-
#640 by Notsosureofit on 01 Nov, 2018 16:54
-
FYI: https://arxiv.org/pdf/1707.01345.pdf
Axion Mass Bound in Very Special Relativity
"First, we have considered the inverse Primakoff process, the production of axions
due to a photons source. In this case, we have fully established the axion field solution in the
presence of an external magnetic field."
-
#641 by spupeng7 on 02 Nov, 2018 02:14
-
X_Ray,... if reflection is emission following absorption...
I guess you're confused about the photoelectric effect that doesn't occur at "low" frequencies (2.4 GHz), as discussed for the EM drive, or by Fluorescence (Fluorescence is simply defined as the absorption of electromagnetic radiation at one wavelength and its reemission at another, lower energy wavelength.)
Photons re emitted from atoms will have discrete frequencies governed by the change of the energy state of the corresponding electron. This is why we can get exact "fingerprints" for each chemical element.
Quote from: wikipediaFeynman diagram on the photoelectric effect: An electron electrically bound to an atom {Z} interacts with a photon and changes its energy.
In contrast the reflection of microwaves at conductive boundaries is well described in the link below and elsewhere.
https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-007-electromagnetic-energy-from-motors-to-lasers-spring-2011/lecture-notes/MIT6_007S11_lec29.pdf... then the end with the ring structures will delay the reflection and retain the momentum of the resonant energy for longer than the end without them (because the conductive path is longer). ...
More metal at one end leads to bigger dissipative loss at this location because of its finite resistance.
There is no delay involved but a different impedance and scattering conditions due to the structures as compared to the flat end.... In a Machian universe of charge interactions this is a direct mechanism for acceleration of the whole mass of the device, non?
How does that follow from the rest of your post?
the photo electric effect describes the process where an atom releases an electron as it absorbs a quantum of sufficient energy to cause that to happen, an entirely different mechanism to reflection. Nothing in the reference you gave suggests a mechanism for reflection but only describes the mathematical knowns of those interactions in language strictly limited to a perspective which denies the common mechanism of electrical and magnetic phenomena.
All reflection must involve absorption and emission of the incident radiation, otherwise it would not involve the reflective surface at all, which it must.
To quote myself,
'There are some things we can say about reflection with confidence, most of which were described by Newton himself. The angle of reflection from a polished flat is equal to the angle from which the light comes and it stays in a plane at right angles to the surface. The colours reflected are the colours incident minus any which are absorbed or transmitted through the material, reflection does not change the wavelength of light. All materials become transparent if they are made thin enough, even gold which transmits blue light. And, reflection from a flat increases with the angle of incidence so that reflection becomes complete as the incident ray approaches a path parallel to the surface. “In this Proposition I content myself to have put it past dispute, that Bodies have such Properties…” Newton ‘Opticks’ 1675.
But, there are questions raised by Newton which remain a mystery. Not least of which is the comparison between reflection from a polished metal surface and the reflection from a transparent layer. The polished metal surface is reflective irrespective of what is behind it but a layer of transparent material will reflect light only when its thickness is some multiple of the wavelength of the light in that material. These appear to be two completely different mechanisms for reflection, the first a reflection involving absorption and emission, the second just a constructive interference. As with all particle interactions, macroscopic analogies are poorly matched to the infinitesimal world. There are important lessons for us here. Our human perspective leads us to certainty where logic seems complete but faith in physical interpretations is often premature.'
From my article 'Reflections on Reflection' Published in the ASSA Bulletin August 2012, also in Sagittarius (newsletter of the Astronomy Section of La Société Guernesiaise) April 2012
The reflected energy of light is contained, if temporarily, within the surface reflecting it, without any electrons necessarily being dislodged from their atoms. How else would reflection work? -
#642 by meberbs on 02 Nov, 2018 17:58
-
the photo electric effect describes the process where an atom releases an electron as it absorbs a quantum of sufficient energy to cause that to happen, an entirely different mechanism to reflection.
That seems to have been the point, reflection and absorption are fundamentally different, but you were interchanging them.Nothing in the reference you gave suggests a mechanism for reflection but only describes the mathematical knowns of those interactions in language strictly limited to a perspective which denies the common mechanism of electrical and magnetic phenomena.
