Light is an electromagnetic wave, with an electromagnetic field. Does it attract/repel charge?
Asked
Active
Viewed 103 times
0
-
3Does this answer your question? Does a photon attract or repel matter? – Mauricio Jan 31 '23 at 15:50
-
@Mauricio, not really. I think it's too complex for me. But what you were writing as an answer did enlighten me (pun intended) somewhat. If an electromagnetic wave goes by a negative charged particle, I guess that it makes sense that it interacts with it, and this is the equivalent of absorbing a photon and emitting a less energetic one, right? – Rich Hard Fine Man Jan 31 '23 at 15:59
-
Light is the attraction and repulsion itself between charges. – RC_23 Jan 31 '23 at 16:38
1 Answers
2
Let me give a answer in limit of large wavelengths with respect to the charged object:
Light (in the vacuum) has no charge, it is composed of transverse electric and magnetic fields (EM waves).
In the frame of reference of a given point charge, electromagnetic waves do not attract/repel but push or pull the charge perpendicular to the propagation direction depending on the shape of the wave in time and space.
Note that if it is a charged composite object, other forces can appear depending on the material.
Example: Suppose that you have a source of coherent light and a positive charge fixed in space. Suppose that electric field is described by a sine wave in time with a given period such that it propagates in the $x$-direction and when the electric field is positive it applies a force to the charge up in the $y$-direction. At $t=0$ there is no electric field, after 1/4 of the period it applies a force to the charge up in the $y$-axis, after 1/2 period it does nothing again, after 3/4 of the period it applies a force down on the $y$-axis an so on.
Disclaimer: in the other limit where the wavelength is compared to the size of the charged object, there are many effects that depend on the specific configuration including quantum and relativistic effects. For more details check Does a photon attract or repel matter? and the answers there. Note also that light carries momentum and can be used as light sail.
Mauricio
- 5,273