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phillip256

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El Hombre Invisible

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You're talking about 'photons', so I assume you're referring to the quantum theory, not classical EM theory, of light. Note, then, that the photon doesn't interfere with itself (unlike in EM). It is the wavefunction, i.e. the probability waves of the two trajectories, that interfere with themselves. At any position between the emitter and the detector you have a probability of finding the photon for each path (left slit or right slit). This probability can be zero, since the the probability is given by the square of the sums of the wavefunctions, and the wavefunctions may be negative (so 0.5 + -0.5 squared is zero). It's not a case of "needing" multiple crests - multiple crests are a consequence of having a photon that may be anywhere between the emitter and detector.

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jtbell

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BigMacnFries said:how many wave crests does a photon have?

You're apparently thinking of a photon as a little bundle or pulse of waves, a "wave packet". Don't do that! The wave associated with a photon extends over a large region of space, and is related to the probability of finding the photon at any particular location.

I think the size of the region that the wave function covers has little or nothing to do with the size of the photon itself, but has more to do with the conditions under which the photon is produced. If your setup contains a light source that is "on" continuously, but whose intensity is reduced enough so that it produces photons at random, say once every second on the average, then the wave function fills the entire volume of space that is illuminated by the light source (regardless of intensity). If your light source has a shutter that opens for a very short time, then the wave function covers a smaller volume of space, corresponding to the length of time that the shutter is open.

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El Hombre Invisible

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Yes, a photon is emitted when an electron makes a transition from a higher energy level to a lower one. Free electrons are known to radiate when they deccelerate. Since this requires a change in kinetic energy, there is no inertial frame in which photon emission would violate energy conservation.BigMacnFries said:

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jtbell

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