For Potassium Metal, the Work Function $\phi$ (The Minimum Energy Needed to Eject an Electron from the Needed

Multiple Choice

For potassium metal, the work function $\phi$ (the minimum energy needed to eject an electron from the metal surface) is 3.68 * 10¯¹⁹ J. Which is the longest wavelength of the following which could excite photoelectrons?

A) 550. nm
B) 500. nm
C) 450. nm
D) 400. nm
E) 350. nm