A particle of mass m and charge (- q) enters the region

A particle of mass m and charge (- q) enters the region between the two charged plates initially moving along X-axis with speed vx (like particle in figure). The length of plate is L and a uniform electric field E is maintained between the plates. Show that the vertical deflection of the particle at the far edge of the plate is qElIl (2 m${{v}^{2}}$). Compare this motion with motion of a projectile in gravitational field.