Exercise 8 | Early Quantum Theory

The minimum energy E required to eject electrons from silver is 412 kJ.mol-1.

Find the longest wavelength of electromagnetic radiation that can eject an electron.

Ek = hν - hν0  (photoelectric effect)
At the longest wavelength that can eject an electron: ν = ν0


E0 = hν0  where E0 is the minimum energy to eject one electron from silver (in J).
E0 = ENA = 412 × 103 J.mol-16.022 × 1023 mol-1 = 6.84 x 10-19 J.


E0 = hν0 = hcλ0

⇒ λ0 = hcE0 where λ0 is the longest wavelength that can eject an electron.

⇒ λ= 291 nm