X-Ray Production


Why should the target at anode of a x-ray tube have atomic number greater than or equal to 74?


X-rays are produced by the interaction of the electrons from the cathode ray with electrons which are very tightly bound to their nucleus in an atom. Only in the heavier elements is the binding energy of the inner electrons sufficient to allow x-ray production. The interaction of the cathode ray electrons with the outer electrons in an atom produce photons in the visible and ultra-violet part of the EM spectrum.