X-rays are produced when fast-moving electrons impinge on matter. The phenomena
resulting from the deceleration of such electron are very complex, and X-rays result
from two general types of interaction of the electron with the atoms of the target
material. X-rays are electromagnetic waves, and as such are accompanied by
periodically changing field as they proceed outward from their source. An electron
in path of such a wave is excited to periodic by changing field , and itself becomes
a source of electromagnetic waves of the same frequency and wavelength. An atom is
made up of a positively charged nucleus surrounded by a cloud of electrons, one for
each increment of nuclear charge , the number being equal to the atomic number of
the element i n question. The scattered waves from the several electrons in an atom
combine , so that the scattering effect an atom is essentially
that of appoint source of scattered X-ray.