Question

64. What is the longest wavelength of radiation that can eject a photoelectron from potassium, given the work function of potassium 2.24 eV

Answer 1

Wf = 2.2 eV = 2.2 * 1.6E-19 * 1 = 3.52E-19 Joules

since the charge on an electron is 1.6E-19 Coulombs

Wf = h f = h c / λ

λ = h c / Wf = 6.62E-34 * 3.00E8 / 3.52E-19

λ = 5.64E-7 m

λ = 564 mμ (visible light = 400-700 mμ)