In an electron gun the control grid is given a negative potential relative to cathode in order to
Decelerate electrons
Repel electrons and thus to control the number of electrons passing through it
To select electrons of same velocity and to converge them along the axis
To decrease the kinetic energy of electrons8.
An electron is moving with constant velocity along $x - $ axis. If a uniform electric field is applied along $y - $ axis, then its path in the $x - y$ plane will be
An electron is accelerated through a potential difference of $200$ volts. If $e/m$ for the electron be $1.6 \times {10^{11}}$ $coulomb/kg$ , the velocity acquired by the electron will be
In Thomson's experiment if the value of $q/m$ is the same for all positive ions striking the photographic plate, then the trace would be
When electron beam passes through an electric field, they gain kinetic energy. If the same beam passes through magnetic field, then
Kinetic energy of emitted cathode rays is dependent on