In a modern X-ray tube, electrons are emitted by a filament at the cathode.

• A. Ceramic container under vacuum
• B. High voltage applied across anode and cathode
• C. Majority of e- energy transferred to target as heat while remainder converted to x-rays as e- decelerate
• D. Electrode and cathode, where electrons are emitted by a filament at the cathode

Answer: (C)

When the electrons from the filament hit the target, their kinetic energy is mostly turned into heat in the anode material. Only a small portion of that energy is emitted as X-ray photons through bremsstrahlung and, to a lesser extent, characteristic radiation. That makes sense because the process of stopping high-energy electrons in a dense, high-Z target is far more efficient at heating the material than at producing X-rays. The statement captures this energy partitioning exactly: most of the electron energy becomes heat, while the remainder goes into X-ray production. The other points describe parts of the tube or the emission site but don’t address how the energy actually converts into X-rays versus heat.