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Indian Forest Service (Mains)

Chemistry optional

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

Paper I covers physical and inorganic chemistry.

Indian Forest Service (Mains), Chemistry optional · 2025 · Paper I

Q3(a)(i). BCC edge length from diffraction

Question

A BCC solid gives a first-order X-ray reflection (λ = 0.154 nm) from (200) at 16.1°. Calculate the cell edge. Given sin 16.1° = 0.2773.

Answer in brief

The cell edge is 0.5554 nm.

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Topic notes: crystal systems, Bragg's law, X-ray diffraction and radius ratio, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversBragg's lawBCC latticeinterplanar spacing d_hklMiller indicesX-ray diffraction

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