申論題

8. X rays with wavelength λ = 1.24 Å eject photoelectrons from a gold foil. The electrons form circular paths of radius r in a region of magnetic field B. Experiment shows that rB = 1.82×10^-4 tesla-m. Find the work function of the gold foil in electron volts. ( Electron rest mass me = 9.1×10^-31 kg )