Potassium has a work function of 2.4 eV. What is the longest wavelength of light that may cause K to undergo the photoelectric effect?

Question

Potassium has a work function of 2.4 eV. What is the longest wavelength of light that may cause K to undergo the photoelectric effect?

Answer 1

Well let's look at the equation first and it should be easy.

KE_e = hf - work function (also called binding energy BE)

this equation reallllly looks like it takes the form of y = mx + b which is the equation of a line. So at some point KE_e equals zero which means that there is no kinetic energy of ejected electrons.

So 0 = hf - BE

BE = hf

solve for frequency (f) which will be units of 1/s

From frequency we can acquire wavelength using another equation

lambda = C/f where C equals speed of light and lambda is wavelength. Good luck!