Thompson's cathode ray tube experiment faced challenges in measuring the charge of a single electron directly, as capturing one electron across the gap and measuring the charge deposited on the anode would have been technically difficult. The method required for such precise measurements was not feasible at the time, as evidenced by Millikan's extensive efforts to determine the electron's charge. Thompson successfully measured the m/q ratio of the electron, but distinguishing whether the small ratio resulted from a low mass or a high charge was not possible without prior knowledge of the charge value, which Millikan had not yet established. The experiment relied on measuring macroscopic quantities, making it easier to derive the m/q ratio compared to attempting to measure individual electrons. Overall, the limitations of technology and methodology at the time hindered direct measurement of a single electron's charge.
