When the electrons leave the electrostatic field, they will take a straight path to the screen at the
angle at which they left the field. Because they were all deflected equally, the electrons will be traveling
toward the same spot. Of course, the proper voltages must exist on the anodes to produce the electrostatic
field. Changing these voltages changes the focal point of the beam and causes the electron beam to strike
the CRT at a different point.
Factors Influencing Deflection
The ANGLE OF DEFLECTION (the angle the outgoing electron beam makes with the CRT center
line axis between the plates) depends on the following factors:
Length of the deflection field;
Spacing between the deflection plates;
The difference of potential between the plates; and
The accelerating voltage on the second anode.
LENGTH OF DEFLECTION FIELD.As shown in figure 6-3, a long field (long deflection
plates) has more time to exert its deflecting forces on an electron beam than does a shorter field (short
deflection plates). Therefore, the longer deflection plates can bend the beam to a greater deflection angle.
Figure 6-3.Factors influencing length of field.
Q-5. What effect do longer deflection plates have on the electron beam?
SPACING BETWEEN PLATES.As shown in figure 6-4, the closer together the plates, the more
effect the electric force has on the deflection angle of the electron beam.