In a parabola spectrograph, the velocities of four positive ions $P,Q,R$ and $S$ are $v_1$, $v_2$, $v_3$ and $v_4$ respectively

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

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)

The charge on electron was discovered by

A stick of $1 \,m$ is moving with velocity of $2.7 \times {10^8}m{s^{ – 1}}$. ……….. $m$ is the apparent length of the stick  $(c = 3 \times {10^8}m{s^{ – 1}})$