# Two slit photon energy

by Emissive
Tags: energy, photon, slit
 P: 20 If we perform the two slit experiment vertically - so the slots are above one another - we should observe a small amount of red / blue shift in the energy of the photons when they hit the screen (due to gravity). The path length from each slit is not symetric so the arriving photons energy would vary depending on the route. This would avoid measuring the photons at the slits but still - over time - assuming the equipment was sensitive enough - predict which path a photon took. Would the arriving energy level of the photon be a combination of the energies of a photon going through both the two slits path? Or always be one of the two energy levels required for it go down either path?
 Mentor P: 11,574 The energy loss from a photon is the same no matter which slit it went through. All you would know is that the photons hitting the upper part of the sensor are redshifted a little bit more than the lower part, not which path they took.
 P: 8 How about single photon interference with the backstop an photoelectron material. If the electron comes through the top slit and down to a central, phase additive line, then an electron is emitted. Otherwise, through the bottom slit, the energy is insufficient. Personally, I'm not sure that you can get an narrow enough bandwidth to detect the tiny, tiny energy difference.
Mentor
P: 11,574
Two slit photon energy

 Quote by MRBlizzard How about single photon interference with the backstop an photoelectron material. If the electron comes through the top slit and down to a central, phase additive line, then an electron is emitted. Otherwise, through the bottom slit, the energy is insufficient. Personally, I'm not sure that you can get an narrow enough bandwidth to detect the tiny, tiny energy difference.
You're missing the point of the experiment. He's proposing that you can detect which slit the photon went through by measuring its energy upon detection. But this won't work. A photon detected 1 inch above the center of the screen will have an identical amount of energy no matter which slit it came through. It's not path length that matters, it's net vertical movement in the gravitational field, and that remains the same no matter which slit it goes through.
 P: 8 it's net vertical movement in the gravitational field, and that remains the same no matter which slit it goes through. Why doesn't the photon passing through the higher slit gain energy upon descending to the middle of the screen, where the interference occurs?
Mentor
P: 11,574
 Quote by MRBlizzard Why doesn't the photon passing through the higher slit gain energy upon descending to the middle of the screen, where the interference occurs?
Who said it doesn't?
But first it must lose energy because it passed through the top slit, so the gain is equal to the loss. And the reverse is true for one passing through the bottom. First it gains energy, then it loses it. So whether it passes through the bottom or the top the energy is the same.

 Related Discussions Quantum Physics 1 Quantum Physics 5 Quantum Physics 2 Quantum Physics 0 Quantum Physics 15