I have the eqns, and have started out on these problems...but I'm not sure where to go at certain points. 1.) It takes 1.9 eV to free an electron from cesium. a.) Find the longest wavelength light which can free the electron. Well, we have the general equation from the photoelectric effect Ephoton = Eeject + kinetic Ephoton >= Eeject in order to free an electron. Therefore: hc/lambda >= Eeject [h/(1.609*10^-19)]*c/Eeject >= lambda I'm not sure if this is lambda max though. b.) Find the potential required to stop th eelectron if the incident light is 250 nm, and 350 nm. I'm basically using the same equation as before, but solving for energy, by plugging in lambda. Is this correct? _ _ _ _ _ _ 2.) In the double slit experiment (slits separated by distance d), with a light bulb behind the slits, what momentum photons will disturb the interference pattern? What type of light is this (e.g. visibile, X-Ray), and what about if d is atomic size? Now the interference is disturbed IF d > lambda. But what equation should I use for this? hc/lambda again? When doing that, I got: hc/lambda >= 1ev (because it's one electron). Is this the way to go? Once again, thanks for any and all help, I have a few more questions, but I want to work on them some more. I would go to office hours as well...but it's snowing HARD!