No, his reference uses standard electromagnetism. There are other sources out there that go into more detail, but the reference does describe the basics of how it works.All reflection must involve absorption and emission of the incident radiation, otherwise it would not involve the reflective surface at all, which it must.
False, there are other mechanisms of interaction than "absorption and emission."The colours reflected are the colours incident minus any which are absorbed or transmitted through the material, reflection does not change the wavelength of light.
False, this is frame dependent. Your statement only holds in a frame where the kinetic energy of the reflecting surface is unchanged.All materials become transparent if they are made thin enough, even gold which transmits blue light.
What are you talking about? Gold doesn't just transmit blue light, a thin gold coating transmits broad spectrum optical light. It is much more reflective at IR than visible, which is why it is a good choice for coating astronaut visors.But, there are questions raised by Newton which remain a mystery. Not least of which is the comparison between reflection from a polished metal surface and the reflection from a transparent layer. The polished metal surface is reflective irrespective of what is behind it but a layer of transparent material will reflect light only when its thickness is some multiple of the wavelength of the light in that material. These appear to be two completely different mechanisms for reflection, the first a reflection involving absorption and emission, the second just a constructive interference.
They are different mechanisms, but there is no mystery, and neither is "absorption and emission." Take a look at some of the other slides in the lecture series X_RaY linked. Sections 30, 32, and 33 are relevant at least. (You can also look elsewhere, since that series seems intended to have a professor talking to the slides and filling in some of the not explicitly stated information.)The reflected energy of light is contained, if temporarily, within the surface reflecting it, without any electrons necessarily being dislodged from their atoms. How else would reflection work?
It would work according to the description that you can find in any descent text book. The incident fields induce currents on the surface. These currents immediately reflect the energy back in the other direction. There is no absorption and emission in the way you are describing it, and even if there was (say we were talking about a fluorescent surface) that would still not produce any sort of imbalance in inertia. -
#643 by X_RaY on 03 Nov, 2018 22:11
-
Thank you Meberbs, your mind is very sharp and I can't say anything more useful than what you are saying in this regard!the photo electric effect describes the process where an atom releases an electron as it absorbs a quantum of sufficient energy to cause that to happen, an entirely different mechanism to reflection.
That seems to have been the point, reflection and absorption are fundamentally different, but you were interchanging them.Nothing in the reference you gave suggests a mechanism for reflection but only describes the mathematical knowns of those interactions in language strictly limited to a perspective which denies the common mechanism of electrical and magnetic phenomena.
No, his reference uses standard electromagnetism. There are other sources out there that go into more detail, but the reference does describe the basics of how it works.All reflection must involve absorption and emission of the incident radiation, otherwise it would not involve the reflective surface at all, which it must.
False, there are other mechanisms of interaction than "absorption and emission."The colours reflected are the colours incident minus any which are absorbed or transmitted through the material, reflection does not change the wavelength of light.
False, this is frame dependent. Your statement only holds in a frame where the kinetic energy of the reflecting surface is unchanged.All materials become transparent if they are made thin enough, even gold which transmits blue light.
What are you talking about? Gold doesn't just transmit blue light, a thin gold coating transmits broad spectrum optical light. It is much more reflective at IR than visible, which is why it is a good choice for coating astronaut visors.But, there are questions raised by Newton which remain a mystery. Not least of which is the comparison between reflection from a polished metal surface and the reflection from a transparent layer. The polished metal surface is reflective irrespective of what is behind it but a layer of transparent material will reflect light only when its thickness is some multiple of the wavelength of the light in that material. These appear to be two completely different mechanisms for reflection, the first a reflection involving absorption and emission, the second just a constructive interference.
They are different mechanisms, but there is no mystery, and neither is "absorption and emission." Take a look at some of the other slides in the lecture series X_RaY linked. Sections 30, 32, and 33 are relevant at least. (You can also look elsewhere, since that series seems intended to have a professor talking to the slides and filling in some of the not explicitly stated information.)The reflected energy of light is contained, if temporarily, within the surface reflecting it, without any electrons necessarily being dislodged from their atoms. How else would reflection work?
