I think I've displayed my confidence in the physics community to appropriately put things into context - and that is a vote of no confidence! I disagree with the context in which 'particle' and 'light' were related by physicists and do not think it is necessary.
Then would you agree if I'd say that a photon is a short wave packet, that can be only absorbed as a whole? Let say that the emission of a photon from an atom lasts for some time t, then the lenght of the photon is l=ct.
fo3, No, because this way it is equivalent to a particle with electric and magnetic fields in a special structure: an "electromagnetic particle" as I say in "The photon"
It is not equivalent to a particle. A particle is not the simple definition of an 'individual entity' as you and others tend to think.
Well, I never heard about the "short wave packet" notion. Do you have some reference or is a new theory?
About light and its dual nature Well, that's very simple! A light particle is a sober light and a light wave is a drunk light! Be careful with the drunk light, cause it can break speed limits! They can also not stop at the lights! Enlighten me! Yaba Daba :m:
I don't have a specific link, but try googling for wave packet and see what can you find. I know I have read it from somewhere and I don't think that it's something new.
That's exactly right. The discrete nature displayed in the photoelectric effect is due to the atoms the light interacts with but not the light itself (which can be consistently described as an electromagnetic wave). Hence there is no duality. For more on this see my page http://www.physicsmyths.org.uk/photons.htm .
We can argue about what is the essential nature of a “particle” but I do not wish to go further than to observe that particles must have small spatial extent compared to say a high-rise apartment building. (I think most will accept that as a reasonable requirement for something being called a “particle.”) There have been comments here about “wave packets” of light. I know from direct measurements I have done that most light meets the above requirement. I am not going to assert that this fact gives light a particle status, independent of the “photoelectric effect,” but I do state that most photons are able to pass thru a needle’s eye and are less than a meter long. (Much less volume than all high-rise apartments I have seen.) WARNING: Skip this paragraph if you know little math and physics. The longer ones come for atomic transitions that have very low transition probability, well defined wavelengths, etc. - all this related to fact that the energy and time operators of quantum mechanics do not commute under the Hamiltonian and think about what the Fourier Transform of a relatively small (but still huge) number of cycles implies for the exactness of the wavelength. This BTW is why a relatively stable transition of a particular isotope of mercury was long the standard wavelength for calibrating/ measuring the diffraction grating spacing constant - perhaps it still is. There are basically two types of optical interferometers: path division and wave division. In the path division type, a beam of light is first presented to a “half silvered mirror” with part of the beam going one path and the other another way. After their separate journeys, they are recombined to display the interference pattern. It is well know that a single photon in some sense travels both paths because if the interference pattern is used to expose film, it remains unchanged even if the intensity is so low that never do two photons exist at the same time during the long exposure of the film. What will destroy the pattern in a path division interferometer is to make the difference in the two paths too great. I have done this for the sodium D lines from a modest pressure light source -It had a lot of “collision broaden” so the packet length was only about 30 cm. That is if the difference in path length was more than 30 cm, the interference was lost. It jus fades away as the path difference is increased. The head of each photo fails to over lap with its own tail which went the shorter path. That is each photon individually was an energy packet about 30 cm long. Whether or not something very small in cross section and about 30 cm long is to be called a particle or not is up to your definitions/requirement of “particle things” but for me this is clear indications, in addition to the photoelectric effect, that photons are of a nature that is not understandable by humans, Please Register or Log in to view the hidden image! only by well trained physicists. Please Register or Log in to view the hidden image! The fact that each single one of the “packets” goes by two different, well separated, paths does not help even physicists have a “warm and fuzzy feeling” about them much either. Please Register or Log in to view the hidden image!
Billy T, I disagree with this reasoning that is also found in Feynman double slit experiment. I have seen that termoionic process (simply heating of a material) are used to produce photons and the intensity is decreased untill single events are seen but this do not imply the existency of individual photons! I think that a small quantity of parallel photons are actually produced! The termoionic process is not a process that can guarantee the emission of individual photons. Then actually several photons interacts at the end to produce the interference patterns. One particle cannot travel two different paths at the same time anyway never! The principles of conservation of mass and energy are violated this way: for some time mass and energy would be duplicated!!!
