An electron tube in which a beam of electrons from the cathode is used to reproduce an image on a fluorescent screen at the end of the tube is referred to as:

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

Answer: (A)

The key idea is a display that uses a beam of electrons to form an image on a phosphorescent screen. In this tube, electrons are emitted from a heated cathode, accelerated toward the screen, and steered to different positions so the screen glows where the beam hits. The brightness of each spot corresponds to the signal being displayed. Because the image is created this way—by an electron beam from the cathode hitting a fluorescent screen—the device is a cathode ray tube. Other terms describe different vacuum-tube functions or components around the display (such as amplification or beam-sweep functions) but do not define the display device itself.