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Let's examine how is X-ray produced, the

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fundamental physics behind the X-ray production.

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So let's examine the first type of X-ray production called the

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Bremsstrahlung process.

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What is Bremsstrahlung process? It is also called as

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breaking X-rays.

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So what I'm showing here is when an X-ray are produced by

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conversion of electron kinetic energy into

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electromagnetic radiation.

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So when electron interact with the external radiation,

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interact with the matter, which are closest to the nucleus,

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higher kinetic energy is lost, yields higher energy

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X-ray photon. Like here, when this is a incident

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electron are hitting or interacting with a

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matter, let's say, if they are getting closer to

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this one, they get deflected. When they get deflected,

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they change the amount, they lose some energy, and the remaining energy they

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carry out, and the balance of the energy is released as a

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type of a X-ray called the Bremsstrahlung radiation.

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The Bremsstrahlung radiation, therefore, only have very

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few X-ray photon at the maximum energy, and rest

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of it are lower than energy. And that is the fundamental behind

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this X-ray spectrum forming.

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So if the energy of the electron is 90 keV from the cathode

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hitting the anode,

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all of them are not converted into 90 keV X-rays.

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Some of it is converted much lower because that is the principle behind

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here. So this is the incident electron interacting with the

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target atom. So when this is reflected back here,

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this is impact with nucleus maximum energy reflected back, or

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if it interact much lesser, this is called the distant

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interaction, low energy. If it acts in between, it's called the moderate

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energy. All of this is captured, and if you map them,

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we get what is called as a relative output on the X-ray

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energy as something like this, like flowing here.

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So generally, it should be like this, but the spectrum looks like this.

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Why? Because we can filter this to remove

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this low energy, which is not contributing to the image formation,

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therefore, the spectrum looks like this.

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There is a second type of X-ray production called the characteristic X-rays.

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When energy of the incident electron

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exceed the binding energies of inner shell electron of a target

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nuclei,

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it can result in ejection of inner shell electron.

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So when this incident interact here, and the energy is quite

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larger than the binding energy of the K-shell,

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that electron is rejected, and that's called a ejected

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K-shell electron.

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Now, there is electron from outer shell will immediately

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replace and fill the vacancy. The difference

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in the energy between these two are released as an X-ray.

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This is here, the X-rays, and that we call it as a characteristic

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X-ray. Because these X-rays all come out with the

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same energy as the difference between the two, L-shell and

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K-shell. Therefore, the X-rays produced are all of a

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uniform energy.

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So you can see here, this is a spectrum.

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This is a Bremsstrahlung spectrum.

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However, this is a spectrum, let's say, for iodine.

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Iodine, at certain energy, will absorb the K

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electron, and the difference in the electron between the higher and

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lower shell is released as a characteristic X-ray, and this is the

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characteristic X-rays. You're shown here is a tungsten

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target, which is a typical anode of an X-ray tube.

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These k spikes are produced. What is an X-ray signal?

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An X-ray signal results from differential attenuation.

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Different amount of stopping power of the material, which is

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interacting with the X-rays. So some ray path produce

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more attenuation than the others,

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and some materials produce more X-ray collision,

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and some paths are longer, providing more opportunity for collision.

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These are the physics behind the formation of an X-ray

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signal.