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is light a probability wave?


gib65
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1) I know that light exhibits wave/particle duality.

 

2) I know that pretty much all fundamental particles exhibit the same kind of duality where the "wave" is a region of probability where the particle might exist.

 

Conclusion: the "wave" property of light is the same region of probability for the photon.

 

Not exactly a deductive argument, but am I right?

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I think this also puts the focus on the importance of the question asked.

 

The answer you get (to anything) is often seriously constrained by the construction of your question. More often than not, I've found that confusion arise simply because it's easy to forget that alot of responsibility is on formulating the questions.

 

In a certain sense, wave particle duality can be thought of different ways of asking the questions. This is also shows that "what is reality" really does depend on what sort of answer we are looking for - what do we "want" it to be? What sort of answer do we want? We apparently to not prefer answers in terms of completely non-causal models, even though that technically might be possible. We are looking for whatever it is, some kind of "natural" answers... typically in terms of cause and effect. To what extent such answers exists within a finite model is not a priori obivous. This is why I think that a good model must be adaptive in a natural way. But this is just my opinion.

 

To understand this uncertainty concept one can easily see that this phenomenon isn't specific to quantum mechanics. In any field, the way you ask question does influence the set of possible answers you get. In this respect this is nothing magic so to speak. I think that "reality" in the absolute sense is pretty much an illusion, and it is rather a creation, and I think not a unique one.

 

At first one may think that this insight would be depressing and imply that we don't stand much of a chance of accomplish much of value. But I think of it in another way, this insight provides also the key to improvement and releases us from some mental blockings.

 

/Fredrik

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  • 4 weeks later...
I think this also puts the focus on the importance of the question asked.

 

The answer you get (to anything) is often seriously constrained by the construction of your question. More often than not, I've found that confusion arise simply because it's easy to forget that alot of responsibility is on formulating the questions.

 

In a certain sense, wave particle duality can be thought of different ways of asking the questions. This is also shows that "what is reality" really does depend on what sort of answer we are looking for - what do we "want" it to be? What sort of answer do we want? We apparently to not prefer answers in terms of completely non-causal models, even though that technically might be possible. We are looking for whatever it is, some kind of "natural" answers... typically in terms of cause and effect. To what extent such answers exists within a finite model is not a priori obivous. This is why I think that a good model must be adaptive in a natural way. But this is just my opinion.

 

To understand this uncertainty concept one can easily see that this phenomenon isn't specific to quantum mechanics. In any field, the way you ask question does influence the set of possible answers you get. In this respect this is nothing magic so to speak. I think that "reality" in the absolute sense is pretty much an illusion, and it is rather a creation, and I think not a unique one.

 

At first one may think that this insight would be depressing and imply that we don't stand much of a chance of accomplish much of value. But I think of it in another way, this insight provides also the key to improvement and releases us from some mental blockings.

 

/Fredrik

 

nice post Fredrik.

 

I heard, that normal, even coherent, light is the state where number of photons is undefined. So it is impossible to treat light as probability of photon presence as we treat it with electron.

But, doesn't light behave the same way whether there an undefined number of photons or just one? The double slit experiment shows that.

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  • 3 years later...

Yes light is a probability wave, essentially moving potential energy.

Wave quanta from a source radiate forming shells of thickness equal to the quantum vibration length

(medium dependant). The shell can be described as a probability wave (pw) for interaction.

Interaction evokes a non local action. The probability wave collapses (resets to zero) for all locations

referred to that quantum. This is to conserve energy.

Also at interaction, all the quantum energy is converted to other energy, possibly including lower energy pw’s.This happens at a single quantum location.

 

Probability waves comprise free photons, gravitons and moving mass. They move at velocity c. They exhibit

wave effects, but show different interaction properties.All are subject to non local wave collapse at interaction.

Free photons convert energy only at the interaction location.

When gravitons interact with mass, energy is converted both at source and interaction location.

An additional non local effect is instant + vector gravity force referred to the CURRENT (ie universal)

interaction time locations of source and interaction.

