Cathode rays are produced when the pressure is of the order of

The relation between current and charge is given by $I = A T^2 e^{qV / V_L}$. What is the value of $V_L$?

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

The mass of the electron varies with

Explain the emission of electrons from a metal. Define work function. Write its unit,and state the factors upon which the work function of a metal depends.

$A$ metal plate gets heated when cathode rays strike against it due to: