How to apply e=mc^2 to a photon?

[Hootenanny]

I'll try and paraphrase what Zz posted in order to make it easier to understand. Solids are made up of a network of ions (charged particles, in this case atoms) and electrons. Imagine that the atoms are balls, evenly spaced forming a cubic lattice, with springs connecting one atom to the next something like http://www.teachmetuition.co.uk/Chemistry/Chemicalstructureandbonding/cubeionstotal.gif" . These lattices have vibrational energy levels, similar to the energy levels in an atom. Now, when a photon enters a solid, it can interact with these energy levels; if the photon has an energy equal to one of the lattice vibrational energy levels, then the photon is absorbed. However, if the photon has an energy greater than any of the lattice vibrational energy levels the lattice will absorb the photon, but since there is too much energy for the lattice to absorb, it releases the energy in the form of another photon. However, there is a time delay between the lattice absorbing the first photon and emitting the second while the lattice tries to absorb the photon energy. A photon may 'hop' between springs while traveling through a solid, so although photons always travel at c in a solid they 'appear' to slow down while they are absorbed and re-emitted by the energy levels.

Does that make sense?

Caveat lector - much of this (in fact the majority of it) is not scientifically accurate, but does convey the 'gist' of the mechanisms.

 

[anantchowdhary]

Im getting a hang of wat ur saying.But can u please answer my previous question based on the time taken by a photon to traverse the same distance in a refracting medium and also in vacuum.Thank you

 

[Hootenanny]

Hey,is it that the photon's time to cover that distance thru a refracting medium gets prolonged in comparison to its normal time taken to pass thru a distance?Im sry I am in a mess

Yes, in general it will take light longer to travel through a refracting medium than through free space. Although please note that photons travel at c through the refracting medium. And there's no need to apologise, we're all here to learn.

 

[anantchowdhary]

Hey so if it takes a longer time then isn't Fermat's Principle of least time being violated
Also so a photon has to be two dimensional as viewed by us,is it?Cuz it ha no length also it duznt travel thru time?

 

[Hootenanny]

Hey so if it takes a longer time then isn't Fermat's Principle of least time being violated

Not if you correctly understand the principle.

Also so a photon has to be two dimensional as viewed by us,is it?Cuz it ha no length also it duznt travel thru time?

From our point of view photons do experience time.

 

[anantchowdhary]

ohk i get ur second point but not the first.Could you please elaborate

 

[Jimmini]

ohk i get ur second point but not the first.Could you please elaborate

Einstein once said, "for every action, there is an opposite and equal reaction".
If you take Fermats' work and apply time/distance to the concept, that's what it equals.
It could be that what fermat meant by path of least time is less energy expended. For light to change direction would require a greater energy expenditure.
But to follow its' path, it will be conserving energy.
Hope this helps.

 

[cristo]

Einstein once said, "for every action, there is an opposite and equal reaction".

Whilst Einstein may have said it, this is Newton's third law!

 

[Jimmini]

Whilst Einstein may have said it, this is Newton's third law!

I like Einstein better :).