The force on a point charge $+q$ kept at a distance $d$ from the surface of an infinite grounded metal plate in a medium of permittivity $\epsilon\:$ is
- $0$
- $\dfrac{q^{2}}{16\pi \epsilon d^{2}}$ away from the plate
- $\dfrac{q^{2}}{16\pi \epsilon d^{2}}$ towards the plate
- $\dfrac{q^{2}}{4\pi \epsilon d^{2}}$ towards the plate