What is the function of the anode in an x-ray tube?

• A. The anode emits electrons via thermionic emission.
• B. The anode filters photons to shape the beam.
• C. The anode focuses electrons toward the cathode.
• D. The anode serves as the target for electrons, producing x-rays upon impact and providing a path for current while dissipating heat.

Answer: (D)

In an X-ray tube, the essential role of the anode is to serve as the target that the accelerated electrons strike, producing X-rays, while also completing the electrical circuit and dissipating the heat generated by that interaction. When the cathode thermally emits electrons and a high voltage accelerates them toward the anode, their impact on the anode target (typically tungsten) creates X-rays through both Bremsstrahlung and characteristic processes. The anode must conduct the current and withstand the intense heat, often using a rotating target to spread the thermal load.

This is why the option describing the anode as the target for electrons, where X-rays are produced upon impact and where current flows while heat is dissipated, is the best choice. The other statements mix up roles: emission is done by the cathode, photons are shaped by external filters rather than the anode, and while the electric field can influence electron paths, focusing is mainly accomplished by the cathode’s focusing cup rather than the anode.