X-ray production
Contents
1.3. X-ray production#
X-rays can be produced by accelerating electrons at targets with a large number of protons (\(Z\)). The electrons emit a continuous spectrum of radiation (Bremsstrahlung) as they are slowed down and their kinetic energy is converted into x-ray photons. However, there is a minimum wavelength below which no x-rays are observed. Figure 1.8 shows a characteristic x-ray spectrum, the minimum wavelength cutoff is clearly seen where the x-ray intensity drops to zero at short wavelengths.
For electrons accelerated through a potential \(V\) the maximum kinetic energy they can gain is given by \(qV\). Hence, when an electron gives up this energy to a single photon the maximum energy it can have is given by
Where \(f_\text{max}\) is the maximum allow photon frequency \(\lambda_\text{min}\) is the equivalent minimum allow wavelength. The process is equivalent to a reverse of the photoelectric effect.
The x ray tube used to produce the data in figure 1.8 was operated at 60 kV. Does equation (1.3) give the correct value for the minimum wavelength?
20.7 pm looks sufficiently close the the lower wavelength in the figure to say that this appears to be correct.
1.3.1. References#
(fig) LinguisticDemographer at English Wikipedia, Public domain, via Wikimedia Commons