30-07-2012, 01:19 PM
Properties of X-rays
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Properties of Electromagnetic Waves
Electromagnetic radiation can be considered as wave motion in accordance with classical theory. A – amplitude of the wave ω – frequency (ω = 2πν) ϕ – phase (ϕ = νt)
According to the quantum theory electromagnetic radiation can also be considered as a particles called photons. Each photon has associated with it an amount of energy:
X-ray Spectrum
X-rays are produced when accelerated electrons collide with the target.
The loss of energy of the electrons due to impact is manifested as x-rays.
X-ray radiation is produced in an x-ray tube.
Most of the kinetic energy of the electrons striking the target is converted into heat, less than 1% being transformed into x-rays.
The Characteristic Spectrum
The characteristic peak is created in when a hole in the inner shell, created by a collision event, is filled by an electron from higher energy shell.
Let a K-shell electron be knocked out -- the vacancy can be filled by an electron from the L-shell (Kα radiation) or the M-shell (K β radiation).
Properties of the Absorption Coefficient
There is a sharp discontinuity in the dependence of the absorption coefficient on energy (wavelength) at the energy corresponding to the energy required to eject an inner-shell electron.
The discontinuity is known as an absorption edge.
Away from an absorption edge, each “branch” of the absorption curve is given by: