Initial velocity of electron,
v=v0i^+v0j^⇒∣u∣=v02+v02=v02
Initial de Broglie wavelength associated with electron,
λ0=ph=mv02h
now,
v=u+at
Velocity as a function of time =v0i^+v0j^+meE0tk^
so wavelength λ=m2v02+m2e2E02t2h
λ=1+2m2v02e2E02t2λ0