# Light in electrostatic potential

1. Mar 10, 2009

### lightarrow

Is electromagnetic radiation affected, in any way, by a strong electrostatic field (or gradient of field)? Specifically, is it possible to reflect light with such a field or to confine an EM wave inside an electrostatic potential well?

2. Mar 10, 2009

### xepma

From a classical point of view: no. Light does not interact with itself, therefore the resulting electromagnetic field would just be the sum of the electrostatic field and the radiated field.

From a quantum point of view scattering between photons is possible through the exchange of virtual electrons/positrons. However, it's contributions are of order $\alpha^4$ and higher, so these effects are severely suppressed.

But come to think of it, the electrostatic field doesn't store any momentum (you need a magnetic field as well for that), but the radiated field does. Conservation of momentum in the direction of propagation cant be violated, so reflection would be impossible.

3. Mar 10, 2009

### v2kkim

If photons got scattered then do they change courses ? How about wave lengths ?

4. Mar 11, 2009

### akhmeteli

You may wish to google "delbruck scattering" - this is scattering of light in the Coulomb field of a nucleus.