The term LASER originated as an acronym for Light Amplification by Stimulated Emission of Radiation.
Absorbing energy excites atoms and molecules. When they are struck by radiation of a suitable frequency, they release their energy as a wave exactly in step with that radiation. Albert Einstein had predicted this stimulated emission in 1917.
In a laser, new radiation strikes other excited atoms, which emit light and lead to a chain reaction. This produces high-intensity radiation with all the waves in step with each other.
Laser light is considered pure because it consists of waves of a single frequency, all in step. Laser can be used in instances when light made of jumbled waves of different frequencies is not enough. It can be extremely intense, allowing us to cut metal using it, and narrower than an ordinary beam of light. Lasers are used to make accurate measurements. Their narrow beam is used in surveying to bounce off distant reflectors and give pinpoint positioning. The content in a CD is read by tiny low-powered infrared lasers. Holograms and light shows also make use of lasers.
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