In physics, specifically statistical mechanics, a population inversion occurs when a system (such as a group of atoms or molecules) exists in a state with more members in an excited state than in lower energy states. The concept is of fundamental importance in laser science because the production of a population inversion is a necessary step in the workings of a standard laser.
Read more about Population Inversion: Boltzmann Distributions and Thermal Equilibrium, The Interaction of Light With Matter, Selection Rules, Creating A Population Inversion, Other Methods of Creating A Population Inversion
Famous quotes containing the word population:
“O for a man who is a man, and, as my neighbor says, has a bone in his back which you cannot pass your hand through! Our statistics are at fault: the population has been returned too large. How many men are there to a square thousand miles in this country? Hardly one.”
—Henry David Thoreau (1817–1862)