Understanding cut off wavelength at edge of Bremsstrahlung region

In summary, the page discusses the process of bremsstrahlung radiation and the relationship between electron energy and photon energy. It mentions a cut off wavelength for photons to obtain their full energy from electrons and states that the minimum wavelength is 12.4 / V, where V is the voltage in kilovolts. The book's equation, λ = 12.4 / V, is derived from the relation between electron energy and photon energy. The reason for using λmin instead of just wavelength is because it represents the maximum energy the photon can have.
  • #1
Jimbo
10
0
Hello,

I am trying to understand an equation stated in the book 'Principles of Protein X-Ray Crystallography' by Jan Drenth (The exact page I am reffering to can be found here: http://books.google.co.uk/books?id=...y crystallography&pg=PA24#v=onepage&q&f=true")

The page discusses electrons being accelerated between a cathode and an anode, and the x-rays emitted as part of the process. It mentions a cut off wavelength where "photons obtain their full energy from the electrons when they reach the anode", and states that electron energy = electron charge * accelerating voltage and that photon energy is planks constant * (speed of light / wavelength) and that the minimum wavelength is therefore 12.4 / V where V is in kilovolts.

My working is as follows:

When the photons obtain their full energy from the electrons, eV = hc / λ

So, λ = hc / eV (as stated in the book)

hc = 1.24 * 10-6 eVm

So just looking at the units I get:

eVm / eV which makes sense as I am left with m for the wavelength.

But my question is where does the V come from in the books equation? (They state that λ = 12.4 / V)

Also why is this necessarily the minimum wavelength? (it is stated as λmin) Why not just wavelength?

Sorry for the long introduction but I wanted to give my question a bit of context.

Thanks very much for any guidance,

Jimbo
 
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  • #2
The process that creates the X-rays is bremsstrahlung radiation, in which a fraction of the electron's energy goes into the photon. The maximum energy the photon can have is 100 percent of the electron energy, and this corresponds to the shortest wavelength the photon can have, λmin. The electron energy when it arrives at the cathode is e*V, charge e times voltage V.
 

1. What is the Bremsstrahlung region?

The Bremsstrahlung region is a specific range of wavelengths in the electromagnetic spectrum where the majority of Bremsstrahlung radiation is emitted. This type of radiation is produced when charged particles, such as electrons, are accelerated or decelerated by the electric fields of atoms or ions in a material.

2. How is the cut off wavelength at the edge of the Bremsstrahlung region determined?

The cut off wavelength at the edge of the Bremsstrahlung region is determined by the energy of the charged particles, as well as the atomic number and density of the material. As the energy of the particles increases, the cut off wavelength decreases. Additionally, materials with higher atomic numbers and densities will have lower cut off wavelengths.

3. What is the significance of the cut off wavelength at the edge of the Bremsstrahlung region?

The cut off wavelength at the edge of the Bremsstrahlung region is significant because it represents the maximum wavelength of radiation that can be emitted in this region. Any radiation with a longer wavelength will not be produced in the Bremsstrahlung process.

4. Can the cut off wavelength at the edge of the Bremsstrahlung region be changed?

Yes, the cut off wavelength at the edge of the Bremsstrahlung region can be changed by altering the energy of the charged particles or by using different materials. Higher energy particles or materials with higher atomic numbers and densities will result in shorter cut off wavelengths.

5. How does the understanding of the cut off wavelength at the edge of the Bremsstrahlung region impact scientific research?

Understanding the cut off wavelength at the edge of the Bremsstrahlung region is important in many areas of scientific research, including medical imaging and nuclear physics. It allows researchers to accurately predict and control the emission of Bremsstrahlung radiation, which is used in various applications such as X-ray production and particle accelerators.

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