Which device uses a beam of electrons to reproduce an image on a fluorescent screen?

• A. Cathode ray tube
• B. Oscilloscope
• C. Amplifier tube
• D. PulsER tube

Answer: (A)

A cathode ray tube reproduces an image on a fluorescent screen by firing a focused beam of electrons that is steered across the inner surface of the tube. The heated cathode emits electrons, which are accelerated by high voltage toward the screen. Magnets or electrostatic deflection plates steer the beam so it sweeps across the phosphor-coated screen in a raster pattern. When the beam hits the phosphor, it glows, creating bright points that form the visible image. This scanning electron beam and phosphor interaction is the key idea behind CRT displays, televisions, and older monitors. The other devices served different roles, such as amplifying signals or serving as non-display components, and do not define a display method based on a flying electron beam creating a phosphor image.