Which statement describes the cathode in an X-ray tube?

Which statement describes the cathode in an X-ray tube?

• A. Heats Up and Creates Electrons
• B. Heats Up and Creates Positive Ions
• C. It Is Positively Charged
• D. It Absorbs Photons

Answer: (A)

The key idea is thermionic emission: the cathode serves as the electron source by being heated so electrons are released into the tube. When the filament is heated, electrons gain enough energy to overcome the metal’s work function and are emitted, forming the electron beam that travels to the positively charged anode to produce X-rays upon impact. That’s why describing the cathode as heating up and creating electrons is the correct choice. The cathode isn’t meant to create positive ions, isn’t positively charged relative to the anode in its role (it’s the source of electrons, not a positive sink), and it doesn’t absorb photons as its primary function.

The key idea is thermionic emission: the cathode serves as the electron source by being heated so electrons are released into the tube. When the filament is heated, electrons gain enough energy to overcome the metal’s work function and are emitted, forming the electron beam that travels to the positively charged anode to produce X-rays upon impact. That’s why describing the cathode as heating up and creating electrons is the correct choice. The cathode isn’t meant to create positive ions, isn’t positively charged relative to the anode in its role (it’s the source of electrons, not a positive sink), and it doesn’t absorb photons as its primary function.