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#111
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On Jun 2, 2:12*pm, Cecil Moore wrote:
On Jun 2, 8:57*am, K1TTT wrote: wave function solutions to maxwell's equations are enough to prove that for me. Not a loaded question: How do Maxwell's equations applied to a standing wave prove that the component forward and reflected waves are moving at the speed of light in the medium? If it can and if I can understand it, I wouldn't need to use the photon argument. -- 73, Cecil, w5dxp.com easy, maxwell's equations don't predict standing waves! they are a product of superposition and the simplest instrumentation used since they were first discovered. |
#112
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On Jun 2, 9:31*am, K1TTT wrote:
easy, maxwell's equations don't predict standing waves! *they are a product of *superposition and the simplest instrumentation used since they were first discovered. Please correct me if I am wrong: If one starts with the (superposed) standing wave equation, V(x,t) = A*sin(kx)*sin(wt), Maxwell's equations seem to provide a perfectly valid result (not that I can recognize perfection). Therefore, how do Maxwell's equations prove that the component traveling waves necessarily possess a separate existence? Again, a serious question from an engineer who considers anything except a logical '0' or logical '1' to be broken. :-) -- 73, Cecil, w5dxp.com |
#113
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On Jun 2, 3:13*pm, Cecil Moore wrote:
On Jun 2, 9:31*am, K1TTT wrote: easy, maxwell's equations don't predict standing waves! *they are a product of *superposition and the simplest instrumentation used since they were first discovered. Please correct me if I am wrong: If one starts with the (superposed) standing wave equation, V(x,t) = A*sin(kx)*sin(wt), Maxwell's equations seem to provide a perfectly valid result (not that I can recognize perfection). Therefore, how do Maxwell's equations prove that the component traveling waves necessarily possess a separate existence? Again, a serious question from an engineer who considers anything except a logical '0' or logical '1' to be broken. :-) -- 73, Cecil, w5dxp.com my differential calculus is a bit rusty, but i don't think that equation satisfies the basic wave equation. from Fields and Waves in Communication Electronics, section 1.14. a solution for the wave equation in a transmission line (or other 1d form) must satisfy the condition that the 2nd derivative wrt x and wrt t equal v-squared... too hard to write in text. but basically take the above and differentiate twice wrt time and twice wrt distance and i don't think you'll get anything that comes out to the velocity squared. the problem is that t and x must be part of the same sinusoid in the F(t-x/ v) so that the wave is truly traveling instead of stationary like your equation provides. in the basic maxwell equations in differential form you also run into the same problem where the curl of the one field is proportional to the time derivative of the other i think you'll end up with a contradiction like k=w if you eliminate the dimensionless terms... i may be wrong on that because its been so long since i've had to deal with them on that level. |
#114
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On 2 jun, 13:48, K1TTT wrote:
On Jun 2, 3:13*pm, Cecil Moore wrote: On Jun 2, 9:31*am, K1TTT wrote: easy, maxwell's equations don't predict standing waves! *they are a product of *superposition and the simplest instrumentation used since they were first discovered. Please correct me if I am wrong: If one starts with the (superposed) standing wave equation, V(x,t) = A*sin(kx)*sin(wt), Maxwell's equations seem to provide a perfectly valid result (not that I can recognize perfection). Therefore, how do Maxwell's equations prove that the component traveling waves necessarily possess a separate existence? Again, a serious question from an engineer who considers anything except a logical '0' or logical '1' to be broken. :-) -- 73, Cecil, w5dxp.com my differential calculus is a bit rusty, but i don't think that equation satisfies the basic wave equation. *from Fields and Waves in Communication Electronics, section 1.14. *a solution for the wave equation in a transmission line (or other 1d form) must satisfy the condition that the 2nd derivative wrt x and wrt t equal v-squared... too hard to write in text. *but basically take the above and differentiate twice wrt time and twice wrt distance and i don't think you'll get anything that comes out to the velocity squared. *the problem is that t and x must be part of the same sinusoid in the F(t-x/ v) so that the wave is truly traveling instead of stationary like your equation provides. in the basic maxwell equations in differential form you also run into the same problem where the curl of the one field is proportional to the time derivative of the other i think you'll end up with a contradiction like k=w if you eliminate the dimensionless terms... i may be wrong on that because its been so long since i've had to deal with them on that level. Oh!, I surrender :) The thread do not converge to a solution, it seems run out toward a naked singularity! I stay tuned until this good brainstorm calms down .. Miguel |
#115
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On Jun 2, 5:56*pm, lu6etj wrote:
