Learn

Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumConceptual

JEE Main 31 August 2021, Shift 2, Physics Q19

Question 19 of 90 in this shift, Physics question 19 of 30, Section A.

Consider two separate ideal gases of electrons and protons having same number of particles. The temperature of both the gases are same. The ratio of the uncertainty in determining the position of an electron to that of a proton is proportional to :
  1. (1)memp\sqrt{\frac{m_e}{m_p}}
  2. (2)mpme\frac{m_p}{m_e}
  3. (3)mpme\sqrt{\frac{m_p}{m_e}}Official answer
  4. (4)(mpme)3/2\left(\frac{m_p}{m_e}\right)^{3/2}

Official answer

Option 3

NTA final key.

Chapter
Dual Nature of Radiation and Matter
Topic
Matter Waves
Idea tested
Wavelength Uncertainty via Heisenberg

Same topic in other shifts

All Matter Waves questions
  1. 4 Apr 2026, Shift 2 · Q44The de Broglie wavelength associated with an electron accelerated through a potential difference V is λe\lambda_e and the de Broglie…EasySingle correct
  2. 5 Apr 2026, Shift 1 · Q35An electron of mass mm is moving in an electric field E⃗=−2E0i^\vec{E} = -2E_0\hat{i} (E0E_0 = constant >0> 0), with an initial velocity…MediumSingle correct
  3. 5 Apr 2026, Shift 2 · Q43An electron is travelling with a velocity vv in free space and when it enters a medium, its velocity is reduced by 20%. The de Broglie…EasySingle correct
  4. 6 Apr 2026, Shift 2 · Q47The de Broglie wavelength for an electron accelerated through the potential difference of V1V_1 volt is λ1\lambda_1. When the potential…EasyNumerical value
  5. 2 Apr 2025, Shift 2 · Q33An electron with mass mm with an initial velocity (t=0)(t=0) v⃗=v0i^\vec{v} = v_0\hat{i} (v0>0)(v_0 > 0) enters a magnetic field…MediumSingle correct
  6. 7 Apr 2025, Shift 2 · Q43A photoemissive substance is illuminated with a radiation of wavelength λi\lambda_i so that it releases electrons with de-Broglie…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.