An electron of mass m with an initial velocity v→=v0i^v0>0 enters an electric field E→=-E→0i^  E0= constant >0 ) at t=0. If λ0 is its de-Broglie wavelength initially, then its de- Broglie wavelength at time t is

Here, = λ01+eE0mv0tinitial; velocity v→=v0i^Force action on electron due to electric fieldF→=(-e)-E0i^=eE0i^ Acceleration produced in the electron, a→=F→m=eE0mi^Now, velocity of electron after time tv→t=v→+a→t=v0+eE0tmi^   or   v→t=v0+eE0tm Now, λt=hmvt=hmv0+eE0tm=hmv01+eE0tmv0=λ01+eE0tmv0  ∵λ0=hmv0