Who discovered the presence of electric charge on an electron?

The mass of a photoelectron is

$A$ beam of cathode rays is subjected to crossed electric $(E)$ and magnetic fields $(B).$ The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by (where $V$ is the potential difference between cathode and anode):

Which scientist invented cathode rays?

Atom or molecules can be visualized by which device or instrument?

The cathode rays have particle nature because of the fact that