Positive rays was discovered by

Which of the following is not the property of a cathode ray

$1$ $J$ is equal to how many electron volt? 

An electron beam is moving between two parallel plates having electric field $1.125 \times {10^{ - 6}}N/m$. A magnetic field $3 \times {10^{ - 10}}T$ is also applied so that beam of electrons do not deflect. The velocity of the electron is ............ $m/s$

A beam of cathode rays is subjected to crossed electric $(E)$ and magnetic fields $(B).$ The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by (where $V$ potential diffrence between kethod and anode)

In a Thomson set-up for the determination of e/m, electrons accelerated by $2.5$ $kV$ enter the region of crossed electric and magnetic fields of strengths $3.6 \times {10^4}V{m^{ - 1}}$ and $1.2 \times {10^{ - 3}}T$ respectively and go through undeflected. The measured value of $e/m$ of the electron is equal to