1) The maximum kinetic energy of photoelectrons is 2.8eV. When the wavelength of the light is increased by 50%, the maximum energy decreases to 1.1 eV. What are the "work function" of the cathode and the "initial wavelength"? K.E.initial=K.E.max=2.8eV=4.48x10^-19J lambda.final=1.5*lambda.initial Final energy = 1.1 eV (<---is this purely kinetic energy? why?) K.E.max = hc/(lambda.initial) - work function But now I have 2 unknowns: work function and lambda.initial, what can I do to solve for both? I am stuck here... Does anyone have any idea or insight? Any help is greatly appreciated.