It would work according to the description that you can find in any descent text book. The incident fields induce currents on the surface. These currents immediately reflect the energy back in the other direction. There is no absorption and emission in the way you are describing it, and even if there was (say we were talking about a fluorescent surface) that would still not produce any sort of imbalance in inertia.
However, I thought about whether I should post the following or not. This is not a course in basic physics, but it sometimes seems necessary to use simple words when talking to the public.
I will try to do so using words to explain what happens when an EM-wave is reflected at a conductive material.
First of all it should be clear that the crystals based on metal atoms consist mainly of empty space, its not a surface in the classical sense if we take a look at the atomic scale. However, the space between the atomic bodies is filled by the electromagnetic fields of the protons and electrons, where the electrons are the important part if we want to explain the reflection, therefore lets focus on the electron shells of the atoms only. Also important is the knowledge of Valence and conduction bands that exists in conductive materials.
OK, let's move on to the verbal explanation:
The electromagnetic field of the incident EM wave interacts with the field of the electrons in the conducting volume(to the first order), especially with the free moving valence electrons in the conduction band. The external variation field (here especially the magnetic component) induces a current in the conductor, it moves the electrons. These mobile charges are now themselves a source of a magnetic field since moving electrically charged particles generate a magnetic field. This field acts exactly against the incoming wave, its vectors are directed against the incoming field. The fields repel each other. This causes the wave to be reflected.
Of course the wave loses some energy during the reflection by the ohmic loss in the conductor, which affects the moving electrons.
Perhaps it is helpful for some interested spirits to use such an explanation to recognize what is happening instead of using the corresponding equations? -
#644 by Mulletron on 03 Nov, 2018 22:49
-
Some news.
https://www.popularmechanics.com/space/rockets/amp24219132/darpa-emdrive/
There's a lot to unpack in the article such as this:QuoteFiddy confirms that DARPA has previously funded work related to the EmDrive
I wonder what that was about.QuoteDARPA's $1.3 million contract includes developing theories to reconcile the EmDrive with known physics
I find it interesting that they're interested in developing a theory. That alone isn't interesting except that it implies that there's a good enough reason to develop a theory in the first place, such as convincing experimental results. There's plenty of known non Newtonian physics.Quote“If DARPA does not gather this evidence and publish the results, positive or negative, then who in the U.S. government will?”
What about the NRL?Quote“The idea not only violates Newton’s third law of motion, it violates special relativity, general relativity, and Noether’s theorem. Since these are each well-tested theories that form the basis of countless other theories, their violation would completely overturn all of modern physics.”
Yes it would appear to do so, if you think like this:QuoteHere's how the EmDrive works. Imagine you have a truncated cone—a tube wider at one end than the other—made of copper. Seal it, then fill it with microwaves. Like other electromagnetic radiation, microwaves exert a tiny amount of pressure. But because of the shape of this device, they would exert slightly more force on one end than the other. So, even though it’s a closed system, the cone would experience a net thrust and, if you had enough microwaves, it would gradually accelerate.
-
#645 by 1 on 04 Nov, 2018 05:40
-
I will try to do so using words to explain what happens when an EM-wave is reflected at a conductive material.
X_RaY, meberbs:
Although your posts on the subject are quite good, I don't believe the root issue of spupeng7's question stems from a misunderstanding of what reflection is. Rather, it's another variation of the old mistake of calculating the movement of cavity structure alone rather than the movement the entire system.
Spupeng7, although I do suggest looking through slides X_RaY linked to, you're asking a question that we've seen many variations of over the years. If, instead of photons, you use balls with a small mass, then it becomes straightforward to see that by "retaining" them at one end for some finite time, you've concentrated a finite amount of mass in a location that was empty before you turned on your system. A forward shift in the cavity wall is countered by a rearward shift of the small but massive balls towards the retaining end. Your center of mass, your system as a whole, does not move.
The difference between massive balls and photons is merely one of habit and convenience. We can usually ignore energy density in classical mechanics because photonic momentum kicks are so small. However in this situation (assuming no new physics), E&M is all we have. So a proper treatment needs to track the energy before conversion to, and after conversion from, propagating E&M forms. The normally-useful approximation that photons simply came into being during antenna transmission, and ceased to be once absorbed is no longer valid. A forward shift in the cavity, in your example, is countered by a rearward shift in energy density.
