Final exam 2013 Fall Q2A

[704709603]

Hi,
Q: e- ejected from sodium. if wavelength of ejected e- is 1.1 nm, what was the frequency of the incident light? work fxn for sodium =150.6kJ/mol
Why do we need to find the velocity of the ejected electron first? Why can't we use E=h(nu) to find the Ek? Is it because the electron comes out at a certain velocity that is necessary to know and we can't ignore? Does is make a difference was metal the electron is ejected from? Why we need to convert to particles instead of moles for the work function; because we have to think in quantum mechanics now?

Thank you!

[Mizuno_Mikaela_1D]

You need to find the velocity of the electron first in order to calculate the kinetic energy of the electron. You can't use E=h(nu) to find the Ek because you don't have the frequency of the ejected electron. I think it does make a difference which metal the electron was ejected from but I'm not sure how. However, all the numbers needed for solving the equation should be given. You need to convert to particles instead of moles for the work function, because you need energy in the unit joules per electron.

[704709603]

Thank you!