In Bragg’s Law, nλ = 2d sinθ, what is λ?
In Bragg's equation nλ = 2d sinθ, λ denotes wavelength of incident X-ray radiation illuminating the crystal. Common laboratory sources use copper Kα emission at 1.5418 angstroms, while synchrotron beamlines provide tunable 0.7 to 2.0 angstroms to optimize anomalous signal. Path difference between waves scattered by adjacent lattice planes equals 2d sinθ; constructive interference occurs when this difference equals integer multiple n of wavelength λ. Precise knowledge of λ is therefore essential for resolution calculation, lattice parameter determination and conversion of angular measurements into interatomic distances during data processing.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.