To better visualize this, forget the ring structure or any notion of delayed reflection altogether and just assume the rear wall of the cavity is perfectly absorbing. Paint it Spinal-Tap black. What happens? Well, as energy concentrates in the rear wall, it will get hotter. Though it no longer emits pure RF, it will emit blackbody radiation; complete with all of the rearward momentum kicks from those newly emitted photons. The amount of time it takes to heat up can be arbitrarily short or arbitrarily long (high retention and low retention, respectively); the end result is the same. Eventually, energy density shifts back forward. The cavity itself shifts backwards, and the system as a whole stays right where it started. -
#646 by Monomorphic on 04 Nov, 2018 21:52
-
I find it interesting that they're interested in developing a theory. That alone isn't interesting except that it implies that there's a good enough reason to develop a theory in the first place, such as convincing experimental results. There's plenty of known non Newtonian physics.
Mike Fiddy made it clear during his presentation at Estes Park that DARPA would like to see more modeling of the different theories. This includes the mach effect and quantized inertia. I understood this to be computational models that make specific predictions that can be compared with observation. For example, if Mike McCulloch could show that his theory, when modeled, can also simulate the large scale structure of the universe, then that would be very convincing as current dark matter models require some arbitrary finessing to get the same results. -
#647 by Amit on 05 Nov, 2018 05:07
-
http://theoryofsuperunification-leonov.blogspot.com/
http://leonov-leonovstheories.blogspot.com/
Results of measurement of the specific thrust force of the quantum engine
If anyone has looked at this? Is this similar to EM Drive? Is this pseudoscience? Profile says Dr. V. Leonov was awarded a Russian government prize in the area of science and technology and in 2007 was included in 100 leaders of science and technology of CIS countries. -
#648 by TheTraveller on 05 Nov, 2018 13:39
-
https://www.popularmechanics.com/space/rockets/amp24219132/darpa-emdrive/
Seems DARPA have decided to re engage with Roger Shawyer and deal direct instead of using Boeing as an intermitetary. See attachment.
https://www.darpa.mil/program/nascent-light-matter-interactions
"Examples of these novel phenomena include interactions involving active media, symmetry, non-reciprocity, and linear/nonlinear resonant coupling effects.
Insights regarding the origins of these interactions have the potential to transform our understanding of how to control electromagnetic waves and design for new light-matter interactions. "
https://www.darpa.mil/news-events/2017-11-15
"Because of these intricate internal and surface structures, new properties have emerged, some exhibiting behavior that has resulted in rewriting long-understood “laws” for how light and other electromagnetic (EM) waves interact with materials."
-
#649 by Star One on 05 Nov, 2018 20:12
-
New physics anyone?
Mystery particle spotted? Discovery would require physics so weird that nobody has even thought of itQuoteThe new result – consisting of a mysterious bump in the data at 28 GeV (a unit of energy) – has been published as a preprint on ArXiv. It is not yet in a peer-reviewed journal – but that’s not a big issue. The LHC collaborations have very tight internal review procedures, and we can be confident that the authors have done the sums correctly when they report a “4.2 standard deviation significance”. That means that the probability of getting a peak this big by chance – created by random noise in the data rather than a real particle – is only 0.0013%. That’s tiny – 13 in a million. So it seems like it must a real event rather than random noise – but nobody’s opening the champagne yet.
QuoteSo it is all looking rather intriguing, but, history has taught us caution. Effects this significant have appeared in the past, only to vanish when more data is taken. The Digamma(750) anomaly is a recent example from a long succession of false alarms – spurious “discoveries” due to equipment glitches, over-enthusiastic analysis or just bad luck.
