Which component is responsible for focusing the electron beam toward the anode?

Which component is responsible for focusing the electron beam toward the anode?

• A. Filament
• B. Focusing Cup
• C. Anode
• D. Glass envelope

Answer: (B)

The focusing cup is designed to shape and direct the electron beam toward the anode. It sits around the filament and is held at a negative potential relative to the filament, creating an electrostatic field that repels electrons near the edges and guides them toward the center. This focusing effect counters the natural tendency of the emitted electrons to spread out (space-charge effect), producing a narrow, well-directed beam and a smaller, more precise focal spot on the anode. The filament is merely the source of electrons, the anode is the target that accelerates and collects them, and the glass envelope simply contains the vacuum.

The focusing cup is designed to shape and direct the electron beam toward the anode. It sits around the filament and is held at a negative potential relative to the filament, creating an electrostatic field that repels electrons near the edges and guides them toward the center. This focusing effect counters the natural tendency of the emitted electrons to spread out (space-charge effect), producing a narrow, well-directed beam and a smaller, more precise focal spot on the anode. The filament is merely the source of electrons, the anode is the target that accelerates and collects them, and the glass envelope simply contains the vacuum.