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Saturday, 31 October

JEE Main 2020 · PhysicsMultiple choiceSingle correctMediumMulti-step

JEE Main 9 January 2020, Shift 2, Physics Q18

Question 18 of 75 in this shift, Physics question 18 of 25, Section A.

An electron of mass mm and magnitude of charge ∣e∣|e| initially at rest gets accelerated by a constant electric field EE. The rate of change of de-Broglie wavelength of this electron at time tt ignoring relativistic effects is :
  1. (1)−h∣e∣Et2\frac{-h}{|e|Et^2}Official answer
  2. (2)∣e∣Eth\frac{|e|Et}{h}
  3. (3)−h∣e∣Et-\frac{h}{|e|E\sqrt{t}}
  4. (4)−h∣e∣Et-\frac{h}{|e|Et}

Official answer

Option 1

NTA final key (Jan 2020).

Chapter
Dual Nature of Radiation and Matter
Topic
Matter Waves
Idea tested
Time Rate of Change of Wavelength

Same idea in other shifts

Asked 3× in all
  1. 8 Apr 2025, Shift 2 · Q50An electron is released from rest near an infinite non-conducting sheet of uniform charge density '−σ-\sigma' .The rate of change of…MediumNumerical value
  2. 27 Jul 2022, Shift 1 · Q47An electron (mass m) with an initial velocity v⃗=v0i^\vec{v}=v_0\hat{i} (v0>0v_0>0) is moving in an electric field E⃗=−E0i^\vec{E}=-E_0\hat{i}…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.