Question

An electron of mass m and charge e initially at rest gets accelerated by a constant electric field E. The negative rate of change of De-Broglie wavelength of this electron at time t is–

• A. $\frac{2h}{eEt^{2}}$
• B. –$\frac{2h}{eEt^{2}}$
• C. $\frac{h}{eEt^{2}}$
• D. –$\frac{h}{eEt^{2}}$

Answer 1

Answer: (D)

–$\frac{h}{eEt^{2}}$

Answer 2

l =$\frac{h}{mv}$ Ž v = at Ž v =$\frac{eEt}{m}$

l = $\frac{h}{mv}$= $\frac{h}{eEt}$ Ž $\frac{d\lambda}{dt}$= –$\frac{h}{eEt^{2}}$