This is partly due to something called the “look elsewhere effect”: although the probability of random noise producing a peak if you look specifically at a value of 28 GeV may be 13 in a million, such noise could give a peak somewhere else in the plot, maybe at 29GeV or 16GeV. The probabilities of these being due to chance are also tiny when considered respectively, but the sum of these tiny probabilities is not so tiny (though still pretty small). That means it is not impossible for a peak to be created by random noise.QuoteIf this particle really exists, then it is not just outside the standard model but outside it in a way that nobody anticipated. Just as Newtonian gravity gave way to Einstein’s general relativity, the standard model will be superseded. But the replacement will not be any of the favoured candidates that has already been proposed to extend standard model: including supersymmetry, extra dimensions and grand unification theories. These all propose new particles, but none with properties like the one we might have just seen. It will have to be something so weird that nobody has suggested it yet.
QuoteLuckily the other big LHC experiment, ATLAS, has similar data from their experiments The team is still analysing it, and will report in due course. Cynical experience says that they will report a null signal, and this result will join the gallery of statistical fluctuations. But maybe – just maybe – they will see something. And then life for experimentalists and theorists will suddenly get very busy and very interesting.
-
#650 by spupeng7 on 05 Nov, 2018 23:39
-
Thanks meberbs,the photo electric effect describes the process where an atom releases an electron as it absorbs a quantum of sufficient energy to cause that to happen, an entirely different mechanism to reflection.
That seems to have been the point, reflection and absorption are fundamentally different, but you were interchanging them.Nothing in the reference you gave suggests a mechanism for reflection but only describes the mathematical knowns of those interactions in language strictly limited to a perspective which denies the common mechanism of electrical and magnetic phenomena.
No, his reference uses standard electromagnetism. There are other sources out there that go into more detail, but the reference does describe the basics of how it works.All reflection must involve absorption and emission of the incident radiation, otherwise it would not involve the reflective surface at all, which it must.
False, there are other mechanisms of interaction than "absorption and emission."The colours reflected are the colours incident minus any which are absorbed or transmitted through the material, reflection does not change the wavelength of light.
False, this is frame dependent. Your statement only holds in a frame where the kinetic energy of the reflecting surface is unchanged.All materials become transparent if they are made thin enough, even gold which transmits blue light.
What are you talking about? Gold doesn't just transmit blue light, a thin gold coating transmits broad spectrum optical light. It is much more reflective at IR than visible, which is why it is a good choice for coating astronaut visors.But, there are questions raised by Newton which remain a mystery. Not least of which is the comparison between reflection from a polished metal surface and the reflection from a transparent layer. The polished metal surface is reflective irrespective of what is behind it but a layer of transparent material will reflect light only when its thickness is some multiple of the wavelength of the light in that material. These appear to be two completely different mechanisms for reflection, the first a reflection involving absorption and emission, the second just a constructive interference.
They are different mechanisms, but there is no mystery, and neither is "absorption and emission." Take a look at some of the other slides in the lecture series X_RaY linked. Sections 30, 32, and 33 are relevant at least. (You can also look elsewhere, since that series seems intended to have a professor talking to the slides and filling in some of the not explicitly stated information.)The reflected energy of light is contained, if temporarily, within the surface reflecting it, without any electrons necessarily being dislodged from their atoms. How else would reflection work?
It would work according to the description that you can find in any descent text book. The incident fields induce currents on the surface. These currents immediately reflect the energy back in the other direction. There is no absorption and emission in the way you are describing it, and even if there was (say we were talking about a fluorescent surface) that would still not produce any sort of imbalance in inertia.
you are right, I did not stop to think about scattering etc before I posted that. I have a question; incident fields may be immediately reflected by the currents they engender when their wavelength is a small fraction of the extent of the reflective surface, but when their wavelength is similar to the extent of the reflective surface, is it possible that the rapidity of that reflection is somehow proportional to the extent of the reflective surface?
Edit: thanks also for the references. -
#651 by otlski on 05 Nov, 2018 23:45
-
Just who is DARPA giving $1.3 million to?
I read DARPA's position to be 'it is worth $1.3 million in chump change to ensure we cannot possibly get surprised by the small chance that the EM drive is for real coming to fruition'. -
#652 by Monomorphic on 05 Nov, 2018 23:55
-
Just who is DARPA giving $1.3 million to?
I read DARPA's position to be 'it is worth $1.3 million in chump change to ensure we cannot possibly get surprised by the small chance that the EM drive is for real coming to fruition'.
