[Petrochemicals (OP)]

When a photon is ejected from an electron going to a lower energy level, what acceleration does the photon have?

[geordief]

When a photon is ejected from an electron going to a lower energy level, what acceleration does the photon have?

From what I have read  a photon (in a vacuum) does not accelerate and only moves at the one speed(c)

[alancalverd]

It doesn't matter. As the photon has no mass you can either consider it to be "born" at c, or to accelerate instantaneously. This just shows the confusion that can arise from taking mathematical models to be real things.

[Petrochemicals (OP)]

When a photon is ejected from an electron going to a lower energy level, what acceleration does the photon have?

From what I have read  a photon (in a vacuum) does not accelerate and only moves at the one speed(c)

As it transitions between mediums?

[Petrochemicals (OP)]

It doesn't matter. As the photon has no mass you can either consider it to be "born" at c, or to accelerate instantaneously. This just shows the confusion that can arise from taking mathematical models to be real things.

Is this another to chalk up to quantum effects, relativity etc? Effectivley we don't really know?

[Eternal Student]

Hi.

When a photon is ejected from an electron going to a lower energy level, what acceleration does the photon have?

   It's not necessarily the electron that is ejecting it.   The entire atom plays a part.   The energy levels you are speaking of exist only because the electron is part of a system.
   In any inertial frame you choose to use, the photon is always moving at speed c.   There is never any change from a lower speed to a higher speed or vice versa.   The only meaningful acceleration you could assign to the photon is 0 at all times.
    (You could use an accelerated frame but that's not sensible and not worth discussing).

     I'm going to guess that you are imagining the photon as something that was hiding inside the electron and had to be pushed out or accelerated.   Don't do that - it's not a great model or image to have.  The photon wasn't inside the electron and it was never at rest.  It just appeared and was always moving at speed c from the moment of creation.   That doesn't do much to explain why or how some things (like a photon) can just appear.   It's just a useable model which transfers the mystery from one place to another, you just do accept that a photon can suddenly appear.
     A more complete model might use QFT but that's probably not worth discussing here.   

Best Wishes.

[Bored chemist]

It's always dodgy to talk about " a photon's point of view" but, since they travel at C, time dilation means that time stops.
If time doesn't exist, it's a bit tricky to differentiate position wrt it twice.

What's the acceleration of a water wave?

[geordief]

When a photon is ejected from an electron going to a lower energy level, what acceleration does the photon have?

From what I have read  a photon (in a vacuum) does not accelerate and only moves at the one speed(c)

As it transitions between mediums?

I will defer to others here to answer that .....

[Eternal Student]

Hi.

I completely missed the bit about transitions to different mediums, well spotted @geordief .

Here's a pleasant Physics expert talking about why or how light slows down in glass for a YouTube video produced by Sixty Symbols,  it lasts about 15 minutes  and you might as well listen to him rather than read some waffle I produce.

So here's 4 different answers, which are are more or less bullet points summarising that video as I saw it:

 1.   Light can travel more slowly in different mediums but photons don't.   Don't ask, live with it. 
Be aware that many of the old and popular explanations are wrong.

 2.   A photon is a particle that is only readily identified in a vaccum.   Inside a dense medium which is some regular lattice structure of atoms, what you will actually have is a different particle (sometimes called a quasiparticle) which is known as a "polariton".   These polaritons travel at less than the speed of light.
     So the photon wasn't accelerated or ever travelling at less than the speed c,   instead it was just changed into a polariton once inside the dense medium.

  3.  The photon is a quantum mechanical object.   It can take all possible paths through the medium and some of those involve an interaction with other QM objects like electrons and nucleons that are present in the dense medium.  The sum of all the possible paths is such that the overall wave description looks like a photon that has been delayed (travelling at less than c).
     There are similarities between the Quantum Mechanical model and the explanation using classical electromagnetic waves.  With the classical model, an e-m wave passing close to an atom will cause charged particles like the electrons of the atom to oscillate.  However, oscillating electrons will produce their own electromagnetic waves.   So these will interfere with the main wave that was passing through.   (For the QM model, we have that one photon takes mutiple paths so it is all the wave you need on its own and also the interactions with electrons are "like" the classical interaction in some broad sense).

4.   I'm not actually certain I can really articulate a 4th answer.   I'm just fairly sure you could find one if you tried.

Best Wishes.

[alancalverd]

Never a good idea to fixate on a photon as a particle nor electromagnetic radiation as a wave. These are not "things" but convenient models of what happens.

When an electron (definitely a thing - it has mass) accelerates, electromagnetic energy has to come from or go to somewhere. If the acceleration is a change in quantum state, the energy will be quantised.