When light of wavelength 1 is incident on the cathode of a photoelectric tube, the maximum kinetic

Question:

When light of wavelength λ1 is incident on the cathode of a photoelectric tube, the maximum kinetic energy of the emitted electrons is 1.8 eV. If the wavelength is reduced to λ1/2, the maximum kinetic energy of the emitted electrons is 5.5 eV. Find the work function Φ of the cathode material.