Who discovered the ratio of charge to mass of an electron and how? Explain with a diagram.

(N/A) In $1897$,$J.J. Thomson$ determined the ratio of electrical charge $(e)$ to the mass of an electron $(m_e)$ using a cathode ray tube.
The value of the ratio is:
$e / m_e = 1.758820 \times 10^{11} \ C \ kg^{-1}$
Where:
$m_e = \text{mass of the electron in } kg$
$e = \text{magnitude of the charge on the electron in coulomb } (C)$
Method:
$Thomson$ applied electric and magnetic fields perpendicular to each other on the path of the electrons.
Observations:
$1$. When only the electric field is applied,the electrons deviate from their path and hit the fluorescent screen at point $A$.
$2$. When only the magnetic field is applied,the electrons strike the screen at point $C$.
$3$. By carefully balancing the strengths of the electric and magnetic fields,it is possible to bring the electrons back to their original path,hitting the screen at point $B$.
By performing accurate measurements of these deflections,$Thomson$ was able to determine the value of $e / m_e$.