On 2 jun, 13:48, K1TTT wrote: On Jun 2, 3:13*pm, Cecil Moore wrote: On Jun 2, 9:31*am, K1TTT wrote: easy, maxwell's equations don't predict standing waves! *they are a product of *superposition and the simplest instrumentation used since they were first discovered. Please correct me if I am wrong: If one starts with the (superposed) standing wave equation, V(x,t) = A*sin(kx)*sin(wt), Maxwell's equations seem to provide a perfectly valid result (not that I can recognize perfection). Therefore, how do Maxwell's equations prove that the component traveling waves necessarily possess a separate existence? Again, a serious question from an engineer who considers anything except a logical '0' or logical '1' to be broken. :-) -- 73, Cecil, w5dxp.com my differential calculus is a bit rusty, but i don't think that equation satisfies the basic wave equation. *from Fields and Waves in Communication Electronics, section 1.14. *a solution for the wave equation in a transmission line (or other 1d form) must satisfy the condition that the 2nd derivative wrt x and wrt t equal v-squared... too hard to write in text. *but basically take the above and differentiate twice wrt time and twice wrt distance and i don't think you'll get anything that comes out to the velocity squared. *the problem is that t and x must be part of the same sinusoid in the F(t-x/ v) so that the wave is truly traveling instead of stationary like your equation provides. in the basic maxwell equations in differential form you also run into the same problem where the curl of the one field is proportional to the time derivative of the other i think you'll end up with a contradiction like k=w if you eliminate the dimensionless terms... i may be wrong on that because its been so long since i've had to deal with them on that level. Oh!, I surrender *:) The thread do not converge to a solution, it seems run out toward a naked singularity! *I stay tuned until this good brainstorm calms down .. Miguel it will never converge, these discussions always go on until the namecalling starts, then die an ugly death. |
#116
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On Jun 2, 8:00*am, Cecil Moore wrote:
On Jun 2, 5:33*am, Keith Dysart wrote: I suggest that you immediately dump any reference that includes a phrase like "photon energy present in a wave". If you (and others) will give up on the ridiculous concept of EM wave energy standing still in standing waves, I will not have to refer to photons again. Refering to photons is just fine. Just do not mix them in with wave theory. Honor the technical fact that EM forward waves (with an associated ExH energy) and EM reflected waves (with an associated ExH energy) are always present when standing waves are present and that those underlying waves (that cannot exist without energy) are moving at the speed of light in the medium back and forth between impedance discontinuities. Standing waves are somewhat of an illusion and according to two of my reference books, do not deserve to be called waves at all because standing waves do not transfer net energy as required by the definition of "wave". In short, it is impossible for EM waves to stand still. Quoting one of my college textbooks, "Electrical Communication", by Albert: "Such a plot of voltage is usually referred to as a *voltage standing wave* or as a *stationary wave*. Neither of these terms is particularly descriptive of the phenomenon. A plot of effective values of voltage, appearing as in Fig. 6(e), *is not a wave* in the usual sense. However, the term "standing wave" is in widespread use." From "College Physics", by Bueche and Hecht: "These ... patterns are called *standing waves*, as compared to the propagating waves considered above. They might better not be called waves at all, since they do not transport energy and momentum." All quite orthogonal to the original point, but your point about standing waves is quite correct, they are not really waves at all. But your need for the reality of underlying waves is quite excessive. The voltage and current distribution on a transmission line can be solved with a set of differential equations which satisfy some boundary conditions. There is no mention of forward and reverse waves in this solution. Turns out though, that the solution can also be factored in to a forward and reflected wave and this technique will provide the same answer. It does not make these waves any more real. I bring you back to a previous question which you have never answered... On an ideal line with 100% reflection, there are points where the current and voltage is always 0. Knowing that if either current or voltage is 0, power is also 0, how does energy cross these point? And if I cut the line at all the places where the current is zero, it does not alter the energy distribution on the line one iota. How can this be if energy is travelling from end to end on the line? Technically, RF waves *are* light waves, just not *visible* light waves. All the laws of physics that govern EM waves of light also apply to RF waves. PHYSICS has long given up on the idea of waves being an explanation for light. The wave theory fails miserably when illumination levels drop to the level that individual photons are being detected. Though of course the earlier approximate models (waves) are still useful when intensity is high enough, just as we still use Newtonian mechanics to solve many every-day problems. You might like to try http://vega.org.uk/video/subseries/8 for an exposition on the strangeness of photon. That you find it inconvenient for your "mashed- potatoes" theory of energy arguments is not a good reason to abandon the photonic nature of EM waves. There you go again... mixing up you models. EM waves are analog and in no way encompass the quantum nature of photons. It is actually a good reason to keep it in mind and abandon the mashed-potatoes energy arguments as human conceptual constructs that cannot exist in reality. Most of the energy in an EM wave is kinetic energy. Therefore, it cannot stand still. There seems to be some misapprehension here. No one has claimed that EM waves stand still, though you may have been confused by the word 'standing' in 'standing waves'. But then earlier in your post you quote 'College Physics' about 'standing waves', so it is not clear where your confusion originates. There is a wave theory of light, and there is a particle theory of light, and these two theories do not play well together. If they are both correct, they should play well together. If there is any conflict, quantum electrodynamics wins the argument every time. They are not both correct. QED