Imagine observing the frequency of light which is directed to the center of a gravitational field such as a planet. According to the gravitational-blueshift-effect, the frequency increases while getting closer to the center. Is this progress continuous?

If so, how does that fit with the photoelectric effect, which says the energy of light is quantized?

If not, would that mean light skips the states of energy in between? How would that work? Would that mean either time or space or both are quantized as well?

Please comment whatever comes to your mind about that problem or tell me if I made a big mistake in my thoughts. Thank you very much.

1 hour ago, Quantus said:

Is this progress continuous?

Yes.

1 hour ago, Quantus said:

If so, how does that fit with the photoelectric effect, which says the energy of light is quantized?

That just says that a photon, a quantum of light, is indivisible. A given photon can have any frequency (ie energy) at all but when it interacts with something (eg absorbed by an atom) then all of that energy is absorbed. It can't be partly absorbed. So the photoelectric effect says that the photon must have exactly the energy required to raise the energy level of an electron: it can't be done with two photons with half the energy, or with a photon with the energy plus a bit.

It is a bit like a vending machine that says "exact money only; no change given."

11 minutes ago, Strange said:

That just says that a photon, a quantum of light, is indivisible. A given photon can have any frequency (ie energy) at all but when it interacts with something (eg absorbed by an atom) then all of that energy is absorbed. It can't be partly absorbed. So the photoelectric effect says that the photon must have exactly the energy required to raise the energy level of an electron: it can't be done with two photons with half the energy, or with a photon with the energy plus a bit.

It is a bit like a vending machine that says "exact money only; no change given."

Interesting!

So a photon can't heat and reflect, but either heats or reflects?

22 minutes ago, QuantumT said:

Interesting!

So a photon can't heat and reflect, but either heats or reflects?

That is a good summary.

3 hours ago, Strange said:

Yes.

That just says that a photon, a quantum of light, is indivisible. A given photon can have any frequency (ie energy) at all but when it interacts with something (eg absorbed by an atom) then all of that energy is absorbed. It can't be partly absorbed. So the photoelectric effect says that the photon must have exactly the energy required to raise the energy level of an electron: it can't be done with two photons with half the energy, or with a photon with the energy plus a bit.

It is a bit like a vending machine that says "exact money only; no change given."

This is exactly how the Pound-Rebka experiment showed its results. The gammas that normally could be emitted and absorbed readily would not be absorbed when the source and targets were at different gravitational potentials. The light had to be Doppler-shifted to match the frequencies.

(though two photons at half the energy does work, if angular momentum is conserved, and excitation isn’t the photoelectric effect)

29 minutes ago, swansont said:

(though two photons at half the energy does work, if angular momentum is conserved, and excitation isn’t the photoelectric effect)

As I wrote that, I did wonder ...

LOL you know more than you realize. I often try to double check my statements just in case I make  mistake, its one of the primary reasons why I often edit posts after my initial post.  

10 hours ago, swansont said:

(though two photons at half the energy does work, if angular momentum is conserved, and excitation isn’t the photoelectric effect)

This also highlights a second way in which I was wrong (or not completely accurate). In the case of the photoelectric effect, where the electron is expelled from the atom then the photon causing this can have more energy then just the energy to free the electron (the ionisation energy) because any extra energy will be converted to kinetic energy of the electron.

So the photoelectric vending machine does give change. But in the form of credit rather than a "smaller" photon.

Well I seriously doubt total accuracy in any analogy is ever possible lol. However in any scattering event the mass energy conservation applies. This includes the invariant (rest mass) and particle momentum terms. Total mass/energy in = total mass/energy out. This conservation law as well as those others such as charge conservation, flavor, lepton, isospin etc  is what determines what possible particle decays can occur. 

Edited January 19, 20197 yr by Mordred