Explaining the Photoelectric Effect
Work function and threshold frequency
- When EM radiation hits a metal, the metal's surface is bombarded with photons.
- If one of these photons collides with a free electron, the electron gains this energy (\(E=hf\))
- Before an electron can leave the surface of the metal, it needs enough energy to break the bonds it is being contained by.
- This is called the Work Function energy (\(\phi\)).
- If the energy gained by the electron by the photon is greater or equal to the work function energy, then the electron can be emmitted.
- If the energy gained is less than the work function energy, the electron will shake around a bit but NOT be emitted. Because \(hf\geq \phi\) for electrons to be released, the threshold frequency must be \(f_{o}=\frac{\phi}{h}\)
Maximum kinetic energy
- The energy transferred from EM radiation to an electron is the energy it absorbs fromone photon \(hf\).
- The minimum amount of energy an electron can lose is the work function energy therefore the max kinetic energy \(E_{k(max)}\)
- This means that \(E_{k(max)}=hf-\phi\) which can be rearranged in \(hf=\phi+E_{k(max)}\)