midterm problem

[Savannah Mance 4G]

On the midterm there was a question about the longest wavelength needed to remove an electron from gold. But, they only give the work function. I tried rearranging and combining formulas but I always end up with two unknown variables. How would I solve this problem? Does anyone know what combination of the formulas to use?

[Hiba Alnajjar_2C]

Given that you're looking for the longest wavelength (and therefore the least amount of incoming energy required), you can assume that the Kinetic Energy is equal to 0. Then, you could rearrange the formula so that the work function is equal to h*c divided by the wavelength. You are essentially using the main photoelectric effect equation but setting the kinetic energy equal to 0.