The threshold frequency in the context of solid-state physics differs significantly from that of isolated atoms. For a metal like copper (Cu), the first ionization energy is approximately 7.7 eV, while the work function, which represents the threshold energy for photoemission, is around 4.6 eV. This distinction highlights that properties of solids, such as energy bands, are not simply an aggregation of atomic properties. Understanding these differences is crucial for accurately discussing concepts like threshold frequency and ionization energy.
PREREQUISITESStudents and professionals in physics, particularly those focusing on solid-state physics, materials science, and semiconductor technology, will benefit from this discussion.
Clara Chung said:For example a metal atom have 3 electrons which occupies 2 energy level. Is the threshold frequency = the energy needed to bring an electron in E2 to E(infinity) / h?
Thanks for telling me that an atom from a metal has different properties from a metal.ZapperZ said:You need to understand one very important concept here. When atoms are together to form a solid, many of the individual properties of isolated atoms are no longer relevant. A solid has many properties that an individual atom does not have. This includes the formation of "energy bands" in solids, whereas in atoms, you have discrete energy levels.
So your question here doesn't make any sense because you are asking a question about a "metal", which is a solid, based on the valence shell of an individual atom. While this may be relevant when one probes deeper energy state of the metal, it is no longer relevant when you talk about "threshold" frequency or energy to cause the first ionization.
For example, the first ionization energy of Cu atom is ~7.7 eV. Yet, for Cu metal, the work function, and thus, the threshold energy for photoemission, is ~4.6 eV. These two numbers are different!
More is Different! Solid state physics is not simply "a lot of atomic physics".
Zz.