The term laser stands for “light amplification by stimulated emission of radiation”. A laser produces a very thin but very powerful beam of light, so powerful that it can drill a hole through the hardest substance – diamond. Unlike the light from a torch or a fluorescent tube, a laser beam does not spread much. Laser light contains light of only one colour, unlike sunlight which is a mixture of seven colours. Laser beams are highly monochromatic and coherent. The density of their energy also remains the same even over long distances. If comparisons can be made, ordinary light is like a crowd while the laser light is a well ordered army platoon.
The first laser was made in 1960 by an American scientist named Theodore H. Maiman. It was a ruby laser which produced a red beam of light, million times brighter than the sunlight. Today we have different types of lasers which produce different wave-lengths of different powers. Some of the well-known lasers are Ruby, Nel, Yah, He-Ne, Argon, Diode laser etc. A laser has three main parts. They are (1) the medium – the material that produces the beam (such as a ruby crystal or a gas); (2) the power source that energizes the medium and; (3) the resonator to make the beam more powerful (usually mirrors that reflect the light backwards and forwards to build up its strength).
Lasers are used by doctors to perform delicate surgeries, such as re-attaching a detached retina of the eye. The laser treatment is painless and the patient remains conscious during the operation. Laser beams are being used in the treatment of cancer and to stop tooth decay. A laser can be used by a surveyor as an infinitely tall ‘ranging pole’, from which to take bearings and measurements. The laser beam is fired vertically into the sky, and it provides an easily detected fixed point for other surveyors, even if hills and forests are in the way. Builders of skyscrapers use laser beams like plumb-lines to check that the building is vertical. Unlike an ordinary plumb-line, a laser beam cannot be blown by the wind. Because the laser beam is so straight and narrow that it makes an excellent measuring instrument for astronomers. The Apollo astronauts who landed on the Moon in 1969 left behind a laser reflector. Laser pulses were sending from the Earth to hit the reflector, and the beam bounced between the Earth and the Moon accurate to within 15 cms.
Laser beams are used by soldiers as range-finders, target designators, and guided missiles. Experiments are being conducted with lasers as space weapons, for destroying satellites and ballistic missiles.
Lasers are also being used in several fields of research such as Roman effect and interferometry. Lasers are being used in communications, computers, welding and drilling of metals, photography, stone removal from kidneys without operation, heart surgery, meteoreology etc.
