Continuous X-rays

Bremsstrahlung transitions create the phenomenon of continuous x-rays whereas regular characteristic x-rays are created by inner shell transitions. Bremsstrahlung mechanism can be viewed when a target made of metal suffers electron bombardment. The atoms of the metal target scatter the electrons, whose change in acceleration causes a phenomenon of radiation in them.

Just like the phenomenon of visible light, continuous X-ray spectra also contains photons ranging through a lot of wavelengths. As we all are well aware by now, the production of X-rays happens when the target which is made up of an element with high atomic number is hit by electrons travelling at a high velocity. Most of the energy applied is wasted by being converted into heat energy in the target material’s system. X-rays that have continuously unstable wavelengths are produced due to the loss of energy that the few electrons who were moving fast enough (and penetrated to the interior sections of the atoms of the material being targeted), suffer. The attractive pulling forces applied by the nucleus of the target element causes a deceleration of these fast moving electrons in turn decreasing their energy continuously. A varying frequency of X-rays is emitted continuously due to the retardation of the speed of electrons. The X – rays consist of continuous range of frequencies upto a maximum frequency ímaxor minimum wave length ?min. This is called as continuous X – rays. The minimum wave length depends on the anode voltage. If V is the potential difference between the anode and the cathode.

eV = h?max = hc / ?min

The minimum wavelength of the given radiation is,

?min = hc /eV

Where the Planck’s constant is h, the velocity of light is c and the charge of the electron is e. Substituting the known values in the above equation, we get

?min = 12400/V A0

For these specific operating voltages, the minimum wave length is same for all metals.

Practise This Question

Two charges of equal magnitude 'q'  but of opposite sign separated by a distance 2a constitute an electric dipole of dipole moment p. If P is a point at a distance r from the centre of the dipole and the line joining the centre of the dipole to this point makes an angle θ with the axis of the dipole, then the potential at the point P  is given by  (r2a) (Where p=2qa )