Bright and Dark Now I have two more questions! First, how does the electron beam move around to different parts of the screen? And second, how do you get gray pictures out of light and dark phosphors? Let me answer these questions one at a time. The current of the electron beam determines the brightness of each phosphor. Voltage between the anode and the cathode can be changed to vary the current of the beam. A higher current means that more electrons hit the screen per second. The higher the current, the brighter the phosphor. That way you can get any shade of gray. Try this!

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