What is an X ray photon?

Wryel · 21 May 2006 at 17:56

I had an A-level question that asked if the surface something landed onto would affect its impact velocity, they put them in to ensure you aren't just roboticaly answering the questions without actually understanding them.

SoSolid · 21 May 2006 at 18:06

Hey, sorry. Well the original question (upon correctly reading it this time

) Simply asks to write down the speed of an x ray photon lol which does seem awfully easy to me. Of course it would just be the speed of light as you all said wouldn't it? Oh well i'm not complaining, easy marks?

Socaddict · 21 May 2006 at 18:08

yep, easy marks. sounds like a past paper that I did.

SoSolid · 21 May 2006 at 18:09

The question after that is to then "calculate" the wavelength, So yeh, as one poster said I guess they are just making sure you don't robotically answer queations.

Psyk · 21 May 2006 at 18:31

This is probably out of the scope of A-level but does a photon actually have a speed? Light travels at c but really light is a wave that determines the likelihood of a photon being present at any given point. So going by that definition, the photon itself is either there or it's not. It's not a particle that actually travels at c.

daz · 21 May 2006 at 18:36

Psyk said:
This is probably out of the scope of A-level but does a photon actually have a speed? Light travels at c but really light is a wave that determines the likelihood of a photon being present at any given point. So going by that definition, the photon itself is either there or it's not. It's not a particle that actually travels at c.

It is a particle and a wave, depending on the experiments you perform on it. The photoelectric effect = particle etc.

Psyk · 21 May 2006 at 18:43

daz said:
It is a particle and a wave, depending on the experiments you perform on it. The photoelectric effect = particle etc.

Aye I know that, but I'm thinking deeper than how it's described in A-level. What I mean is I don't think of a photon as a particle that is flying through space at exactly 3x10^8m/s, merely one that is just there or it isn't.

JonC · 21 May 2006 at 19:21

Psyk said:
Aye I know that, but I'm thinking deeper than how it's described in A-level. What I mean is I don't think of a photon as a particle that is flying through space at exactly 3x10^8m/s, merely one that is just there or it isn't.

Well yes, so is an electron, a car, a house. They are all either there or not.

Yes a photon can be described by a wave, as can any particle. It's speed being the speed of movement of the position of the most likely ocurrance of the particle (the peak of the wave). When we start getting into interference everything gets a bit screwy....

But in this case 3x10^8 will probably do.

jonc

Psyk · 21 May 2006 at 20:37

JonC said:
Well yes, so is an electron, a car, a house. They are all either there or not.

Yes a photon can be described by a wave, as can any particle. It's speed being the speed of movement of the position of the most likely ocurrance of the particle (the peak of the wave). When we start getting into interference everything gets a bit screwy....

But in this case 3x10^8 will probably do.

jonc

Ok that makes sense. So I suppose it does make sense for the speed of a photon to be c.

SoSolid · 21 May 2006 at 21:11

I understand how particles behave like waves but do waves behave like particles such as in the photoelectric effect? Would this be a good example to use if questioned on it, for example that the photons above a certain "threshold" frequency supply the electrons with enough energy inorder to be emitted from the metal.

JonC · 21 May 2006 at 21:16

SoSolid said:
I understand how particles behave like waves but do waves behave like particles such as in the photoelectric effect? Would this be a good example to use if questioned on it, for example that the photons above a certain "threshold" frequency supply the electrons with enough energy inorder to be emitted from the metal.

Well considering how Einstein used this as one of his examples to argue for wave/particle duality, I would think it would be the perfect example.

jonc

Pickers · 22 May 2006 at 08:21

daz said:
I know it has no bearing on the resultant photon. However, what we define as X-rays and gamma rays overlap, the only difference being the method of creation.

How it is generated has no bearing on its title. The grey area is really from energies in the 10s of keV up to a couple of hundred, and its at the discretion of the analyser/reader as to how to interpret it.
I go by
0.1-2 or 3 keV = soft X-ray
2 or 3 to 30 = hard x-ray
50+ = Gamma-ray

But it all depends on the energy band. For example my project was looking at photon energies from 0.1 - 200 keV, so for such a broad range, I drew my boundaries accordingly.