December 13, 2011

X-Ray Spectra!

This post will either be boring or extremely fascinating, depending on whatever floats your boat.

The minimum wavelength of an x-ray occurs when all the energy of the accelerated electron is converted into an X-ray photon in a single collision. However, most of the accelerated electrons are stopped after a few collisions. Different electrons convert different amount of their kinetic energies into X-ray photons of different wavelengths, resulting in the continuous background spectrum.

Using an X-ray spectrometer and a crystal as a wavelength selector, the intensity of X-rays emitted as a function of its wavelength can be measured and then plotted.

The X-ray spectrum.

The X-ray spectrum consists of a continuous background of X-ray radiation and a series of characteristic lines with intensity peaks. 

In the continuous background, the intensity varies smoothly with wavelength. The background intensity reaches a maximum value as the wavelength increases and then falls as the wavelength increases further.

The characteristic X-ray spectrum which consists of sharp peaks of high intensity occurs at specific wavelengths, unaffected by the voltage of the X-ray tube.

The peaks are a result of the electrons from the cathode knocking out inner shell electrons from the target atoms. When the vacant shells are refilled by free electrons, X-ray photons of specific wavelengths are emitted.

Witness my awesome paint skills.

Painstakingly painted in MS Paint.

The figures above show the mechanism behind the characteristic X-ray spectrum.

What's the K and L in the Graph? What do they stand for?

Until next time.


  1. This is a bit too high level for me but I unterstand the must I guess and its very interesting! Looking forward to other posts like this

  2. So, if the electrons knock out other electrons, to get the X-Ray scan...
    Maybe if we knock out neutrons or protons... we can get some sort of SUPER X-Ray? To see through walls? Or Just blow up the world.

  3. Fascinating stuff. Do gamma rays function the same way?

  4. I always wonder about things like this. Where does the other electron go?


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