## Sample Test Problems

1. What is the maximum wavelength of electromagnetic radiation which can eject electrons from a metal having a work function of 3 eV? (3 points)
The minimum photon energy needed to knock out an electron is 3 eV. We just need to convert that to wavelength. 2. * Based on classical electromagnetism and statistical mechanics, Rayleigh computed the energy density inside a cavity. He found that, at a temperature T, the energy density as a function of frequency was Why is this related to black body radiation? Why was this in obvious disagreement with observation?
3. What is the maximum wavelength of electromagnetic radiation which can eject electrons from a metal having a work function of 2 eV?
4. * State simply what problem with black-body radiation caused Plank to propose the relation for light.
5. The work function of a metal is 2 eV. Assume a beam of light of wavelength is incident upon a polished surface of the metal. Plot the maximum electron energy (in eV) of electrons ejected from the metal versus in Angstroms. Be sure to label both axes with some numerical values.

Jim Branson 2013-04-22