DARPA is giving $1.3m to Mike McCulloch's group for his "quantized inertia" theory research.
Your reading of DARPA's position is exactly what I took away from the presentation at Estes Park. Mike Fiddy even said they like it when the results are negative, because that means our potential adversaries are not onto something novel that could be used against us. -
#653 by spupeng7 on 05 Nov, 2018 23:56
-
Just who is DARPA giving $1.3 million to?
To Mike McCulloch at the University of Plymouth in the UK, for development of his quantized inertia theory.
I read DARPA's position to be 'it is worth $1.3 million in chump change to ensure we cannot possibly get surprised by the small chance that the EM drive is for real coming to fruition'. -
#654 by meberbs on 06 Nov, 2018 00:00
-
Thanks meberbs,
The overall effect of the reflection becomes different in that case (in part because the width of the incoming energy would be guaranteed to spillover and go around the reflector.) But the time scale it takes effect on would not change. It makes certain things harder to work out, since rather than a nice clean reflection, you also have spillover and such which could cause other interference effects depending on the shape.
you are right, I did not stop to think about scattering etc before I posted that. I have a question; incident fields may be immediately reflected by the currents they engender when their wavelength is a small fraction of the extent of the reflective surface, but when their wavelength is similar to the extent of the reflective surface, is it possible that the rapidity of that reflection is somehow proportional to the extent of the reflective surface?
Edit: thanks also for the references. -
#655 by spupeng7 on 06 Nov, 2018 00:26
-
In my opinion, understanding this is central to understanding the mechanism of action of the emdrive. None of the other theory discussed on this forum is as close to the coalface of this investigation.Thanks meberbs,
The overall effect of the reflection becomes different in that case (in part because the width of the incoming energy would be guaranteed to spillover and go around the reflector.) But the time scale it takes effect on would not change. It makes certain things harder to work out, since rather than a nice clean reflection, you also have spillover and such which could cause other interference effects depending on the shape.
you are right, I did not stop to think about scattering etc before I posted that. I have a question; incident fields may be immediately reflected by the currents they engender when their wavelength is a small fraction of the extent of the reflective surface, but when their wavelength is similar to the extent of the reflective surface, is it possible that the rapidity of that reflection is somehow proportional to the extent of the reflective surface?
Edit: thanks also for the references. -
#656 by RERT on 06 Nov, 2018 11:09
-
In my opinion, understanding this is central to understanding the mechanism of action of the emdrive. None of the other theory discussed on this forum is as close to the coalface of this investigation.Thanks meberbs,
The overall effect of the reflection becomes different in that case (in part because the width of the incoming energy would be guaranteed to spillover and go around the reflector.) But the time scale it takes effect on would not change. It makes certain things harder to work out, since rather than a nice clean reflection, you also have spillover and such which could cause other interference effects depending on the shape.
you are right, I did not stop to think about scattering etc before I posted that. I have a question; incident fields may be immediately reflected by the currents they engender when their wavelength is a small fraction of the extent of the reflective surface, but when their wavelength is similar to the extent of the reflective surface, is it possible that the rapidity of that reflection is somehow proportional to the extent of the reflective surface?
Edit: thanks also for the references.
It's been observed that the surface currents causing the reflected wave are due to motion of electrons induced by the incident wave. Since the electrons are massive, they take time to accelerate. There must be parallel electric fields in the surface to move the electrons, and there will be delays in the reflected wave caused by their acceleration time. It's a very small effect, but I haven't heard any suggestion that it is captured by modelling software. -
#657 by dustinthewind on 06 Nov, 2018 15:20
-
In my opinion, understanding this is central to understanding the mechanism of action of the emdrive. None of the other theory discussed on this forum is as close to the coalface of this investigation.Thanks meberbs,
The overall effect of the reflection becomes different in that case (in part because the width of the incoming energy would be guaranteed to spillover and go around the reflector.) But the time scale it takes effect on would not change. It makes certain things harder to work out, since rather than a nice clean reflection, you also have spillover and such which could cause other interference effects depending on the shape.
you are right, I did not stop to think about scattering etc before I posted that. I have a question; incident fields may be immediately reflected by the currents they engender when their wavelength is a small fraction of the extent of the reflective surface, but when their wavelength is similar to the extent of the reflective surface, is it possible that the rapidity of that reflection is somehow proportional to the extent of the reflective surface?
