A novel variational principle in electrostatics and its consequences

• Electrostatic field lines have features common to light rays in geometrical optics.
• A novel variational principle in electrostatics is introduced.
• It resembles Fermat's principle in optics.
• The principle can be used to deduce the ‘mirror equation’ for conducting sphere image problem.

We propose a novel variational principle in electrostatics and show that one can derive mirror equation in the context of image problem starting from this principle.