In the x-ray tube, what is the primary role of the anode?

• A. To emit electrons
• B. To be the target for electrons and produce x-rays
• C. To generate the heating of the filament
• D. To provide vacuum insulation

Answer: (B)

The key idea is that X-ray production happens when high-energy electrons slam into a solid target. The anode serves as that target. When the electron beam from the cathode hits the anode material (usually tungsten), the electrons’ kinetic energy is transformed into X-ray photons, via Bremsstrahlung and sometimes characteristic radiation. A lot of energy also becomes heat, which is why the anode is designed to dissipate that heat—often as a rotating disk to spread the load—but the essential, primary role is to be the target where X-rays are generated.

Emitting electrons is the job of the cathode, not the anode. The heating of the filament is caused by the filament’s own current and handled by the cathode assembly. The tube’s vacuum insulation is provided by the tube envelope and vacuum system, not by the anode.