Laser (noun, “LAY-zer”)
This is a device that uses an electrical current to excite the atoms in a liquid, crystal or gas. The atoms contain negatively charged particles called electrons. When they are excited, the electrons move from a low energy state to a higher energy state. But they can’t stay that way very long. They drop down again to that lower energy state. In the process, they give off a blip of light.
The light given off is all the same wavelength. This means we perceive the laser as having a single color, such as green or red. And because the photons are all the same wavelength, that laser light can travel very long distances in a tight, narrow beam.
When the first laser was built in 1960, it wasn’t called a laser at all! “Laser” is an acronym — a word made by combining the starting letters or groups of letters from several words. Originally, LASER was shorthand for “Light Amplification by Stimulated Emission of Radiation.” But over time, the devices have become so popular that “laser” has become its own word.
Lasers are used in everything from medicine to archeology to physics. And of course, they are in those tiny laser pointers we use to play with our pets.
In a sentence
Scientists have used lasers to create maps of an ancient Mayan city.
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