- #1
cesiumfrog
- 2,010
- 5
What is the classical microscopic mechanism for absorption of EM waves?
Consider a free charge isolated in the middle of a well-lit pot of (clear) honey. An external electric field will apply a force to the charge but as the charge develops a velocity it will begin doing work against friction. An incident plane EM wave should cause simple harmonic (transverse) motion of the charge, and the friction should heat the honey, but where does this energy come from?
The transverse motion of the charge should produce its own (symmetric) EM waves. Its portion in one direction may cancel some energy out of the incident beam (this is how mirrors work), but it seems as though the same amount of energy escapes in the (equal and opposite) portion (there is nothing to cancel the scattered/reflected beam). How is this all balanced?
Consider a free charge isolated in the middle of a well-lit pot of (clear) honey. An external electric field will apply a force to the charge but as the charge develops a velocity it will begin doing work against friction. An incident plane EM wave should cause simple harmonic (transverse) motion of the charge, and the friction should heat the honey, but where does this energy come from?
The transverse motion of the charge should produce its own (symmetric) EM waves. Its portion in one direction may cancel some energy out of the incident beam (this is how mirrors work), but it seems as though the same amount of energy escapes in the (equal and opposite) portion (there is nothing to cancel the scattered/reflected beam). How is this all balanced?