= Permittivity convention for transmitted image charges
For a real charge $Q$ in medium 1, the potential in medium 2 can be represented by the source $Q_t=2\epsilon_2Q/(\epsilon_1+\epsilon_2)$ using medium 2's Coulomb prefactor $1/(4\pi\epsilon_2)$. The same potential uses $2\epsilon_1Q/(\epsilon_1+\epsilon_2)$ if medium 1's prefactor is retained instead. These different effective source labels do not change the physical field. A decomposition $Q_t=Q+Q'$ must state which prefactor it uses.
Back to article page
