1. The problem statement, all variables and given/known data What is the maximum kinetic energy (in eV) of a photoelectron emitted when a surface, whose work function is 5eV, is illuminated by photons whose wavelength is 400 nm 1. -1.89 2. 1.89 3. 0 4. 3.1 2. Relevant equations hc/(lambda)=work function + KE max 3. The attempt at a solution After plugging numbers in the formula above, I get KE max=-1.89 eV, but I guess I must have done something wrong, since energy cannot be negative.