aligns with many more observations than does the wave theory. Another reason not to mix them. While in many situations they will yield the same answers, it is not permissible to mix the concepts from each. Distrust the conclusions of any exposition which does so. Actually, distrust the wave theory if it disagrees with QED. Quantum ElectroDynamics has never been proven wrong. And the wave theory does disagree with QED at low levels, while at higher illumination levels QED agrees with the wave theory. So feel free to prove that standing waves can exist without the underlying component traveling waves traveling at the speed of light in the medium. Feel free to prove that EM wave cancellation does not "redistribute energy to areas that permit constructive interference" as the FSU web page explains. Feel free to prove the Melles-Groit web page wrong when they say such has been proven experimentally. In fact, the interferometer experiment described here proves that reflected EM waves, traveling at the speed of light, exist along with the necessary energy. Take a look at the "non-standard output to screen". And yet known of this aligns with the photons being part of the wave theory of light. They two theories remain distinct. http://www.teachspin.com/instruments...eriments.shtml I, personally, am not interested in getting the right answer using the wrong concepts. Well, (and I am sorry, I can not resist), there is some evidence to the contrary. See: http://www.w5dxp.com/energy.htm http://www.w5dxp.com/nointfr.htm ....Keith |
#117
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On Jun 2, 6:33*pm, Keith Dysart wrote:
The voltage and current distribution on a transmission line can be solved with a set of differential equations which satisfy some boundary conditions. I am not interested in voltage and current. Like optical physicists, I am only interested in tracking the RF energy flow. It does not make these waves any more real. Agreed, but the point is that it does not make the traveling waves any LESS real! I bring you back to a previous question which you have never answered... On an ideal line with 100% reflection, there are points where the current and voltage is always 0. Knowing that if either current or voltage is 0, power is also 0, how does energy cross these point? Good grief, I have answered that question at least a dozen times. The net current being zero is just an illusion caused by superposition of two magnetic fields propagating in opposite directions that are equal in magnitude and opposite in phase. The two traveling waves keep on trucking at their relatively constant ExH energy levels in opposite directions. If you want to account for the energy, when the current is zero, all of the energy existing at that point is in the electric field and, sure enough, the voltage is at a maximum at that point- duuuhhhh again. There is absolutely no point on an active transmission line where the net energy level is zero. Again, you guys are never going to convince anyone that the Golden Gate Bridge doesn't need maintenance because the net traffic on the bridge is zero. How the heck can thousands of vehicles traveling one direction while the same number of vehicles are traveling in the opposite direction add up to zero effect in reality? Please get real. And if I cut the line at all the places where the current is zero, it does not alter the energy distribution on the line one iota. How can this be if energy is travelling from end to end on the line? As I told you years ago, when you cut the line, you radically change the impedance and create a reflection that didn't exist before you cut the line. Hint: There are no reflections at a point of constant Z0. There are only reflections at an impedance discontinuity. The alteration of the energy distribution (to which you seem to be blind) can easily be observed in a TV system. PHYSICS has long given up on the idea of waves being an explanation for light. And RF waves are technically light, just not visible light. When I was rummaging through the Texas A&M library, I found a book entitled, "Light". It covered the subject of RF waves. EM waves are analog and in no way encompass the quantum nature of photons. You could become famous if you can prove that EM waves are not quantized. Good luck on that one. No one has claimed that EM waves stand still, ... Please prove your ridiculous assertion that no one has ever claimed that EM waves can stand still. -- 73, Cecil, w5dxp.com |
#118
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On Jun 2, 11:48*am, K1TTT wrote:
my differential calculus is a bit rusty, but i don't think that equation satisfies the basic wave equation. My calculus is probably a lot rustier than yours but it would be very important for this discussion if Maxwell's equations do not work for the standing wave equation. That would essentially prove that the mashed-potatoes theory of transmission line energy is bogus. -- 73, Cecil, w5dxp.com |
#119
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lu6etj wrote:
Oh!, I surrender :) The thread do not converge to a solution, it seems run out toward a naked singularity! I stay tuned until this good brainstorm calms down .. Good day Miguel, you must be new here! I don't think any threads converge to a solution. Mostly they do that singularity thing after about the third message. But hang in there, often much entertainment is to be had! |
#120
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On Jun 2, 12:56*pm, lu6etj wrote:
Oh!, I surrender *:) The thread do not converge to a solution, ... Miguel, do you fully realize the importance of Maxwell's equations being nonfunctional with the equation for standing waves? It means that any analysis based entirely on standing waves is probably invalid in some area of the analysis - probably including Keith Dysart's latest postings about the standing wave's zero current being meaningful in some way. -- 73, Cecil, w5dxp.com |
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