At what operating voltage threshold does Characteristic radiation occur in dental x-ray machines?

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Multiple Choice

At what operating voltage threshold does Characteristic radiation occur in dental x-ray machines?

Characteristic radiation arises when the incoming electron has enough energy to eject a K-shell electron from the target atom. When that inner-shell vacancy is filled by an electron from a higher shell, a photon is emitted with energy equal to the difference between those shells—this creates the characteristic X-ray lines specific to the target material. For a tungsten target, the K-shell binding energy is about 69.5 keV, so the incident electron must have at least roughly 70 keV of energy to knock out a K-shell electron. Therefore, characteristic X-rays become detectable when the tube operates at about 70 kV or higher; below that, bremsstrahlung dominates and characteristic emission is minimal. Hence the threshold is around 70 kV and above.

Characteristic radiation arises when the incoming electron has enough energy to eject a K-shell electron from the target atom. When that inner-shell vacancy is filled by an electron from a higher shell, a photon is emitted with energy equal to the difference between those shells—this creates the characteristic X-ray lines specific to the target material. For a tungsten target, the K-shell binding energy is about 69.5 keV, so the incident electron must have at least roughly 70 keV of energy to knock out a K-shell electron. Therefore, characteristic X-rays become detectable when the tube operates at about 70 kV or higher; below that, bremsstrahlung dominates and characteristic emission is minimal. Hence the threshold is around 70 kV and above.

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