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Laser
A laser relies on the property of atoms with excited electrons, which are in a higher energy state than normal, to emit a photon when they fall back to a lower state.
Explanation
If this photon hits an electron in another atom in the same excited state, this electron will also fall back, emitting a photon that is then in phase with the first, producing coherent and monochromatic radiation.
HistoryThe theoretical basis for the laser was first proposed by the German physicist Albert Einstein as early as 1917. The American physicist Joseph Weber submitted a paper on using stimulated emissions in 1951. |