And these "parallel" photons always travel such that a perfect two-slit interference pattern is built up over time? Bit of a stretch huh?
By the way,a fact nor very well known in connection with the photoelectric effect is the circumstance that the photoelectrons are emitted in the direction of the electric field vector of the light i.e. perpendicular to the direction of propagation (see http://prola.aps.org/abstract/PR/v37/i10/p1233_1 ). This clearly rules out the idea that light consists of particles as the photoelectrons would be ejected primarily in the forward direction. Also, in Quantum mechanics the interaction of light with atoms is always being treated by a perturbation theory (i.e. an atom perturbed by a sinusoidal electric field) (which by the way confirms the experimental result in the link above). On the other hand, there is no theory at all that could describe the interaction of light with atoms on the basis of a particle model (and as shown on my page http://www.physicsmyths.org.uk/photons.htm the particle model would not enable a sufficient energy transfer to the photoelectron anyway due to the small 'mass' of the photon).
Most of what you state, if not all, is based on your experience and the opinions formed from it, not derived from experments designed to try to understand how nature is in a realm where there is no human experience. I hope your mind is not so closed and small that that you deny even the possibility tht nature on the grand scale of the universe or the micro scale of the atom may be very different from any extention of your experience ("common sense") into these realms where you have no experience and must rely upon experiments to determine what is the true nature of reality. Thus, I am willing to try (but with little expectation of success), to help you understand better at least the smaller realm. Others may at least learn some of physics history especially about the revolution Planck unintentionally started. You make it quite clear that you are speaking of what is more standarly called "thermal emission" but I only mention this to help you comunicate withothers. What you call it is of no importance to your idea expressed. Almost all physicsis, perhaps it is accurate to say ALL physicists, held your view in 1900. But a few, mainly those well versed in what we now call "statistic mechanics" and thermodynamics recongized that physics had an inconsistencey in it: (1) Maxwell's equations due not have either any upper limit on the frequency of EM waves (and indeed gamma "rays" - terrible misnomer as they are EM waves of very high frequency) have been observed. OR any discreteness to the frequency I.e. no matter how small "e" is, there is a frequency f and also a frequency (f+e). We call this a "continuium." Before giving the other half of the conflict (2), I want to introduce the concept of "modes" to you. You no doubt know that the strings of a violin can oscillate in only certain "pure" notes. The lowest note of a string is produced when all parts of the string are moving in the same direction. that is the "fundamental mode" the next mode it when one half of it is moving in the opposite direction from the other. etc. (2) In several fields of physics in 1900, especially stastical mechanics theory and thermodynamics, both of which had had great success with things related to temperature, killed the old fluegiston theory, etc., it was well established that, in equlibrium, each "mode" possible would have the same energy. "Equal partition of energy" was a pharse that rolled out of the mouths of well informed people (not just physicists) as easily as "conservation of energy" does today. The conflict was that there are and infinite number of frequencies (modes) predicted by Maxwell's equations. Every one agreed that the interior of a hollow box whose exterior wall's temperature was held constant for a long time would be in "thermal equlibrium" and filled with Maxwell's EM waves, that is filled with thermal radiation. Surely if only a very small hole (compared to the total surface of the interior chamber), were drilled into the box and one looked to see the nature of this radiation it would not disturb it significantly. Well, when this was done and the distrubition of the radiation coming from a copper box , a steel box, a white ceramic box, a tin box, a gold box, etc. was measured, there was a shock - a conflict among well established theories. The minor problem was that it made no difference what the box was made of. The relative strength of different wavelengths in emerging from the box was always the same! How was this possible when gold and white ceramic and steel all reflect (interact with light to speak more generally) so very differently? But to serious thinking physicists, this was a small problem - Where were the high frequency modes? That was the real mystery. They was no UV radiation. Why was "equal partition of energy" failing? This was not just a problem - it was a catstrophy for their well established theories. In fact, it