Edited by galen
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We must not get confused between the particle wave of photons and the wave nature of light. The existance probability of photons gets applied on the emission of photons by the light source (charge or current), after that the photons are well distributed according to the emission probability density, and the electric and magnetic fields are defined.

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  • 3 weeks later...
Damn good question actualy! :)

 

I know electrons take every possible path from A to B, the Photon may do this also, although it makes me wonder about Lasers and coherence.

 

I'm going to have to disagree.

 

I don't believe electrons take every possible path (I would like to know where you heard that from or why you know this), though they have the ability to take certain paths and based on its wave function you can find the probability of where it will be, but it does have a definite location.

 

The wave function (or its probability wave) is not the actual wave-like property of light or matter. The wave function is merely a mathematical model of what you are describing, in the case of an electron, its usually position, but can also be spin or something of the like. Depending on how you construct the hamiltonian (energy of the system) of Schroedinger's equation is what determines the physical entity you are describing.

 

So as far as I know: No light is not a probability wave, because the probability wave is not something physical, but a description of something physical.

 

Edit: Also, anything can have a probability wave if you want it to.

 

lol how did this one get get pulled out of the stack, just realized this is from 2007, gah I dislike posting on old stuff.

Edited by darkenlighten
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I'm going to have to disagree.

 

I don't believe electrons take every possible path (I would like to know where you heard that from or why you know this), though they have the ability to take certain paths and based on its wave function you can find the probability of where it will be, but it does have a definite location.

 

The wave function (or its probability wave) is not the actual wave-like property of light or matter. The wave function is merely a mathematical model of what you are describing, in the case of an electron, its usually position, but can also be spin or something of the like. Depending on how you construct the hamiltonian (energy of the system) of Schroedinger's equation is what determines the physical entity you are describing.

 

So as far as I know: No light is not a probability wave, because the probability wave is not something physical, but a description of something physical.

 

Edit: Also, anything can have a probability wave if you want it to.

 

lol how did this one get get pulled out of the stack, just realized this is from 2007, gah I dislike posting on old stuff.

 

Have you ever heard of the double slit experiment?

 

 

That video may seem juvenile but it is accurate.

 

Also I think Richard Feynman was the one responsible for the Sum over histories. Every system takes every possible path (or history) from A to B. You might also want to look up superposition.

 

http://en.wikipedia.org/wiki/Path_integral_formulation

 

In physics and chemistry, wave–particle duality is the concept that all energy (and thus all matter) exhibits both wave-like and particle-like properties. Being a central concept of quantum mechanics, this duality addresses the inadequacy of classical concepts like "particle" and "wave" in fully describing the behavior of quantum-scale objects. Orthodox interpretations of quantum mechanics explain this ostensible paradox as a fundamental property of the Universe, while alternative interpretations explain the duality as an emergent, second-order consequence of various limitations of the observer. This treatment focuses on explaining the behavior from the perspective of the widely used Copenhagen interpretation, in which wave–particle duality is one aspect of the concept of complementarity, that a phenomenon can be viewed in one way or in another, but not both simultaneously.

 

http://en.wikipedia.org/wiki/Wave%E2%80%93particle_duality

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Um I don't know if you misunderstand. I'm pretty sure a system does not physically take every possible path, but it is described by the superposition of all possible states.

 

Particles behave like waves until observed or measured, so yes at some level it does physically take place. Again I reference the double slit experiment.

 

There is a variation of the double-slit experiment in which detectors are placed in either or both of the two slits in an attempt to determine which slit the photon passes through on its way to the screen. Placing a detector even in just one of the slits will result in the disappearance of the interference pattern. The detection of a photon involves a physical interaction between the photon and the detector of the sort that physically changes the detector. (If nothing changed in the detector, it would not detect anything.) If two photons of the same frequency were emitted at the same time they would be coherent. If they went through two unobstructed slits then they would remain coherent and arriving at the screen at the same time but laterally displaced from each other they would exhibit interference. However, if one or both of them were to encounter a detector, time could be required for each to interact with its detector and they would most likely fall out of step with each other—that is, they would decohere. They would then arrive at the screen at slightly different times and could not interfere because the first to arrive would have already interacted with the screen before the second got there. If only one photon is involved, it must be detected at one or the other detector, and its continued path goes forward only from the slit where it was detected.[9]

 

From there you can go by the different interpretations. A widely accepted one is the Copenhagen Interpretation.

