Thermions are

The metal which has the highest work function among the following is:

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

When subjected to a transverse electric field,cathode rays move

Which of the following is not true with respect to cathode rays?

What is specific charge? Write its standard value.