In a cathode ray tube the length of deflection plates is `78 mm` and their separation is `0.24 m`, while the distance form the centre orf the plate to the screen is `0.33 m`. No deflection of the electron beam is observed when the potential difference is `2800 V` and the magnitude field is `8.2xx10^(-4) Wb m^(-2)`. When only the magnetic field is applied, deflection on the screen is `28 mm`. Find `e//m`.

Answer

`1.59 xx 10^(11) C kg^(-1)`