An electron gun is used with which instrument?

• A. Light microscope
• B. Electron microscope
• C. Fluorescence microscope
• D. Scanning tunneling microscope

Answer: (B)

An electron gun provides the beam of electrons that electron-based imaging instruments use to form images. It emits electrons from a heated filament and accelerates them in a vacuum, creating the high-energy beam required for high-resolution imaging in electron microscopes (both transmission and scanning types). Light-based instruments—like light microscopes and fluorescence microscopes—rely on visible light and emitted photons, so they don’t use an electron gun as their source. The scanning tunneling microscope uses a sharp tip to sense tunneling currents, not a beam of electrons produced by a gun for illumination. So, the instrument that uses an electron gun is the electron microscope.