Lasers are the result of electrical energy absorption by electrons within specially-designed glass, crystal or gas, causing the electrons to move to a high-energy rotation around their atomic nucleus before slowing down toÂ emit light particles (or photons). In fact, the clue to how a laser works is encoded within its name, which is an acronym for "light amplification by stimulated emission of radiation."
The light emitted is coherent, which means that it doesn't spread out like regular light but remains in a narrow beam. This is because, unlike ordinary white light, which contains a range of colors, laser light contains just one. As a result, when it comes into contact with another material, all of the light, being of a single wavelength, bends uniformly and therefore does not scatter.
In practice, this means that a laser beam can be emitted over extreme distances without losing its focus.
Because of this unique property of lasers, they are often used when precision is of paramount importance. In construction, for instance, they are used for leveling surfaces. They are also used to measure the distance of the Moon from the Earth. In order to do this, scientists at NASA reflected a laser beam against a mirror that was left there as part of an Apollo mission.