved surfaces but I haven't been there so that is an uniformed opinion. Now think of two mirrors, or a pice of wave guide with the ends closed off. You can inject light and get a laser or inject RF and get a standing wave as Aleksandr said. These are also resonant but they are called "resonant cavities" because it is the act of closing off the ends that creates the resonance. and store energy and be measured in the same terms of frequencies oscillations as objects. These phenomena are also essentially identical to what would be termed a wave only atom or `particle` . They are stationary and point like They are stationary but cannot be point-like because the length of the cavity must be an integer multiple of half the wavelength. but are not objects like pendulums or particles but superimpositions of many waves on a point source.So it seems to me that for david to say only particles can explain resonance is incorrect and wave only models seen classically as standing wave s are also resonant systems Superimposition and standing waves are not of themselves resonant. What creates the resonance is the cavity that contains them, it is the cavity that is described as resonant and the waves are merely the form of energy that it stores. You sound confused here and I think you are trying to somehow say that the medium within the container doesnt resonate and that therefore I am wrong and yet you have to admit that yes the medium does resonate because you know it does. Resonance is a behaviour that is often associated with a system and the medium plays its part, but lets see... Its a tricky situation you and David are in although I think you actually understand resonance and David doesnt. Take a vibrating plate of sand and watch the nodes scattered about surface . Right, now this is a pattern produced by flexing of the plate or by interference of sound travelling through the plate and being reflected from the boundary. Clearly the medium is essential, no plate, no resonance. They are raised humps of sand each in static position and each hump or node is centerd about 1 point on the plate yet each node is not a distinct object with a distinct edge. Furthermore you can even manipulate these nodes and move them by touching the plate with your finger.These nodes ARE the equivelent of what I call wave only atoms in a medium. Furthermore these nodes are what you call the exhibition of resonance. No, that is the subtlety. You can get node by reflecting a moving wave of a mirror but that is not resonance, just two wave phenomena, reflection and interference. The single mirror doesn't store energy while your vibrating plate could. Yet each node is not an object but a standing wave focused at a point like location in space. Nodes are actually points where the waves cancel. That minor point aside, note that the nodes are produced by superposition of two waves that are moving in opposite directions. Without something to reflect them back and localise the energy, you just have two overlapping waves, not resonance. The medium in which these nodes appear is not one object but can consist of air, gas, water sand etc. It isnt then the cavity that resonates but the medium within the cavity that resonates No, it is the combination. That's why I emphasise it is a system not just the medium. For example your plate would not resonate if it were infinite in size, it is the boundaries that create the resonance. What I find amusing is I can tell from your posts that you know that a constrained medium CAN resonate in the same way as a constrained object like a string can resonate. Certainly. Yet you realize that by admitting this truism you have to admit that David is wrong in saying that only I haven't seen David's posts and I am no concerned who is right or wrong, I am trying to help by clarifying the terminology, not commenting on your ideas. an object or single particle can resonate and the uncomfortable truth you face is to admit that a concept of a wave only atom as a point like node of superimposed waves in a medium like an aether has observable analogies in everyday life. Sure, but just waves in a medium on their own would simply disperse. Tell me George, is it the container only that resonates or is it the medium within the container and the container that resonates? Is it just the string that resonates? Is it just the string and the violin that resonate? Or is it the string, the violin AND the air within the body of the violin that resonates? If you put the violin in a vacuum chamber, would the string still vibrate when bowed? Would an infinitely long string resonate when bowed in air or in a vacuum? (Hint - how would you calculate the note?) It takes the string _plus_ the bridge and a fret to create a resonance. The medium in all these cases is the string. In the violin, the vibration of the string is coupled to the body where there are further quite separate resonances in the panels as you described earlier. (See "Chladni patterns" he http://www.phys.unsw.edu.au/~jw/strings.html ) Those patterns move the air and that can excite a further resonance formed by the air inside the body. That is called a Helmholtz Resonance and is again defined by the cavity. Of course no air, no resonance in this case, but for the string, bridge and fret resonance, putting the violin in a vacuum chamber would actually increase the Q of the resonance since a large part of the power lost from the string goes into moving the air via the mechanical linkages to make the sound we hear. If you say no to this last example then you are wrong as it is possible to muffle and completely change the resonance or sound of a stringed instrument by stuffing a rag into the interior of it to prevent the medium of air within the container from resonating. It muffles it best if it doesn't prevent the motion but allows it while resisting it. The energy isn't reflected back then but gets turned into a tiny amount of heat in the rag through friction. The more power you can absorb, the more you damp the resonance. The string still resonates and the wood to a lesser degree but the air doesnt. You certainly eliminate the Helmholtz resonance but the others are still present though they are now damped. This reduces the Q in contrast to operation in a vacuum which increases the Q. And because the air doesnt resonate their are less sympathetic resonations in the wood casing of the instrument. If you ever get the opportunity, try this experiment with a stringed instrument. I have. In other words David is completely wrong in saying that a single particle or object vibrating is the only manifestation of resonance. If that is what he said, he is wrong (e.g. plantary orbital resonances). If you said you can get resonance with waves in a medium but nothing else then you are also wrong. Far from it . A medium can also resonate and within that medium observation tells us that there are nodal points where the amplitude is greater ... Nodes are locations of zero amplitude, antinodes are locations of maxima, but these can also be produced by interference without resonance. A pendulum is resonant with no waves involved. I am hoping you can see the distinction in the terminology. ... and these are comparable to...wave only atoms . Rather like the wave function used to describe particles in QM you mean? I have no argument with that but I would not call it a resonance, unless you are calculating an electron in a potential well ;-) George |
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