The source of electrons in the x-ray tube is produced by which process?

The source of electrons in the x-ray tube is produced by which process?

• A. Photoelectric emission
• B. Bremsstrahlung
• C. Thermionic emission
• D. Compton scattering

Answer: (C)

Thermionic emission is the process that provides the electrons for an x-ray tube. When the filament is heated by an electric current, its atoms gain enough energy for electrons to overcome the metal’s work function and be released into the vacuum. These emitted electrons form the cathode current and are then accelerated toward the anode by the applied tube voltage, producing x-rays when they strike the target. Other options don’t describe how electrons originate in the tube: photoelectric emission would require photons to eject electrons from a material, Compton scattering involves photon interactions that eject electrons but is a later interaction in the x-ray process, and bremsstrahlung refers to radiation produced as electrons decelerate in the target, not the source of the electrons themselves.

Thermionic emission is the process that provides the electrons for an x-ray tube. When the filament is heated by an electric current, its atoms gain enough energy for electrons to overcome the metal’s work function and be released into the vacuum. These emitted electrons form the cathode current and are then accelerated toward the anode by the applied tube voltage, producing x-rays when they strike the target.

Other options don’t describe how electrons originate in the tube: photoelectric emission would require photons to eject electrons from a material, Compton scattering involves photon interactions that eject electrons but is a later interaction in the x-ray process, and bremsstrahlung refers to radiation produced as electrons decelerate in the target, not the source of the electrons themselves.