When the filament is heated and electrons are emitted

When the filament is heated and electrons are emitted

• A. Thermionic Emission
• B. Bremsstrahlung
• C. Ionization
• D. Photoelectric Effect

Answer: (A)

Heating a filament supplies enough thermal energy for electrons to overcome the surface barrier and escape into vacuum; this is thermionic emission. In an X-ray tube, these emitted electrons are then accelerated toward the anode to form the electron beam that produces X-rays when they strike the target. The other processes involve different mechanisms: Bremsstrahlung comes from fast electrons decelerating in a material, generating X-rays but not from heating the filament; ionization is the general removal of electrons from atoms by various interactions; the photoelectric effect ejects electrons when photons transfer their energy to the atoms. The scenario described specifically matches thermionic emission because the triggering factor is heat causing electron emission from the filament.

Heating a filament supplies enough thermal energy for electrons to overcome the surface barrier and escape into vacuum; this is thermionic emission. In an X-ray tube, these emitted electrons are then accelerated toward the anode to form the electron beam that produces X-rays when they strike the target. The other processes involve different mechanisms: Bremsstrahlung comes from fast electrons decelerating in a material, generating X-rays but not from heating the filament; ionization is the general removal of electrons from atoms by various interactions; the photoelectric effect ejects electrons when photons transfer their energy to the atoms. The scenario described specifically matches thermionic emission because the triggering factor is heat causing electron emission from the filament.