Photoelectric Effect

In the photoelectric effect, the photon is completely absorbed by an atomic electron. The electron then has enough energy to escape the atom, ionizing the atom. The resulting kinetic energy of the photo-electron is equal to the photon energy minus the electron binding energy:

E_{e^-} = E_{photon} - E_{binding}

The linear attenuation coefficient for the photoelectric effect is proportional to atomic number and inversely proportional to photon energy:

\tau \propto \frac{Z^c}{E^3}

Where c is in the range of 4-5. The photoelectric effect is the most dominant for lower-energy ionizing photons and high-Z materials. For example, it plays an important role in diagnostic x-ray imaging (e.g. radiography, CT), and is the reason why bone tissue is easily visible on these images.

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