Quantum physics IB #3 work function and einstein

Hey guys, I just realised that I forgot to explain one of the formulas on the formula booklet!
E_max = hf - work function.
Here, E_max is the maximum energy of the ejected electron. Keep in mind we use the word maximum because electron kinetic energies come in a range, and KE of the electron ejected may decrease if it has to pierce through multiple layers of the metal lattice.
hf is the energy of light, and the work function is the energy required for the electrons to overcome the electrostatic forces of attraction between it and the positive metal ions. After the energy from the light is used to overcome the work function, the remaining energy becomes the KE of the electron.
I hope this explanation is clear!

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