Q 12-11-141JEE MainJEE Main 2020 (9 Jan, Shift 2)Easy
An electron of mass $m$ and magnitude of charge $e$ at rest, gets accelerated by a constant electric field $E$. The rate of change of de-Broglie wavelength of this electron at a time $t$ is (ignore relativistic effects)
Answer: (D) $\dfrac{d\lambda}{dt} = -\dfrac{h}{eEt^2}$
Momentum grows linearly: $p = eEt$. So $\lambda = \dfrac{h}{p} = \dfrac{h}{eEt}$ and
$$\frac{d\lambda}{dt} = -\frac{h}{eEt^2}$$
Solution by Sreeraj P, M.Sc Physics