Lesson plan
Absorption edge
In physics, an absorption edge (also known as an absorption discontinuity or absorption limit) is a sharp discontinuity in the absorption spectrum of a substance. These discontinuities occur at wavelengths where the energy of an absorbed photon corresponds to an electronic transition or ionization potential. When the radiation energy is far away from an absorption edge, the absorption spectrum follows a smoothly decreasing function that is proportional to 1/E^3 . However, when the energy matches the binding energy of an electron in an atom the absorption spectrum sharply increases. This is due to the new absorption mechanism (i.e. the process of ionizing the atom by converting all of the quantum energy of the photon into the energy required to overcome the ionization potential). When the quantum energy of the incident radiation becomes smaller than the work required to eject an electron from one or other quantum states in the constituent absorbing atom, the incident radiation ceases to be absorbed by that state. For example, incident radiation on an atom of a wavelength that has a corresponding energy just below the binding energy of the K-shell electron in that atom cannot eject the K-shell electron. Siegbahn notation is used for notating absorption edges. In compound semiconductors, the bonding between atoms of different species forms a set of dipoles.…
Article summary
In physics, an absorption edge (also known as an absorption discontinuity or absorption limit) is a sharp discontinuity in the absorption spectrum of a substance. These discontinuities occur at wavelengths where the energy of an absorbed photon corresponds to an electronic transition or ionization potential. When the radiation energy is far away from an absorption edge, the absorption spectrum follows a smoothly decreasing function that is proportional to 1/E^3 . However, when the energy matches the binding energy of an electron in an atom the absorption spectrum sharply increases. This is due to the new absorption mechanism (i.e. the process of ionizing the atom by converting all of the quantum energy of the photon into the energy required to overcome the ionization potential). When the quantum energy of the incident radiation becomes smaller than the work required to eject an electron from one or other quantum states in the constituent absorbing atom, the incident radiation ceases to be absorbed by that state. For example, incident radiation on an atom of a wavelength that has a corresponding energy just below the binding energy of the K-shell electron in that atom cannot eject the K-shell electron. Siegbahn notation is used for notating absorption edges. In compound semiconductors, the bonding between atoms of different species forms a set of dipoles.…
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
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