Problem 3.391

A beam of non-relativistic charged particles moves without deviation through the region of space \(A\) (Fig. 3.103 ) where there are transverse mutually perpendicular electric and magnetic fields with strength \(E\) and induction \(B\). When the magnetic field is switched off, the trace of the beam on the screen \(S\) shifts by \(\Delta x .\) Knowing the distances \(a\) and \(b,\) find the specific charge \(q / m\) of the particles.