 

The probability "wave" can be said to "pass through space" because the probability values that one can compute from its mathematical representation are dependent on time. One cannot speak of the location of any particle such as photon between the time it is emitted and the time it is detected simply because in order to say that something is located somewhere at a certain time one has to detect it (of course, since photons travel at a known speed (the speed of light) at any given time (stated to Planck accuracy) you can calculate (to within Planck distance) where the 'probability' field is 'centered', but until the particle is detected, you can not be certain 'exactly' where it is).

 

http://en.wikipedia.org/wiki/Double-slit_experiment

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I'm very well aware of the double split experiment. Saying they take every path possible seems over the top to me, but nonetheless, to the original question, light is not a probability wave.

 

But light is a probability wave until it interacts with an observer, that is what collapses the wave function, that is the whole point of the double-slit experiment.

 

In physics and chemistry, wave–particle duality is the concept that all energy (and thus all matter) exhibits both wave-like and particle-like properties.

 

http://en.wikipedia.org/wiki/Wave%E2%80%93particle_duality

 

Strictly speaking, the term particle is a misnomer because the dynamics of particle physics are governed by quantum mechanics. As such, they exhibit wave-particle duality, displaying particle-like behavior under certain experimental conditions and wave-like behavior in others (more technically they are described by state vectors in a Hilbert space; see quantum field theory). Following the convention of particle physicists, "elementary particles" refer to objects such as electrons and photons, it is well known that these "particles" display wave-like properties as well.

 

http://en.wikipedia.org/wiki/Particle_physics

 

Photons, like all quantum objects, exhibit both wave-like and particle-like properties. Their dual wave–particle nature can be difficult to visualize. The photon displays clearly wave-like phenomena such as diffraction and interference on the length scale of its wavelength. For example, a single photon passing through a double-slit experiment lands on the screen exhibiting interference phenomena but only if no measure was made on the actual slit being run across. To account for the particle interpretation that phenomena is called probability distribution but behaves according to the Maxwell's equations.[47] However, experiments confirm that the photon is not a short pulse of electromagnetic radiation; it does not spread out as it propagates, nor does it divide when it encounters a beam splitter"[48]. Rather, the photon seems to be a point-like particle since it is absorbed or emitted as a whole by arbitrarily small systems, systems much smaller than its wavelength, such as an atomic nucleus (≈10−15 m across) or even the point-like electron. Nevertheless, the photon is not a point-like particle whose trajectory is shaped probabilistically by the electromagnetic field, as conceived by Einstein and others; that hypothesis was also refuted by the photon-correlation experiments cited above. According to our present understanding, the electromagnetic field itself is produced by photons, which in turn result from a local gauge symmetry and the laws of quantum field theory (see the Second quantization and Gauge boson sections below).

 

http://en.wikipedia.org/wiki/Photon#Wave.E2.80.93particle_duality_and_uncertainty_principles

 

So light can be described as a wave, but at times can also be described as a particle, to simply say that light cannot a wave is not accurate. Especially if you point out from above,

 

To account for the particle interpretation that phenomena is called probability distribution but behaves according to the Maxwell's equations.
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Okay yea so you do not know what a probability wave is. Of course light acts like a wave and a particle, that is known. The probability wave is not the description of the physical wave-like nature.

 

I think people get confused when one talks about the wave function and a probability wave. The wave function describes a physical system, which doesn't have to be necessarily the position of a particle. A probability wave is the mathematical description of the probability of that system doing a certain thing, such as an electron's position.