Edit: thanks also for the references.
It's been observed that the surface currents causing the reflected wave are due to motion of electrons induced by the incident wave. Since the electrons are massive, they take time to accelerate. There must be parallel electric fields in the surface to move the electrons, and there will be delays in the reflected wave caused by their acceleration time. It's a very small effect, but I haven't heard any suggestion that it is captured by modelling software.
I think the modeling software catches it at the moment of equilibrium and is time averaged. That moment the friction slowing the electrons matches the input energy keeping them at equilibrium. There might be some small effect due to the friction [inducing thermal effects where thermal radiation transmits through the entire material] but it's small compared to the stored energy of a high Q cavity.
Edit:
I almost forgot to emphasize that half of the energy in the cavity is in the magnetic field. The magnetic field is what's up against the skin of the cavity. A changing magnetic field induces an electric field. These electrons see the changing magnetic field has an electric field. In a sense they see both electric and magnetic field. They see this Electro-magnetic field as moving at the speed of light. During their acceleration the electromagnetic field they emit cancels the electric field of the incoming light while constructively enhancing the magnetic field when they are free to accelerate. The skin depth for this to happen is what contains the radiation inside the cavity.
The time to reflect I think has to do with penetration depth which depends on the frequency. https://en.wikipedia.org/wiki/Penetration_depth
also related:
googled "time to reflect penetration depth"
https://www.fer.unizg.hr/_download/repository/1992_JQE_v28_n02_Babic_Corzine.pdf
Analytic Expressions for the Reflection Delay,
Penetration Depth, and Absorptance of
Quarter-Wave Dielectric Mirrors
Dubravko I. Babic and Scott W. Corzine
Quote...In this paper we derive expressions for the penetration depth and mirror reflection delay that are valid for arbitrary material refractive index combinations and any number of layers... ...the reflection delay adds to the laser cavity roundtrip
time.
So there does appear to be a time delay in reflection via skin depth where I think the first electrons are not capable of totally reflecting the entire signal via resistance and I think mass. As a new change in power or a beam of light coming in has both electric and magnetic field then yes there would be some electric field penetration into the surface of the material. -
#658 by meberbs on 06 Nov, 2018 15:44
-
It's been observed that the surface currents causing the reflected wave are due to motion of electrons induced by the incident wave. Since the electrons are massive, they take time to accelerate. There must be parallel electric fields in the surface to move the electrons, and there will be delays in the reflected wave caused by their acceleration time. It's a very small effect, but I haven't heard any suggestion that it is captured by modelling software.
The effect of reflection happens due to the changing currents, the acceleration itself. This means that the finite mass of the electrons does not delay the effect.
There are electric fields that penetrate due to the finite conductivity, but the depth is small, and effectively changes the cavity shape by less than the manufacturing tolerance for most cavities anyway. -
#659 by X_RaY on 06 Nov, 2018 20:20
-
Totally agreeable, butIt's been observed that the surface currents causing the reflected wave are due to motion of electrons induced by the incident wave. Since the electrons are massive, they take time to accelerate. There must be parallel electric fields in the surface to move the electrons, and there will be delays in the reflected wave caused by their acceleration time. It's a very small effect, but I haven't heard any suggestion that it is captured by modelling software.
The effect of reflection happens due to the changing currents, the acceleration itself. This means that the finite mass of the electrons does not delay the effect.
There are electric fields that penetrate due to the finite conductivity, but the depth is small, and effectively changes the cavity shape by less than the manufacturing tolerance for most cavities anyway.
with 'α' as the angle between the longitudinal direction of the conductor and the direction of the magnetic flux density vec _B.
I'm sticking with it since the electrical field component is negligibly small within the conductive wall, therefore the reason of the force acting on the electrons must the magnetic field and the associated Lorentz force which triggers the charge carrier movement to the first approximation.
However, I fully agree with meberbs regarding the scattering conditions described in the message written by spupeng7.
The electric field within the skin penetration depth exists but again - it is negligible - regarding its field strength.
