An electron (mass ) with initial velocity is in an electric field, . If is initial de-Broglie wavelength of electron, its de-Broglie wavelength at time is given by
Step 1. Given data:
Initial velocity,
Electric field,
Step 2. The momentum of an electron:
Initially,
STEP 3. Velocity as a function of time =
Because only force is acting in .
So velocity will be changed in and kept constant in .
Step 4. To calculate the wavelength:
Hence, the correct option is (A).