Which of the following has the highest specific charge?

$A$ cathode emits $1.8 \times 10^{14}$ electrons per second when heated. When $400 \ V$ is applied to the anode,all the emitted electrons reach the anode. The charge on an electron is $1.6 \times 10^{-19} \ C$. The maximum anode current is ............ $\mu A$.

Cathode rays enter into a uniform magnetic field perpendicular to the direction of the field. In the magnetic field,their path will be:

Cathode rays are....

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 $3.6 \times 10^4 \ Vm^{-1}$ and $1.2 \times 10^{-3} \ T$ respectively and go through undeflected. The measured value of $e/m$ of the electron is equal to

In the phenomenon of electric discharge through gases at low pressure,the coloured glow in the tube appears as a result of
[$AIPMT$ $2008$]