Our results from the Debye–Hückel or Thomas–Fermi approximation may now be inserted into Poisson's equation. The result is [ ∇ ∇ 2 − − k 0 2 ] ϕ ϕ ( r ) = − − Q ε ε 0 δ δ ( r ) , which is known as the screened Poisson equation. The solution is ϕ ϕ ( r ) = Q 4 π π ε ε 0 r e − − k 0 r , which is called a screened Coulomb potential. It is a Coulomb potential multiplied by an exponential damping term, with the strength of the damping factor given by the magnitude of k 0, the Debye or Thomas–Fermi wave vector. Note that this potential has the same form as the Yukawa potential. This screening yields a dielectric function ε ε ( r ) = ε ε 0 e k 0 r .