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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

1. $0$
2. $\dfrac{q^{2}}{16\pi \epsilon d^{2}}$ away from the plate
3. $\dfrac{q^{2}}{16\pi \epsilon d^{2}}$ towards the plate
4. $\dfrac{q^{2}}{4\pi \epsilon d^{2}}$ towards the plate