Discussion in 'Physics & Math' started by Vern, Aug 31, 2006.
DaleSpam; are you sure you are not confusing your ability to know with what is real.
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If they are "planes" why not call them that? E.g. the plane of the E field oscillation - "flux" is very confusing. Aslo, just to be sure, this "distance away" is measured transverse to the path of photon, I am assuming, but is there any angular dependency wrt the E field plane? how important is a location directly on the path of photon but "miles ahead" of it curent location?
By center of the photon do you mean one point or the line of its path? I will not yet touch your "why" statement. What is determining the "saturation level"? Is it just an inherent property of the vaccuum? What is taking on a saturation value? The E and B fields? you seem to say it is the point in space.
I only mentioned a meter to be sure you were considering fact that photon do have length and in some sense a long thin aspect ratio.
Dale has already objected to idea that a single photon has a single wavelength (or energy) and he is correct. - see my comment in the other post about conection to both Fourrier analysis and the uncertainity principle.
I do not feel we are making much progress in geting me to undersatand what you are saying, lets go a little slower - Is "flux" a "plane" as you state above? If so which, the E or B field oscillation plane or both which is not really a plane? Perhaps I do not need to understand or speak of "flux" but "center of the photon" and "a point ahead of it" seem to be very central to you idea so I need to have some idea what they are and how they are defined even if they can never be measured or observed.
I still have very little understanding of the "center of the photon" at times you call it a "point" and above it seems to be the line of the path. Is it a 0 D or 1 D object?
you are on very slipper ground if you think there is a difference. don't misunderstand- Certainly often we are ignorant of what is real due to measurment limitations - I am making a comment about the lack of any difference between what is real and what, in priciple, is knowable. I.e if in principle it is unknowable, then it is not real.
Billy T; thinks for taking time to think about this. I'm trying to describe a point in space where electric and magnetic fields are saturated; they can't get any stronger; it is the maximum possible. If this were not so, e = hv would not describe the energy content of a photon. You would need another factor, amplitude. You don't need that because h is the amplitude, this maximum possible value I'm trying to describe.
But that amplitude can only exist at the peaks of the photon's wave cycles. Spacially away from the peaks it is less. These peaks move through space at the speed of light.
I always thought that uncertainty meant you couldn't predict with certainty. We can know with more certainty after the fact, can't we ??
Ok, I think I see now. You're getting the two static equations (Del dot E proportional to charge density and Del dot B = 0 because no magnetic monopoles) muddled with the dynamic equations, Del x E proportional to dB/dt and Del x B proportional to the sum of the real current density and e0*dE/dt. e0*dE/dt being the displacement current.
>> edit I'm using e0 to represent the permitivity constant.
That is fundamentally incorrect, even in macroscopic measurements. No measurement is infinitely precise, there is always some uncertainty even after you have performed a measurement.
Hi DaleSpam; yes I know that; I didn't mean to imply that you could know precisely, just more precisely after the fact.
The Heisenburg uncertainty principle is considered a fundamental part of nature, and not simply a technical limitation.
Hi; DaleSpam; thanks for hanging in there; I've been pretty well Heisenburged. I know the numbers work; and the principle is useful. But this all started with a photon consists of one wave length; I think it does; you say not possible because of the Heisenburg principle.
How many wavelengths does a photon consist of; some undertermined number that is only decided when it is observed ?? Please Register or Log in to view the hidden image!
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No, it is still an undetermined number even after it is observed.
So you're telling me that this photon that is a quantum of energy such that e = hv, has an undetermined v ??
A photon will have a discrete energy, and a discrete, finite speed, and a discrete momentum. We will not know precisely the energy or momentum unless it is measured (or inferred, i.e. electron transisitions from atomic 'orbitals' produce discrete energies).
No kidding. So, when an atom's electron jumps orbit and produces a photon, that one photon can whizz through space as, say, 3/8 of one wavelength? Or, as 1 17/18 of one wavelength? Or as 29 43/44 of one wavelength?
and it can't be measuredd without changing it. Agreed. I was inferring that a single photon exists at a single wave length Please Register or Log in to view the hidden image!
No, we will still not know precisely even after it is measured. Have any of you ever done a measurement of any kind?
There are two separate issues here. One is the fact that all measurements have some amount of uncertainty. The other is the fact that as you determine one quantity precisely there are other quantities that you simultaneously lose precision on. The classic example is time and frequency where if you want to know a frequency precisely then, by the Fourier transform, you must sample it forever.
Hi DaleSpam; yes,I agree with all of your last post; even understand it. Emanual Kant once responded to David Hume's dismissal of causality by saying
I would use a similar argument that if a photon exists, then it must exist at a certain wavelength even though we may never be certain what that wave length is.
If the photon is not exactly massless, then it does have a minimum energy, namely its mass. If the photon is massless (as theory says it is), then there is no minimum energy, again because of Lorentz invariance.
Whether or not the photon is massless, there's no upper limit on wavelength.
In fact, in the case of a massive particle, the (spatial) wavelength can be
exactly infinite, not just arbitrarily large. It's the inverse of the
wavelength (called the wave number) that's constrained to be finite.
That addresses the first issue, that all measurements have some uncertainty. But it does not address the second issue, that the precision of one quantity is inversely related to the precision of another quantity.
If you say that a photon is like some piece of spaghetti that has a finite length, L, then it can only act for a finite amount of time, t=L/c. If it only has a finite amount of time then it cannot have an infinitely precise frequency. This is not a question of our limited precision in measurement, it is a question of the relationship between time and frequency. It is fine for you to claim that a photon is monochromatic as long as you understand that implies that it is eternal and therefore infinitely long.
I don't know where you are getting zero and infinity for a monochromatic photon. Why does monochromatic imply an infinitely small piece of a spectrum. Why not a quantum piece of a spectrum Please Register or Log in to view the hidden image! A photon is a quantum of energy by definition.
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