# 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 = $\frac{\mathrm{E}}{{\mathrm{N}}_{\mathrm{A}}}$ =  = 6.84 x 10-19 J.

E0 = hν0 = $\frac{\mathrm{hc}}{{\mathrm{\lambda }}_{0}}$

⇒ λ0 = $\frac{\mathrm{hc}}{{\mathrm{E}}_{0}}$ where λ0 is the longest wavelength that can eject an electron.

⇒ λ= 291 nm