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anantchowdhary
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I am very new to quantum physics.Now i would like to know how a photon moves.
Is it in a straight line,or is it in a wave like pattern?
Is it in a straight line,or is it in a wave like pattern?
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anantchowdhary said:I am very new to quantum physics.Now i would like to know how a photon moves.
Is it in a straight line,or is it in a wave like pattern?
How timely. I too am re-reading Feynman's QED book that you mention. I was just going to start a new thread to ask a question about the path integral for photons when I caught this post. Thanks.marlberg said:According to R.P. Feynman Photons have a probability amplitude to move from a source to a detector. It appears to move in a straight line only because that is where the Highest Area of probability for the amplitude of an event is. Interestingly enough for any given photon moving between Source A and Detector B in order to calculate the Probability Amplitude correctly you must determine how many ways there are for a Photon to get from A to B. Most of the "paths" that a photon may take from Source A to Detector B are very small percentages of probability and each of those paths can and must have an opposite path so that if we define a path from A to C to B then there must be a path from A to -C to B and of course these paths cancel each other out it is only in the area of least energy where the paths become "straighter" that the Probability Amplitudes begin to reinforce rather than cancel i.e. where there is less "turning of the arrows", see QED the strange theory of light and matter for a full discussion of this, and thus photons have a "tendency" to travel in linear directions it is only the Area of the Probability Amplitude for an event that gives a wave like motion to a photon.
Btw I am on my 5th reread of QED and I still have trouble with much of it :uhh:
So I may have buggered this response up quite badly so those with more learning and knowledge please feel free to correct me
hth
Mike2 said:How timely. I too am re-reading Feynman's QED book that you mention. I was just going to start a new thread to ask a question about the path integral for photons when I caught this post. Thanks.
Does the path integral for a photon also include paths that go backwards in time from detector to source.
marlberg said:Not in Feynmans work. There may be such a treatment in others but the photon (and electron) as treated in Feynmans work is a "spin 0" particle. It is and Ideal particle and not a "real" particle. For his treatment of a "real" electron/photon he terms the particle electron as a spin 1/2 with a coupling j of -1 and the photon as a spin 1/2 with no j component.
Mike2 said:Just found it: on page 98,
"Every particle in Nature has an amplitude to move backwards in time, and therefore has an anti-particle... Photons look exactly the same in all respects when they travel backwards in time - as we saw earlier - so they are their own anti-particle."
So my next question would be is there a path backwards in time corresponding to every path forwards in time? thanks.
Quantum physics explains that photons, which are particles of light, move in a wave-like manner. This means that they have both particle and wave properties, and their movement can be described by a mathematical equation known as the Schrödinger equation.
In quantum physics, the Heisenberg uncertainty principle states that it is impossible to know the exact position and momentum of a particle, such as a photon, at the same time. This means that the movement of photons is inherently uncertain, and can only be described in terms of probabilities.
In quantum physics, photons interact with matter through a process called absorption and emission. When a photon is absorbed by an atom, it transfers its energy to the atom, causing an electron to move to a higher energy level. When the electron returns to its original energy level, it emits a photon of the same energy.
Yes, in quantum physics, photons are massless particles that can travel at the speed of light in a vacuum. This is because they do not experience the effects of time or space, and can only be described in terms of their energy and momentum.
In quantum physics, entanglement is a phenomenon where two or more particles become connected in such a way that the state of one particle affects the state of the other, regardless of the distance between them. This means that the movement of photons can be influenced by the entanglement of other particles, even if they are separated by vast distances.