(2011? Hangzhou model) electrostatic lens is the use of electrostatic fields to make the electron beam convergence or divergence of a device, which a part of the distribution of electrostatic field as

(2011? Hangzhou model) electrostatic lens is the use of electrostatic fields to make the electron beam convergence or divergence of a device, which a part of the distribution of electrostatic field as shown in Fig. Solution: as shown in the figure on the right, we discuss the x-axis above the electron, now take the x-axis above a point P for the object of study.

Because the potential of the equipotential line increases along the x-axis, the equipotential line is perpendicular to the electric field lines, so you can make the electric field lines through the P point, as shown in the figure.

The electron is subject to the electric field force and field strength in the opposite direction, so the electron is subject to a diagonal to the right of the electric field force, so along the y-negative direction of accelerated motion.

The electron passes through the y-axis and is subjected to an electric field force slanting to the upper right, so it decelerates along the y-axis in the negative direction, and accelerates upward if the electron incident velocity is appropriate.

The motion of the electron below the x-axis is symmetrical to that above the x-axis.

So it is possible to converge and then diverge.

C is correct.

So choose C.

This is correct.