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a problem regarding interference.


swaha
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i was reading quantum mechanics by dirac where i found he proposed that the same photon has equal probability to stay in two interfering beams simultaneously. i didnt get what is the difference in supposing the other way which is simpler that half of the photons are in 1 beam the other half in other beam.

the proposition was regarding 1 photon so statistically the probability remains same.

besides this idea was avoided in polarization case. why? where no new theory was required to be proposed. please explain.

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There is no such a thing as a half of photon. Photon carries energy, and a half of energy is not observed. Dirac states the experimental facts.

 

The first mentioning that I know about interference of a photon with itself was made by H. Poincaré in his "Last Thoughts" (1913), as a logical consequence of a quantum nature of light and low intensity regime of interference.

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i didnt understand. how can the photon interfere with itself? half a photon i didnt say what i meant was half the no of photons are in one beam the other half in the other beam.

suppose u have water in a large pipe & want to distribute it in two equal pipes. half the no of molecules go in one pipe other half to the other. y this isnt true regarding photon particles???

pls explain.

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Photon is not a particle, it is a wave. For a wave to propagate it is important to take correctly into account all obstacles (double- or multiple slit screen).

 

The interference pattern is obtained as result of many photon hits. The notion of probability belongs to the whole set of hits. The wave function, as a probability amplitude, belongs to the whole set too, not to one hit.

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i didnt understand. how can the photon interfere with itself? half a photon i didnt say what i meant was half the no of photons are in one beam the other half in the other beam.

suppose u have water in a large pipe & want to distribute it in two equal pipes. half the no of molecules go in one pipe other half to the other. y this isnt true regarding photon particles???

pls explain.

 

You are drawing a classical analogy here, and this behavior isn't classical. As Bob has stated, it's still a wave, even though the energy is quantized.

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Light is a wave, but unlike classical waves, it has certain behavior like being localized when it interacts and having quantized energy. We associate those properties with particles, so we call a photon a particle. But it never stops being a wave — it's just that it doesn't act like a classical wave.

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how can u say light has quantized energy?

what is localized light? i think it never stops.


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even if light is quantised being a wave how can a photon interfere with itself? if it has to do so it must be present in both the beams simultaneously. bt how can 1 thing be at 2 different palces at the same time?

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how can u say light has quantized energy?

what is localized light? i think it never stops.

 

Light is observed to behave this way. Even though it's a wave, when it interacts it is observed to have discrete amounts of energy, which it deposits in a localized area (e.g. an atom)

 

even if light is quantised being a wave how can a photon interfere with itself? if it has to do so it must be present in both the beams simultaneously. bt how can 1 thing be at 2 different palces at the same time?

 

Welcome to the world of quantum mechanics. It turns out that trajectories are not well-defined on this scale (unlike the classical world we're used to), so the light travels both paths.

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ok. what if we dont allow them to interfere instead let them fall on two different points so that we may observe the pts. now how can the same light make two things visible at different places at the same time? does it mean if light diverges from a pt all photons it carried do travel simultaneously in all beams? what's wrong in supposing half of the photons in one beam & the other half in other beam? after all the intensity does reduce the same way. it wasnt clear sir. please explain & send me the links, name of books what i should study regarding this.

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Any QM textbook will discuss the basics of this.

 

You get the interference pattern even if only one photon at a time is in the apparatus. If you restrict the path by blocking one of the slits, you won't get interference.

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