cse • paper_1 • waves_oscillations
[UPSC CSE 2008] Polarisation and Modern Optics (Q421, 20M)
Consider an ensemble of two-level atoms in thermal equilibrium. Show that the ratio of Einstein A and B coefficients is given by \frac{A}{B} = \frac{8\pi h \nu^3}{c^3}. Why is it not possible to achieve inversion of population in a two-level medium ?
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