A monochromatic light of frequency is incident on a metal surface and ejects photoelectrons. The photoelectrons having maximum kinetic energy are just able to ionise a hypothetical atom in ground state. The energy levels of hypothetical one-electron atom' are given by `E_(n)=-(29)/(n^(2)) eV`, where n = 1,2,3.....When whole experiment is repeated with an incident light of frequency `v//2`, the photoelectrons with maximum kinetic energy are just able to ionise hydrogen atom in ground state. Calculate the work function of the metal