heat

Exact electron position is never known. Probability densities are used to visualize trends. In simple terms, energy can be absorbed by an atom. When this happens, electrons store the energy in the form of expanded orbitals. When enough energy is absorbed, the outermost electrons can fly off. Various energy levels exist. When an atom drops from a high-energy level to a lower-energy level, the energy-release may take the form of an emitted photon.

Because electrons repell one-another, atoms that are packed tightly tend to synchronize. Energy is gradually handed-off, from one atom to the next, through this coupling mechanism. Heat is thus conducted from atom to atom as though by bucket-brigade.

LASERs consume pump-energy to excite atoms. Some atoms are continually reaching the highest state, or energy level. Sometimes a stray photon tickles an energized atom in passing. This would kick the energy-level upward again. But there's no higher state to reach. Instead, pent-up energy bursts fourth, emitted in the form of a new photon. Loss of stored energy returns the atom to the ground-state. The new photon emerges in lockstep with the original. Both photons proceed further, perhaps to stimulate more emission. Each interaction can add another photon. The sequence forms a chain reaction. Thus we derive the acronim: Light Amplification through Stimulated Emission of Radiation (LASER). Mirrors are sometimes added, forming an oscillator. When this is done, partial silvering or cavity-dumping can deliver usefull output.

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