Which means of x-ray production involves projectile electrons knocking out inner shell electrons of tungsten?

• A. Bremsstrahlung
• B. Compton
• C. Photoelectric
• D. Characteristic

Answer: (D)

Characteristic X-rays arise when a fast projectile electron ejects an inner-shell electron from the tungsten atom, creating a vacancy. An electron from a higher shell then fills the vacancy, and the energy difference is emitted as a photon with a specific, characteristic energy. This line emission is unique to the target element (tungsten) and results in a discrete spectrum. This mechanism is distinct from Bremsstrahlung, which comes from deceleration in the nucleus’ electric field and produces a continuous spectrum; from Compton scattering, which is the scattering of X-ray photons by electrons; and from the photoelectric effect, which involves photon absorption, not projectile-electron ionization.