When a charge is placed next to an uncharged conductor, a mirrored image of that charge is created on the other side of the uncharged conductor. The mirrored image charge will have an equal and opposite magnitude to the original charge. For example, if there was a 1C point charge 1m away from a thin metal sheet, it will appear as if there is a -1C point charge on the other side of this metal sheet. The electric field lines in the x direction would look like this: +o--------->|--------->o- Why does this happen? All I know so far is that when a conductor is placed inside an electric field, the charges inside it are re-arranged. This seems intuitive, as an electric field is just a vector field that denotes what force a positive 1 coulomb charge would feel a particular point in space, so the charges inside the conductor will have a force on them, and will move until they are in a position where there there is no net force on them. This will be when the electric fields inside the conductor cancel out. In my example diagram the positive charge will cause the electrons inside the conductor to move towards this charge, they will continue moving until the fields cancel out. I can see that this would also be true if an opposite charge was placed at the other side of the conductor. The electrons inside wouldn't be able to tell the difference. But just because this is true does not mean that the fields on the right side of the conductor will act as if there is a mirror charge there. I don't understand why a mirror charge is created. Will someone please explain? Thanks. Also, mini extra question: How does this apply to antenna's? It's something to do with dipoles but I don't properly understand what is happening. If you could give an example of mirror charges being created in the context of an antenna It will be greatly appreciated!