In Griffiths Electrodynamics book, he suggests that the surface charge density of a plate is given as σ=-ϵ0⁶V⁶n. Now, in the context of the problem where this shows up, you have a conducting plane that is grounded and resides at the xy-plane. There is a positive point charge q a distance dˆz above this plane. You apply the method of images, replacing this problem with one where there is a mirror charge and no conductor. You obtain the potential V, which is also the potential for the original problem for z≥0. Next, you want to find σ of the plane. Which equation should be used to find σ?
1) σ=-ϵ0⁶V⁶n
2) Eabove-Ebelow=σϵ0ˆn
3) σ=-ϵ0⁶V⁶z
4) Eabove-Ebelow=σϵ0ˆz