At this point, you have a bright spot in the center of the CRT screen as shown in figure 2-22. Having
watched TV, you know that a TV picture consists of more than just a bright spot in the center of the
picture tube. Obviously, something is necessary to produce the picture. That something is called
DEFLECTION. For the CRT to work properly, the spot must be moved to various positions on the
screen. In your TV set for example, the spot is moved horizontally across the CRT face to form a series of
tightly packed lines. As each line is displayed, or traced, the electron beam is moved vertically to trace the
next line as shown in figure 2-23. This process starts at the top of the tube and ends when the last line is
traced at the bottom of the CRT screen. Because the beam is swept very quickly across the CRT and the
phosphor continues to glow for a short time after the beam has moved on, you do not see a series of lines,
but a continuous picture.
Figure 2-22.Impact of an electron beam on a CRT screen.
Figure 2-23.Deflection of an electron beam across a TV screen.