# Potential below a grounded conducting plane

If I have a charge $$q$$ above a grounded conducting plane, I know I can calculate the potential of the charge using image method. Since the plane is grounded, would the potential below the plane be $$V=0$$, assuming there is no charge below the grounded conducting plane?

You are right, an infinite grounded conducting plane will shield the lower $$1/2$$ plane from charges above the plane. If the plane has $$0$$ resistivity, it will also shield changing magnetic field sources, such as currents and magnets.