was refered to as the "Ultra Violet catastrophy." Only the best minds of the day even tried to resolve this conflict without destroying all that was known. Planck made a silly assumption - He said: lets assume that light (radiation) is not truely a continuium when inside or comming out of a finite size box. (In terms of the "e" and (f+e) he was postulating that "e" can only be so small and no smaller! (This is contrary to all commons sense and human experience. - It was as if some blue/green light could not be arbitarily a little more blue - and a little less green as it could be according to everyone's experience, or "common sense" tells it could be.) This ridiculious assumption by Planck was the begining of the end of the world as you imagine it and the start of the recognition that the very small and very large can be vastly different than the ordinary world we experience and base our opinions on. Planck was a good mathematician, and he ground thru the math to see what the consequence of this crazy idea would be. Supprize, supprize, that crazy idea predicted (1) exactly the relative strength of the different wavelengths coming out of the box, (2) which would be the strongest one, (3) how the total energy would change with temperature (by the fourth power), (4) that the strongest one would shift in frequency linearly with the absolute temperature, (5)that what the walls were made of would not change any of this. I.e. all the observed facts. It was a real revolution, not just in physics, but in the thought patterns of all inteligent, well educated people. Intelligent people began to understand that their experience and common sense is useless when applied to the very small and the very large. - Only experiments will permit us to test "crazy nonsense theories" to see if they are really true. I hope some day you will join this revolution and realize that what you think must be true, based on common sense, is not necessarly true. Based on common sense, a single photon can not go by two separate paths. If it did and only one half were absorbed, then the other half would need to change color to conserver energy etc. (energy of photo is directly related to frequency or color) etc. There are dozens of common sense reasons "proving" that a single photon can not go thru two different slits or by two different paths, but unfortunately nature has no common sense and does as she does in violation of it. Quantum mechanics grew out of Planck's "crazy idea". Quantum mechanics is probably the most successful physics theory ever invented. Thousands of entirely different predictions have been tested and all confirm it. For example, with only math and the quantum theory, you (if you are good in math) can calculate the energy levels of the hydrogen atom and predicts between which transitions are permited and between which they are not. Then go in the lab and observer the spectrial radiation coming from hydrogen (The "Lyman series" of lines predicted is in the UV and the Balmer series in the visible.) Not only are only the predicted lines and only them the ones observed, but the predicted wavelengths observed are exatly (well at least to the experimental accuracy possible, which is about + or - 0.000,000,1 %) the value predicted. I think the "fine structure constant," which happens to have important theoretical implications, has been calculated to more places than most, if not all other values, predicted by QM. (Even if the theory is perfect, which it sure seems to be, you must take care when calculating using digital computers as they only have accuracy to about 64 decimal places and errors can accumulate during the calculations.) Let me close by again expressing my hope that you will join Planck's revolution - that is recognize that EXPERIMENTS, not COMMON SENSE, tell how nature is in the realm of the very small or the very large. If you do, then abandon your false, common sense based, statement:
It is true that the discrete nature of the photodetection process arises, at least in part, from the quantum mechanical nature of the atom which interacts with the electromagnetic field. In other words, if I shine classical light on a photodetector, I still get single pulses in principle, though this may be difficult to see because intense light will trigger many pulses. However, as I decrease the intensity, I must use the quantum theory of light. This theory, which has been shown in many experiments to correctly describe light, indicates that it is possible to produce a quantum state for light which can only produce one photopulse. No classical wave theory has reproduced this result. We call these one pulse only states single photon states. We can take one of these single photon states, pass it through a beam splitter, and then observe the coincidence correlation function between detectors in the two arms of the beam splitter. What do we find? We find that the single photon state cannot trigger both detectors simultaneously and that the second order coherence is below the classical limit.
