this isnt homework, im just doing a bit of revision before exams, and came across this problem. Not really sure where to start really. here it is: In an electron gun of a TV picture tube the electrons (charge -e, mass m) are accelerated by a voltage V. After leaving the electron gun, the electron beam travels a distance D to the screen. In this region there is a transvers magnetic field of maginitude B and no electric field. Show that the approximate deflection of the beam on the screen due to this magnetic field is d = ((BD^2)/2) * (e/2mV)^0.5 where d is the distance from where the beam would hit the screen if it were traveling straight, to where it does hit the screen. any ideas?