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| Sunday, 15 May 2005 |
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Junior Observer |  |
| News Business Features Editorial
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The colourful world of lasers
There are many different types of lasers. The laser medium can be a solid, gas, liquid or semiconductor. Lasers are commonly designated by the type of lasing material employed: * Solid-state lasers have lasing material distributed in a solid matrix. * Gas lasers (helium and helium-neon [HeNe] are the most common gas lasers) have a primary output of visible red light. CO2 lasers emit energy in the far-infrared, and are used for cutting hard materials. * Excimer lasers (the name is derived from the terms excited and dimers) use reactive gases, such as chlorine and fluorine, mixed with inert (inactive) gases such as argon, krypton or xenon. When electrically stimulated, a pseudo (false) molecule (dimer) is produced. When lased, the dimer produces light in the ultraviolet range. * Dye lasers use complex organic dyes, in liquid solution or suspension as lasing media. They are tunable over a broad range of wavelengths. * Semiconductor lasers, sometimes called diode lasers, are not solid-state lasers. These electronic devices are generally very small and use low power. They may be built into larger arrays, such as the writing source in some laser printers or CD players. Laser warning sign Lasers are classified into broad areas, depending on the potential for causing biological damage. It should be labelled with one of these class designations: * Class I - These lasers cannot emit laser radiation at known hazard levels. * Class I.A. - This is a special designation that applies only to lasers that are "not intended for viewing", such as a supermarket laser scanner. The upper power limit of Class I.A. is 4.0 mW.
* Class III A - These are intermediate-power lasers ( 1-5 mW), which are hazardous only for intrabeam viewing. Most pen-like pointing lasers are in this class. * Class III B - These are moderate-power lasers. * Class IV - These are high-power lasers (500 mW), which are hazardous to view under any condition (directly or diffusely scattered), and are a potential fire hazard and a skin hazard. Significant controls are required for Class IV laser facilities. ************ Self-powered marine robot
The Urashima, which is essentially a marine robot, uses an on-board computer to follow a course along a set of pre-programmed coordinates. The design and construction of the vehicle started in 1998, and it completed an underwater cruise of 132.5 kilometres in 2002. Trials over a distance of 220 kilometres, lasting 43 hours, were conducted last year by the Japan Agency for Marine-Earth Science and Technology, which had planned another 300 kilometre cruise. Although it was originally powered by lithium-ion batteries, they were later replaced and in July 2003, the Urashima succeeded in becoming the first vehicle to run underwater with newly developed fuel cells which generate their own power. Further improvements have been made since then.Scientists hope that they will be able to use the vehicle to survey the sea bed in areas prone to earthquake activity. ************** Flexible power
The flexible cell can generate energy even when it is folded or bent. Scientists believe that with the proper development of the technology, solar power generation could be built into clothing, curtains, automobile bodies and many other places. The new cell has a conversion efficiency (the ratio at which solar rays are converted into energy) of 28.5 per cent, double that of the reguar home solar systems. A flexible solar cell weighing a mere gram can generate enough electricity to power a 2.6 Watt bicycle light. This is just one of the countless number of possibilities that the technology offers. |
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| News | Business | Features
| Editorial | Security
| Politics | Produced by Lake House |
We introduced you to lasers recently. Today, we will tell you more
about the colourful world of lasers. 
* Class II - These are low-power visible lasers that emit above Class I
levels but at a radiant power not above 1 mW. The concept is that the
human aversion reaction to bright light will protect a person. 
The Urashima, shown here, is the world's first autonomous underwater
vehicle (AUV) to be powered by fuel cells which generate their own power
underwater. 
A paper-thin solar cell, which has a thickness of about one to three
micrometres (one thousandth of a millimetre) has been developed by Sharp
Corporation. 