I of course agree with all you have said, because it is true. To state it again (without using the word "correlation" or other more sophisticated concepts): When the photon is detected, it is either found to be in "arm A" of the split path, or "arm B." Furthermore, if paths A & B are brought back together to make an interference pattern on a screen, and you try to "cheat" by placing some detector in one of the paths that only reflects the photon but allows you to measures the recoil it makes when reflected and thus know which of the two paths the photon actually took. I.e. try to know which path (your common sense tells you there is only one) then the interference pattern is destroyed because you have "localized the photon". Now a personal word about my Ph. D thesis experiment. After about a year of working I was able to make a hot plasma so reproducably in a "shock tube" that the oscillascope traces recording a particular spectral line from one shock fell exactly on top of the ones formed in prior shocks. For my Ph.D., I was measuring the shape and slight displacement of some argon ion lines in a plasma with an ordinary spectrograph to separate out the line of interest and a Fabry-Perot interferometer to split the individual line into dozens of separate spectral bands, each having its intensity measured separately. Even though the shock was extremely bright to the eye, when only such small spectral bands were allowed to reach my photomultiplier tube detector, the oscillascope traces no longer fell on top of each other, one shock compared to another. When I worked the gain of the of the PM tube (which is not a constant as each electrode stage may multiply the number of electrons incident differently each time itis called to do so) backwards, I realized the non reproducibility problem was "shot noise." That is, the number of photons surviving the high spectral resolution I was using from even this very bright source was only 5 or 10 when I was out in the "wings" of the line shape. Thus I personnally have seen that photons are individual and if you are at such low intensity levels, there is a "shot noise" vairation in exactly how many exist in a brief time period.
Billy T, interesting experiment. I tend to agree. The occurrence of shot noise in quantum optical systems is significant because it arises from the discrete nature of photons just as shot noise in electric circuits comes from the discrete nature of the electrons making up a current. The low intensity noise properties of quantum optical systems are really a fascinating area of study.
Billy T, I totally agree with Planck theories!!! I totally agree with Quantum Physics!!! I disagree with Wave Mechanics!!! I think that Wave Mechanics is the theory that allows that uncertainity about the existence of matter in a determined place and is the base of your statement. I didn't talk about common sense, I said that the assumption of the possible travel of a particle in two different paths at the same time violates at a first approach the principles of conservation of mass and energy. I realize now that it can be proposed that the particle is not at two places at the same time but alternates between two possible places "statistically" and the principles of conservation of mass and energy are not violated. I believe this is what Wave Mechanics can predict for the experiment with a single photon... I do not disagree with Planck and his Quantum Physics but I disagree with Wave Mechanics. You can easily see this at my site: "A New Light In Physics" I have just presented another interpretation for the experiment you mentioned and that is similar to the Feynman double slit experiment. I propose that actually bursts of parallel photons are emitted in the "thermal emission" process and that they separate to travel different paths and join again with different phases and produce the interference patterns as I describe in Section 4.2: "The photon interference and diffraction" for photons and in Section 4.5: "The electron diffraction" for electrons. I do believe that the "thermal emission" is a process that cannot guarantee the emission of individual photons, not even in the case where the intensity is decreased untill discrete events are seen ("shot noise"?). I propose that actually bursts of parallel photons are emitted in that case what is very reasonably and allows a proper explanation of the interference patterns.
In the case of the photoeletric effect, the amount and energy of the photons can be easily measured by registrating the electrons that escape from the atoms. If there are more then one photons then there must be more then one photoelectrons aswell. The burtst of parallel photons could be easily distinguished. Why do you find it so difficult to accept the widely accepted and confirmed theories? You know, people wont laugh at you if you say that you have realised that you had some of your ideas weren't correct. I bet most of them would be happy to see that.
No that (uncertainity principle etc.) is quantum mechanics result. I do not know of any thing called "wave mechnics." Maxwell's equations describe all EM waves and QM all others, expect ware waves, sound waves etc are highlevel (macro) applicatins of QM and QM is never actually actually used for these waves but could be by the "correspondence princile of QM.
fo3, May be is easy but it does not appear to be done in any description of this kind of experiments, for example in the Feynman double slit experiment. It is not being done although it should be done... If there is anything that at some time I really realize that there is something wrong I will accept, recognize and correct it, I will have no problem. The theories were developed that way! I mean: proposing, verifying, checking and going back and correcting them whenever it was necessary and I had to go back, think different and go on again many, many times.
