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Excitation and the photoelectric effect.

When an electron is excited by a free electron or photon, it goes up an energy level, and then falls to the ground state and emits a photon. Why does the photoelectric effect allow electrons to be removed from the metal instead of simply falling back down? Is it because metal is a good conductor, or can photoelectrons be released in interactions with nonmetals? Thanks in advance.
Original post by Physstudent1
When an electron is excited by a free electron or photon, it goes up an energy level, and then falls to the ground state and emits a photon. Why does the photoelectric effect allow electrons to be removed from the metal instead of simply falling back down? Is it because metal is a good conductor, or can photoelectrons be released in interactions with nonmetals? Thanks in advance.


You have the right idea about metal being a good conductor. It has many free electrons roaming around, commonly referred to as a 'sea' of electrons.
These electrons require little energy to liberate them from the metallic surface.
The underlying physics to the photoelectric effect is common to all atoms (i.e absorb photon, electrons absorb energy etc) however the free electrons in metal can accept a broader range of photon energies than the non-metallic materials, which are restricted by quantum constraints to accept only certain light frequencies.
Due to this, the metal electrons undergo the full photoelectric effect and release photoelectrons, however non-metal substances only absorb certain energies of photons that only raise energy levels for the electrons. With a high enough energy (and certain materials) you can release electrons from non metalloid substances, in the compton effect of gamma rays.
And you're most welcome :smile:

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