Question

question 1 (5 points)
in a cathode ray tube, the number of electrons that reach the fluorescent screen is controlled by the
a) anode.
b) cathode.
c) deflecting plate.
d) grid.

Explanation:

Identify the function of each component in a cathode ray tube (CRT)

To determine which component controls the number of electrons reaching the screen, we analyze the role of each option:

• Cathode: Emits electrons via thermionic emission when heated.
• Anode: Accelerates the emitted electrons toward the screen and focuses them into a beam.
• Deflecting plates: Use electric fields (or magnetic fields from coils) to deflect the electron beam horizontally and vertically, controlling where the beam strikes the screen.
• Grid (Control Grid): Positioned between the cathode and the anode, it has a variable negative potential. By adjusting this negative voltage, it regulates the flow (brightness/number) of electrons passing through to the screen.

Determine the correct option

The component that specifically controls the number of electrons (which determines the brightness of the spot on the screen) is the control grid.

Answer:

• (A) anode.
• (B) cathode.
• (C) deflecting plate.
• (D) grid. (Correct answer)