# Two slit photon energy

Emissive
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?

Staff Emeritus
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.

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.

Staff Emeritus
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.

MRBlizzard
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?

Staff Emeritus