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

Options

A. `(B^2)/(2VE^2)`
B. `(2VB^2)/(E^2)`
C. `(2VE^2)/(B^2)`
D. `(E^2)/(2VB^2)`

Answer

D

Explanation

`Bqv = qE " " ….(i)`
` v = E/B`
` 1/2 mv^2= qv`
`1/2 m (E^2)/(B^2) = qV`
` q/m = (E^2)/(2B^2 V)`