What type of radiation is created when an electron knocks a k-shell electron out of its orbit?

When an electron knocks a k-shell electron out of its orbit, the radiation produced is known as characteristic radiation. This type of radiation occurs because once the k-shell electron is ejected from its orbit, there is a vacancy in that energy level. An electron from a higher energy level may then fall into this lower energy vacancy, resulting in the release of energy in the form of a photon. This photon has a specific energy that corresponds to the difference in energy between the two shells involved, hence the term "characteristic."

Characteristic radiation is unique to the particular elements involved because the energy levels of electrons in atoms differ from one element to another. This makes it a distinct form of radiation that can be used to identify elements based on the emitted photon energies. Other types of radiation like Bremsstrahlung radiation, scatter radiation, and primary radiation involve different mechanisms of interaction and do not arise specifically from the ejection of inner shell electrons.