<p>In a photoelectric experiment, photons of energy 5 eV strike a cathode C&prime; and cause emission of photoelectrons. The maximum kinetic energy of these photoelectrons is 2 eV. Now, photons of energy 6 eV are incident on the same cathode C&prime;. Determine the stopping potential Vs that must be applied to the anode A relative to C&prime; so that no photoelectron reaches the anode.</p>