Question

A particle having charge + q mass m is released from rest in the region of uniform electric field of magnitude a not at t is equal to zero find its de broglie wavelength as a function of time t

Answer 1

I'm writing this answer assuming you know basics of electrostatics.

Work done = e×V (e - charge on electron, V -  potential difference) 

Since this work is stored in the form of Kinetic energy , 
(0.5)mv² = e×V 

Therefore v = [(2×e×V)÷m]^½

Answer 2

 An electron of mass m and charge e is accelerated from rest through a potential difference v in vacuum. What will its final speed be?