Which of the following have highest specific charge
Positron
Proton
$He$
None of these
In Millikan's experiment for the determination of the charge on the electron, the reason for using the oil is
The mass of a particle is $400$ times than that of an electron and the charge is double. The particle is accelerated by $5 V$. Initially the particle remained in rest, then its final kinetic energy will be ........... $eV$
Cathode rays consist of
The cathode rays have particle nature because of the fact that
Cathode rays are produced when the pressure is of the order of