Work function of metal A is equal to ionization energy of Hydrogen atom in its ground state. Work function of metal B is 7.2 eV. Light of same wavelength is incident on A and B. The maximum kinetic energy of emitted photoelectrons from B is twice that of photoelectrons emitted from A. The wavelength (in $\text{Å}$) of incident light is (Take hc = 12400 eV $\text{Å}$ )