Indian Forest Service (Mains), Chemistry optional · 2025 · Paper I
Q2(b)(i). Lifetime and spectral uncertainty
Question
The average gap between excitation and emission is 10⁻⁸ s. Calculate uncertainty in (1) energy and (2) frequency. Given h = 6.626 × 10⁻³⁴ J s.
Answer in brief
Using the estimate ΔEΔt ≥ ℏ/2, the minimum estimates are ΔE = 5.27 × 10⁻²⁷ J and Δν = 7.96 × 10⁶ Hz.
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Coversenergy–time uncertaintyHeisenberg uncertainty principleexcited state lifetimenatural linewidth
All parts of Question 2
- 2(a)(i) Hydrogen equation in spherical coordinates10 marks
- 2(a)(ii) Box length from an emission frequency5 marks
- 2(b)(i) Lifetime and spectral uncertainty5 marks
- 2(b)(ii) Dissociation energies of dioxygen species10 marks
- 2(c)(i) Ordering molecular dipoles5 marks
- 2(c)(ii) Bonding and magnetism of B₂5 marks