To understand how lasers work we must first understand the physics behind light waves. Light is emitted from a source and travels in straight lines and when it strikes an object is either absorbed, reflected, or refracted. Light behaves primarily like a wave and its this wave nature of light that allows lasers to work. Constructive interference is what amplifies light. Since light is a wave it has a frequency calculated by the equation:

where f is the frequency c is the speed of light which is equal to 3.00 x 108 m/s and is the wave length of light. Also waves have crests, the high points of waves, and troughs, the low points. Constructive interference occurs when two waves of the same frequency meet at a crest or trough therefore combining to form a wave that has an amplitude equal to the sum of the individual amplitudes of the original waves. Stimulated emission is the process that the

The military is one of the most vast areas in which lasers play a key roll. Lasers are used in the military for guidance, defense and detection. Innovations such as a laser guidance unit is used to locate or "paint" a target and provide guidance information to a missile or attack unit. Inversely a laser jamming unit is used to direct energy to a hostile attacker to jam or confuse their radar, guidance, tracking, and other devices. A very commonly known detection system is the laser intrusion detector. This is a thin beam that can be placed in entrances so that when broken will alert an intrusion, this device is also used in many commercial and home based alarm systems. Research is currently being done to develop offensive military weapons a concept that has been in the works since the cold war. In March of 1983 President Ronald Regan first proposed the development of an antiballistic missile defense system to provide the United States total protection from nuclear attack. The goal was to intercept incoming missiles in midcourse. This would require advanced technologies some of which were only in the preliminary stage of research. Given the name "Star Wars" the plan required space and ground-based nuclear X-ray lasers, subatomic particle beams and computer-guided projectiles fired by electromagnetic rail guns. Also a network sensors and specialized mirrors for laser targeting would be required. Some of the systems were in development, but some, particularly the laser systems, were unattainable. The total cost of the system was almost three hundred times more than the departments annual budget.

that is that the frequency can be adjusted by rotating the dye prism inside the laser cavity.

Aside from the many uses of lasers that most people will never see, there are endless uses in our every day lives the most common today is the compact disks. A compact disk is a plastic disk with a thin metallic layer. A high precision laser beam is used to burn microscopic pits in the thin metal layer of the disk called a master disk. The pits are laid out in a pattern that can be read by compact disk player and thousands of disks can be copied off the master. A compact disk player is constructed with a low power laser and high precision lenses and mirrors. A server motor position an objective lense to a track on the disk the laser then directs a narrow beam of light on to the track along the track regions with pits scatter light in different directions. This sequence of light scattering represents sound. A photo detector picks up the light sequence and sends a signal to a microprocessor which then converts the light to sound. This same process can also be used for storing information, animation, and video. Lasers have also simplified the recording of three-dimensional images called holograms. Holograms are made by splitting a beam in to two. One beam will travel through a lense (beam spreader) and then scattered by the object being holographed and be projected on to a film. The other will only travel through a separate lense and then on to the film the two beams interfere with ea

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Approximate Word count = 2098
Approximate Pages = 8 (250 words per page double spaced)