Photon

[GutZ]

This is my last bit of effort in trying to conceptualize the everything in physics....I made this image to help illustrate what I am saying.

 

 

http://img219.imageshack.us/img219/7950/76374648.jpg

 

First box:

 

This is how I gather an EM wave is. Photons of different concentrations and intensity, and that the mathematical representation would be like the squggly thing I made. How close I am here.

 

Second box:

 

If a particle or lets say photon again has energy (I assume thats what a carrier does) is it sort of in the sense trapped (for lack of a better word) surrounding the photon, or is it within the photon.

 

Three box:

 

Let's say a photon is zooming near an electron...and say the electron is in an state where it can take the energy from the photon. Does the electron take the energy move to a higher state and the photon just keeps going on. As the photon goes on does it actually gain speed because it lost energy(it's relativistic mass)? Also I read somewhere that a photon can eject an electron out of it's "shell" how does that work?

 

Fourth box:

 

I am gather that fields are what give properties to particles so does a field operate independant of the particles or do they have a relationship. Like say a photon going through a field area that has a higher intensity (by whatever means) does the photon gain more energy, or say a photon with lots of energy does it affect the field in some way.

 

If I can understand visually these concepts than I have a better chance of understanding things. If I am totally wrong and you guys can't correct me....I am going to be very sad.

[swansont]

There is an inherent shortcoming (AFAIK) of trying to visualize how photons behave, since the visualizations always seem to be based on classical notions.

 

 

Interactions with electrons break down into cases: for bound electrons, whether you ionize the electron or not, and then there's the case of a free electron. Bound electron interaction is absorption (and re-emission in the case of scattering). If the photon energy is high enough, the electron will be freed (ionization). Free electrons can't absorb photons — they must scatter.

 

The photon doesn't change speed in any of this.

[swaha]

pls dont mind but if we really cant visualize something how can we explain? how do we know?

[swansont]

That where math and models come in.

[swaha]

how do we know the math & models are correct then?

[Klaynos]

how do we know the math & models are correct then?

 

They make predictions about reality and we then check these against reality.

[Bob_for_short]

pls dont mind but if we really cant visualize something how can we explain? how do we know?

 

You can visualize the photon wave as a classical wave but you have to keep in mind that it represents the probability amplitude, not the real amplitude. It belongs to many-many separate one-photon experiments or to one experiment with many-many photons, whatever. The main point is that the probability is meaningful for many events, not for one.

Edited July 21, 2009 by Bob_for_short

[GutZ]

So how do you guy retain the logic behind physics. How did physics makes sense to you swansont. Is there anyway I can force myself away from visualization because that seems to be my prevalent method to understanding things.

 

Do you think the math would make more sense to me? like if I were to see an interaction through an equation? You guys have no idea how badly I want to understand this all but it seems like I am going in circles.

 

I don't care if it takes me 20 years.

[swansont]

So how do you guy retain the logic behind physics. How did physics makes sense to you swansont. Is there anyway I can force myself away from visualization because that seems to be my prevalent method to understanding things.

 

Do you think the math would make more sense to me? like if I were to see an interaction through an equation? You guys have no idea how badly I want to understand this all but it seems like I am going in circles.

 

I don't care if it takes me 20 years.

 

At first, it didn't. QM was terribly confusing at first. Now it is only moderately confusing. Math certainly helps, because discussion by analogy always fails at some level. Then you have to chip away at the misconceptions that set in, because ultimately all models are wrong in some way.

 

But this is one aspect of science. You make a model and see how it works in predicting and explaining behavior, as Klaynos has already mentioned. The classical notions fail — so you replace them. You find out that saying "we don't know what happens here" is better than a model which is wrong. And, in fact, seems to be the way QM works.: we don't know what's happening to a quantum system when we aren't observing it. Light goes through both slits when we don't measure which path it took, even if it's a single quantum of energy, so the model of a photon as a baseball-like particle with a well-defined trajectory goes out the window. The only way to know where a photon is, is to make it interact somewhere.

 

All of this takes time to absorb and digest. Learning is a never-ending process.

[GutZ]

oooooohhh, I am an idiot. WOW I am an idiot...Thanks!

 

I'll start out reading classical physics and get a good understand of that first with all the math.

 

SO the models and such bring about the right answer, but the exact details of what goes on is not totally clear or possible to perceive? Is this a limitation of technology or QM itself, like HUP discussions we had? Could we ever view the quantum world without disturbing it? like we do with classical physics.

[swansont]

We disturb the classical world when we observe it, but the perturbation is not small enough to notice. A photon bouncing off f a car doesn't have the same effect as a photon bouncing off an atom or electron.

 

A good grounding in classical physics is important, because even though some details differ at the quantum level, the basic concepts are still there.