Laser light can be made extremely intense, highly directional, and very pure in color.

Light can be characterized both by its frequency, or number of wave crests passing a given point per second, and by its wavelength. Different wavelengths of light are seen as different colors. Like radio waves, light can also carry information. The information in the beam varies in the frequency or shape of the light wave. Because light waves are of much higher

frequencies than radio waves, the have a higher information carrying capacity. In beams of light,individual photon waves are not moving along together because they are not being emitted at the same instant but instead in random short bursts. Such beams are called incoherent.

The process for laser action, was first proposed by Albert Einstein in 1917. The working principles of lasers were outlined

atoms. Light traveling in other directions are soon lost. Some light reaching the output mirror is transmitted to form the laser beam, some is reflected back through the medium to continue the stimulated-emission process.

trillionths of a second. Lasers have been used by car manufacturers to measure wind speed to test the wind resistance of a new car design. A laser beam provides a straight line over a very long distance to help guide engineers when they are digging tunnels. Laser beams were used for alignment in the construction of the Bay Area Rapid Transit system in San Francisco.

matter, instantly vaporizing the plaque. A laser in eye surgery could be used to spot-weld a detached retina. Today lasers make it easier to perform surgical operations that once were considered too dangerous. Dentists also use the red aiming beam of a laser in vaporizing the decayed area of a tooth. The endless uses of lasers in all kinds of medicine is unimaginable.

Lasers are used for monitoring crustal movements and for geological surveys. They are also the most effective detectors of certain types of air pollution. Lasers have been used for precise determination of the earth -moon distance and in tests of relativity. With lasers, the speed of light has been determined accurately, chemical reactions can be selectively induced,

Intense, narrow beams of laser light can cut certain tissues in a small fraction of a second without damaging the surrounding healthy tissues. They have been used to "weld" the retina, bore holes in the skull, vaporize lesions, and clear blood vessels. When arteries are clogged the blood is not flowing through freely. A thin fiber is inserted into the blood vessel to give the

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Approximate Word count = 1164
Approximate Pages = 5 (250 words per page double spaced)