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How do X-rays form when fast electrons are suddenly stopped in an X-ray tube?

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Diagram of a tree leaf illustrating photosynthesis, with arrows showing sunlight, water, and carbon dioxide entering the leaf and sugars and oxygen being produced. A person is shown beside the tree to demonstrate the exchange of oxygen and carbon dioxide between plants and animals. — electromagnetic radiation Diagram of photosynthesis showing how water, light, and carbon dioxide are absorbed by a plant to produce oxygen, sugars, and more carbon dioxide.

In an X-ray tube, X-rays are produced when high-energy electrons, accelerated by a high-voltage field, strike a metal target (the anode). As these fast-moving electrons interact with the target atoms, they undergo sudden deceleration or deflection due to the strong electric fields of the atomic nuclei.123

This process of abrupt "braking" causes the electrons to emit electromagnetic radiation known as bremsstrahlung (German for "braking radiation"). Because electrons may be stopped in a single collision or deflected multiple times before coming to rest, they release energy in a continuous spectrum of photons ranging from low energies up to a maximum value determined by the initial kinetic energy of the electrons.143

While this continuous bremsstrahlung spectrum accounts for the majority of the radiation produced, the tube also generates "characteristic radiation" when electrons collide with target atoms, ejecting inner-shell electrons and causing outer-shell electrons to fill the resulting vacancies.43