 

So no light is not a probability wave, nothing is a probability wave. Unless I'm skewing what you and the poster mean by a probability wave. Because as far as I know it, it is the wave function squared or [math] |\Psi|^2 [/math]

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Okay yea so you do not know what a probability wave is. Of course light acts like a wave and a particle, that is known. The probability wave is not the description of the physical wave-like nature.

 

I think people get confused when one talks about the wave function and a probability wave. The wave function describes a physical system, which doesn't have to be necessarily the position of a particle. A probability wave is the mathematical description of the probability of that system doing a certain thing, such as an electron's position.

 

So no light is not a probability wave, nothing is a probability wave. Unless I'm skewing what you and the poster mean by a probability wave. Because as far as I know it, it is the wave function squared or [math] |\Psi|^2 [/math]

 

Light can be measured as quanta, or wave packets of light.

 

In physics, a wave packet is a short "burst" or "envelope" of wave action that travels as a unit. A wave packet can be analyzed into, or can be synthesized from, an infinite set of component sinusoidal waves of different wavenumbers, with phases and amplitudes such that they interfere constructively only over a small region of space, and destructively elsewhere.[1] Depending on the evolution equation, the wave packet's envelope may remain constant (no dispersion, see figure) or it may change (dispersion) while propagating. Quantum mechanics ascribes a special significance to the wave packet: it is interpreted to be a "probability wave" describing the probability that a particle or particles in a particular state will be measured to have a given position and momentum. It is in this way similar to the wave function.

 

http://en.wikipedia.org/wiki/Wave_packet

 

Furthermore, how can you imply that the probability wave of a set photon is not an accurate description of the photon in reality. Essentially the math is based off of all observable evidence pertaining to photons.

 

A wave function or wavefunction is a mathematical tool used in quantum mechanics to describe the momentary states of subatomic particles. It is a function from a space that maps the possible states of the system into the complex numbers. The laws of quantum mechanics (i.e. the Schrödinger equation) describe how the wave function evolves over time. The values of the wave function are probability amplitudes — complex numbers — the squares of the absolute values of which give the probability distribution that the system will be in any of the possible states.

 

It is commonly applied as a property of particles relating to their wave-particle duality, where it is denoted ψ(position,time) and where | ψ | squared is equal to the chance of finding the subject at a certain time and position.[1] For example, in an atom with a single electron, such as hydrogen or ionized helium, the wave function of the electron provides a complete description of how the electron behaves. It can be decomposed into a series of atomic orbitals which form a basis for the possible wave functions. For atoms with more than one electron (or any system with multiple particles), the underlying space is the possible configurations of all the electrons and the wave function describes the probabilities of those configurations.

 

So at this point you can either concede your point, that the physical description of light cannot be described by a probability wave, or you simply aren't looking at the facts.

Edited by toastywombel
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So you are not reading what I am writing. The wave function is the physical description of the wave, but the probability wave is the probability of it being at a certain place.

 

Have you taken a Quantum Mechanics class yet?

 

Whether I have taken a Quantum Mechanics class is not the point. The physical description of the wave is the wave function.

 

The values of the wave function are probability amplitudes, and with the wave function you get the probability distribution. How is a wave function not a probability wave?

 

Again,

 

wave packet: it is interpreted to be a "probability wave" describing the probability that a particle or particles in a particular state will be measured to have a given position and momentum. It is in this way similar to the wave function.

 

http://en.wikipedia.org/wiki/Wave_packet


Merged post follows:

Consecutive posts merged

Now you seem to be changing the point on semantics, you originally said this though and that was what was dead wrong,

 

I don't believe electrons take every possible path (I would like to know where you heard that from or why you know this), though they have the ability to take certain paths and based on its wave function you can find the probability of where it will be, but it does have a definite location.

 

The reason it does not have a definite location is because it has a probable location in all possible paths from A to B.

 

In order to find the overall probability amplitude for a given process, then, one adds up, or integrates, the amplitude of postulate 3 over the space of all possible histories of the system in between the initial and final states, including histories that are absurd by classical standards.

 

http://en.wikipedia.org/wiki/Path_integral_formulation

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