For Potassium Metal, the Work FunctionΦ (The Minimum Energy Needed

Multiple Choice

For potassium metal, the work functionΦ (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