An electron of mass ' m ' and charge ' e ' initially at rest gets accelerated by a constant electric field ' E '. The rate of change of de-Broglie wavelength of the electron at time ' t ' is (Ignore relativistic effect) ( h = Planck's constant)

Step-by-step solution

The electron of mass m and charge e is initially at rest in a constant electric field E . The force on the electron is F = eE , producing acceleration a = eE m . With initial velocity zero, the velocity at time t is v = at = eEt m . The de Broglie wavelength is = h mv = h m eEt m = h eEt . Differentiating with respect to time gives the rate of change: d dt = d dt ( h eE t⁻¹ ) = - h eE t⁻² = - h eEt^2 This corresponds to option A .