Which statement accurately describes the cathode in an x-ray tube?

Which statement accurately describes the cathode in an x-ray tube?

• A. It is positively charged and contains the target; it emits electrons from a heated filament
• B. It is negatively charged, contains the small/large filaments within a focusing cup
• C. It accelerates electrons toward the anode
• D. It is the device that measures exposure

Answer: (B)

The cathode is the negative electrode of an x‑ray tube. It contains heated filaments (the small and large ones) inside a focusing cup. When the filament is heated, electrons are emitted from its surface—a process called thermionic emission—and the focusing cup helps shape and direct that electron cloud toward the anode. The high voltage pulls these electrons across the tube toward the positively charged anode, where their collisions with the target produce x-rays. The device that measures exposure is separate equipment, not part of the cathode.

The cathode is the negative electrode of an x‑ray tube. It contains heated filaments (the small and large ones) inside a focusing cup. When the filament is heated, electrons are emitted from its surface—a process called thermionic emission—and the focusing cup helps shape and direct that electron cloud toward the anode. The high voltage pulls these electrons across the tube toward the positively charged anode, where their collisions with the target produce x-rays. The device that measures exposure is separate equipment, not part of the cathode.