Beer-Lambert law integrates Lambert observation that absorbance proportional to path length and Beer observation proportional to concentration. Resulting expression equates absorbance to product of molar absorptivity ε reflecting transition probability, molar concentration c and path length l in centimeters. Mathematically A = log10(I0/I) = ε c l, valid under dilute, non-scattering, monochromatic light conditions. Deviation occurs at high concentration, polychromatic radiation or scattering. This fundamental equation underlies spectrophotometric determination of proteins, nucleic acids, NADH k
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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.