### Example 1.5 Part C in 6th Edition

Posted: **Wed Oct 24, 2018 11:08 pm**

by **Dustin Shin 2I**

In the textbook there is an example of analyzing the photoelectric effect. The first two parts I understand but I don't understand part C conceptually. The questions asks us: "To find the longest wavelength of radiation that is able to eject an electron." They go on to set Ek = 0 which I do not understand. Why would they set Ek = 0?

### Re: Example 1.5 Part C in 6th Edition

Posted: **Wed Oct 24, 2018 11:51 pm**

by **Jeffrey Xiao 4A**

Since wavelength and frequency are inversely related, the longest wavelength possible corresponds to the lowest frequency possible to eject an electron, and since the equation for photoelectric effect is Ek=hv - work function, the lowest frequency that ejects an electron is when hv-work function=0 since Ephoton (hv) must be at least equal to work function to eject an electron, so Ek must be 0.