Dual Nature Of Radiation

The difference between threshold wavelengths for two metal surfaces \(\mathrm{A}\) and \(\mathrm{B}\) having work function \(\phi_{A}=9 ~\mathrm{eV}\) and \(\phi_{B}=4 \cdot 5 ~\mathrm{eV}\) in \(\mathrm{nm}\) is:

\(\{\) Given, hc \(=1242 ~\mathrm{eV} \mathrm{nm}\}\)