Problem 3.213

A gas is ionized in the immediate vicinity of the surface of plane electrode 1 (Fig. 3.58 ) separated from electrode 2 by a distance $l .$ An alternating voltage varying with time $t$ as $V=V_{0} \sin \omega t$ is applied to the electrodes. On decreasing the frequency $\omega$ it was observed that the galvanometer $G$ indicates a current only at $\omega<\omega_{0}$, where $\omega_{0}$ is a certain cut-off frequency. Find the mobility of ions reaching electrode 2 under these conditions.