# Quantum mechanics

1. Dec 8, 2005

### sweetvirgogirl

Charges of +q and -q are separated by a distance L.

What would be a typical energy of a virtual photon they exchange?

2. Dec 9, 2005

### emptymaximum

what have you done so far?

why would they exchange a virtual photon in the first place?

3. Dec 9, 2005

### dextercioby

Why do you mix photons with "distance L" ...?

Daniel.

4. Dec 9, 2005

### sweetvirgogirl

I stated the problem as it is given in the book

5. Dec 9, 2005

### dextercioby

Well, virtual photons are terms used in QED, but "distance L" between 2 pointlike charges has to do with classical electrodynamics, i.e. electrostatics...Do you see anything suspicious...?

Daniel.

6. Dec 9, 2005

### emptymaximum

draw the feynman diagram. do conservation of momentum.
treat it like a collision.

7. Dec 9, 2005

bump

8. Dec 9, 2005

### El Hombre Invisible

Can you not just use the time version of the uncertainty principal to determine the energy of the virtual photon? You can express $$\Delta t$$ in terms of L and c and find $$\Delta E$$.