Medium MCQ +4 / -1 PYQ · JEE Mains 2020

An electron of mass m and magnitude of charge |e| initially at rest gets accelerated by a constant electric field E. The rate of change of de-Broglie wavelength of this electron at time t ignoring relativistic effects is :

  1. A ${{ - h} \over {\left| e \right|Et}}$
  2. B ${{ - h} \over {\left| e \right|E\sqrt t }}$
  3. C ${{ - h} \over {\left| e \right|E{t^2}}}$ Correct answer
  4. D ${{\left| e \right|Et} \over h}$

Solution

F = |e| E <br><br>$a = {F \over m}$ = ${{\left| e \right|E} \over m}$ <br><br>V = $at =$ ${{\left| e \right|E} \over m}t$ <br><br>$\lambda$ = ${h \over {mV}}$ = ${h \over {\left| e \right|Et}}$ <br><br>${{d\lambda } \over {dt}}$ = ${{ - h} \over {\left| e \right|E{t^2}}}$

About this question

Subject: Physics · Chapter: Dual Nature of Matter and Radiation · Topic: Photoelectric Effect

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