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Question
The energy of a photon of a characteristic X-ray from a Coolidge tube comes from
Options
the kinetic energy of the striking electron
the kinetic energy of the free electrons of the target
the kinetic energy of the ions of the target
an atomic transition in the target
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Solution
an atomic transition in the target
In an X-ray tube, electrons are emitted by the filament. These electrons are made to strike the filament by applying an electric field between the filament and the target. As a result of it, the kinetic energy of the electrons is lost to the target atoms. This energy is utilised by the target atoms to knock out an electron from the innermost shell. Consequently, the electron makes a transition from the higher energy state to this vacant shell. Due to this transition, the difference of energy of the two states gives photon of characteristic X-ray.
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