Gamma and x-rays belong to a group of electromagnetic radiation. Unlike radio waves and visible light, gamma and x-rays have shorter wavelengths (or higher frequency) so it has a much higher energy. While the alpha and beta radiation has a maximum coverage is limited, so that the photons interact in a probabilistic maximum coverage of a photon can be quite varied (not sure). Nevertheless, the total fraction of photons absorbed by the material decreases exponentially with the thickness of the material.
There are three mechanisms of how gamma and x-rays interact with matter, namely the photoelectric effect, Compton and pair production hambran. External gamma radiation has hazards due to radiation provides far more energy and further when compared with alpha and beta radiation.
a. Photoelectric effect
In the process fotolistik effects, radiation of electromagnetic waves (photons) coming of atoms, as if the 'pound' one electron orbital and gives all its energy. If a given photon energy larger than the binding energy of electrons, the electrons can be detached from the atoms and produce ions. Electrons are removed (or so-called photoelectron) can cause secondary ionization events in the surrounding atoms in a manner similar to that carried out the beta. The photoelectric effect is very likely to occur if the photon has low energy (less than 0.5 MeV) and the material has a large mass (large atomic number). As an example of the photoelectric effect occurs more frequently in lead (Z = 82) than copper (Z = 29).
b. Compton Scattering
Compton scattering events is actually not much different from the photoelectric effect. However, not all of the Compton scattering of photons of energy given to electrons, but only partially, the rest is still a photon energy of electromagnetic waves (photons) are scattered. Scattered photons will continue to interact with other electrons until the energy runs out and the resulting electron (photoelectron) will cause secondary ionization processes.
In Compton scattering, photons with energies hλiberinteraksi the outer electrons of atoms, then photons with energies hλodihamburkan and a photoelectron escape from this bondage. Electron kinetic energy (Ee) for the energy difference between incoming photons and outgoing photons.
Ee = hλi-hλo
Compton scattering is dominant occurs when the photon energy has a moderate (above 0.5 MeV) and occurs more frequently in the material with a mass number (Z) is low.
c. Pair production
When in the field of nucleus of an atom, the photon can experience conversion (disappear) into postron elektorn positively charged and negatively charged. By using the conversion equation of energy into mass (E = mc2), electrons and positrons produced will have the energy equivalent of 0.511 MeV. Therefore, only the big-energy photons (> 1.02 MeV) which can produce electron-psoitron. Any excess energy above 1.02 MeV will be given to the particles in the form of kinetic energy. (Total kinetic energy of two particles is equal to the incident photon energy minus 1.02 MeV).
The resulting electron will interact with the surrounding atoms and cause ionization, while the positrons will find a free electron and these two particles will eliminate each other (positron interaction), and produce energy.
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