Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. It is a technique of producing intense beams of light, ultraviolet or infrared radiation of almost a single wavelength. The unique thing about laser radiation is that not only have they the same wavelength, but all the waves travel in phase, like soldiers marching in step. This makes a laser beam so intensely energetic that it can drill a hole, even in diamond, instantly.

A laser works by first pumping energy, in the form of a flash of light, into a collection of atoms, and then forcing the excited atoms to lose energy in the form of light, which appears as a coherent beam. The principle is quite simple. When the atoms in the laser material, which may be a solid, liquid or gas, are excited to a higher state, they can be made to return to the ground state by absorbing radiation of a particular wavelength. This makes a laser beam so intensely energetic that it can drill a hole, even in diamond. In a laser this process goes on till the beam is powerful enough to pass through the half-silvered mirror. The first laser was built in 1960 by an American, Theodore H. Maiman. He used a rod of ruby crystal.

In nuclear reactors a number of radioactive waste products are produced as the fuel is used up. Prominent among them are plutonium, strontium, cesium and barium, which are produced by fission of uranium and neutron irradiation.
There are two types of nuclear wastes: - high-level waste which will be radioactive for thousands of years and low-level waste which is less radioactive. When the fuel elements are first removed from the reactor, they are allowed to cool long enough for the radioactivity of the fission products to decay to acceptable levels, a process usually involving their immersion in water for a month or so. The waste is then sent to nuclear reprocessing plants where useful uranium and plutonium are separated for reuse.
Some low-level waste is pumped straight into the sea. High-level waste is sealed in concrete and steel tanks and stored deep underground. High-level waste is also now being converted to glass. This involves dissolving the spent fuel in acid, converting it into a glassy form, enclosing it in metal containers, and burying it underground. But scientists have not yet found out how to make the rubbish completely safe.Whatever may be the nature of nuclear waste,much dumping of this waste under oceans or seas will cause hindrance to aquatics and will destroy the good nature of sea or ocean

The abbreviation LAN refers to Local Area Network which is nothing but a computer network layering tiny physical area, like office, home, a little group of buildings like school colleges. The noting characteristics of local area network than wide area network is high speed data transfer rates, very little geographic area and need lack for leased telecommunication lines. LAN is the short form of Local Area Network. It allows the linking together of several computers within a building. This interconnection of various computer terminals located in close proximity such as an industrial complex, an office building and a university campus enables each terminal to interact with any other. LAN is, therefore, a multi-user system. Not only is the exchange of data among the various linked up computers made possible by LAN but resourced from a large computer can also be shared. LAN thus offers the most effective means of handling local automated tasks and data management. The ends of the rod were polished flat and silvered, one end being half-silvered to allow the beam to come out. Now a variety of lasers have been made from solids like the ruby crystal and semi-conducting materials, liquids, and gases which produce beams of different colors having different energies.

LAN can be even linked with an outside computer network using ‘gateway’. The gateway converts the formats of data to make them compatible to the two networks.