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UPSC Civil Services (Mains)

Chemistry optional

  • 2 papers
  • 250 marks each
  • 3 h per paper
  • 5 of 8 questions, Q1 and Q5 compulsory

Paper I covers physical and inorganic chemistry.

UPSC Civil Services (Mains), Chemistry optional · 2025 · Paper I

Q2(a). Particle in a box: probability in the first quarter

Question

Find the probability of existence of a particle in a one-dimensional box of length ‘a’ in the region 0 ≤ x ≤ a/4 for the states n = 1, 2 and 3.

Answer in brief

P₁ = 0.091, P₂ = 0.250, P₃ = 0.303.

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The full model answer

As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.

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Coversparticle in a one-dimensional boxBorn interpretationprobability densitycorrespondence principlewavefunction normalisation

All parts of Question 2