Copper has a work function of 4.7eV, while gold has a work function of 5.1eV. What are the minimum frequencies of light needed to emit electrons off each metal? Suppose a lamp is made which shines light of the exact minimum frequency needed to emit electrons off of gold. If this lamp shines onto copper, with what speed are electrons emitted from the copper?
Hint: Use Planck's constant in electron Volts, h = 4.1357×10-15 (eV)s. The mass of an electron is always the same (look it up).
Answers: for copper f0 = 1.14×1017 Hz, for gold f0 = 1.23×1017 Hz. Electrons are emitted from copper with speed 3.75×106 m/s.