Thompson's cathode ray tube experiment

Pranav Jha

Why couldn't Thompson just let one electron fly across the gap before disconnecting the battery and turning off the beam, and then measure the amount of charge deposited on the anode,thus allowing him to measure the charge of a single electron directly?

Pranav Jha

also, after Thompson found the m/q ratio of an electron (which was very small compared to that of charged ions in a chemical solution) was there any way by which he could have found out if it was either the mass being too small or the charge being too large which led to the small m/q ratio ( i don't think he could have done so because Millikan hadn't determined the value of "q" by then)

sophiecentaur

That would have been very difficult - and still would be. Can you suggest how he could have measured it? Millikan had enough trouble - months / years of measurements, I believe.
e/m was easier to measure because he 'only' needed to measure macroscopic quantities like radius, volts and a magnetic field.