DK Science: Lasers
Some beams of light are powerful enough to cut through metal. Others are precise enough to use for delicate surgery on people’s bodies. These remarkable forms of light are made by lasers. Laser stands for Light Amplification by Stimulated Emission of Radiation. A laser is a device that concentrates light rays so they all travel exactly in step. Laser rays are much more powerful and precise than other light rays.
A laser makes light by passing electricity through a gas. This makes the gas emit (give out) light waves at a precise wavelength. The light waves bounce back and forth along a tube between two mirrors. This encourages the gas to give out more light exactly in step with the original light waves. It also amplifies (makes brighter) the beam of light.
A three-dimensional photograph that seems to hover inside a piece of plastic or glass is called a hologram. Although the hologram appears to be a solid object, it is actually an image that was stored in the plastic or glass by scanning a laser beam over the object.
Some lasers are so powerful that they can shine great distances into the sky. They are often used at rock concerts or to provide spectacular light shows in the open air. This light show is held regularly near the pyramids at Giza in Egypt. Several powerful, computer-controlled lasers produce strong beams of red light that reach up and sweep through the air.
