VKC ScienceChemistry for written exams Telegram

UPSC Combined Geo-Scientist

Chemist

  • 3 descriptive papers
  • 200 marks each
  • 3 h per paper

Mains Paper III covers analytical and organic chemistry.

UPSC Combined Geo-Scientist, Mains · 2024 · Mains Paper III

Q5(b)(i). Wavelength of the sodium resonance line

Question

Calculate the wavelength of the resonance line of sodium atom, if the excitation energy of the resonance level is 2.10 eV. [Given: hc = 12330]

Answer in brief

λ = hc/E = 12 330/2.10 = 5871 Å = 587.1 nm: the yellow sodium D line.

Part of VKC Basic

Read the key points and the full model answer with VKC Basic

VKC Basic (₹999 for 6 months) opens every solved answer, the notes, the handbook and the daily answer archive. Every Mains test series includes it.

See what is included Already a member? Sign in

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.

The handwritten model answer pages open with the VKC plan.
Read the whole 2024 solution2024 question paper

Topic notes: spectroscopic instruments (Beer–Lambert law, UV–vis and IR instruments, Job's method, AAS and flame emission), with every Civil Services, IFoS and Geo-Scientist PYQ →

Coversresonance linesodium D lineE = hc/λflame photometryatomic emission

All parts of Question 5