X-rays are just like any other kind of electromagnetic radiation. They can be produced
in packets of energy called photons, just like light. There are two different atomic
processes that can produce X-ray photons. One is called Bremsstrahlung (a German
term meaning “braking radiation”) and the other is called K-shell emission. They can
both occur in the heavy atoms of tungsten which is often the material chosen for the
target or anode of the X-ray tube.