Which pairing correctly matches x-ray tube components to their primary function?

Which pairing correctly matches x-ray tube components to their primary function?

• A. Cathode — Source of free electrons
• B. Anode — Insulator of vacuum
• C. Glass envelope — Source of x-rays
• D. Focusing cup — Source of photons

Answer: (A)

In an X-ray tube, electrons originate at the cathode through thermionic emission when it’s heated, creating a source of free electrons that form the beam. These electrons are pulled toward the anode by the high voltage and strike the target, producing x-rays. The anode’s primary role is to serve as the target and to accelerate the electrons, not to insulate the vacuum. The glass envelope simply maintains the vacuum around the internals; it isn’t a source of x-rays. The focusing cup helps direct the electron beam to a small focal spot on the target, but it does not emit photons. Because of this, identifying the cathode as the source of free electrons best captures its essential function in x-ray generation.

In an X-ray tube, electrons originate at the cathode through thermionic emission when it’s heated, creating a source of free electrons that form the beam. These electrons are pulled toward the anode by the high voltage and strike the target, producing x-rays. The anode’s primary role is to serve as the target and to accelerate the electrons, not to insulate the vacuum. The glass envelope simply maintains the vacuum around the internals; it isn’t a source of x-rays. The focusing cup helps direct the electron beam to a small focal spot on the target, but it does not emit photons. Because of this, identifying the cathode as the source of free electrons best captures its essential function in x-ray generation.