Sunlight, whose visible wavelengths range from 380 to 750 nm, is incident on a sodium surface. The work function for sodium is W0 = 2.28 eV.

Find (a) the maximum kinetic energy KEmax of the photoelectrons emitted from the surface and (b) the longest wavelength that will cause photoelectrons to be emitted.

Please explain how to solve the problem as well. Thanks!