SCIENCE & TECHNOLOGY |
Which CFL to buy?
THIS UNIVERSE
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Which CFL to buy? India is fast waking up to use of energy-efficient lighting. Ever mounting power consumption with demand outstripping supply every year has further made it essential. Time is not far when conventional light bulbs will either see a production ban or their use declared illegal. So save and keep one safe to enjoy a yellow-light dinner sometime or to relive your old romantic days. In Punjab, the PSEB has already launched a strong campaign for use of CFLs. July 1, 2008 onwards, every household has to use at least five CFLs or face penalty. All agricultural consumers are now supposed to install only CFLs in their tubewell rooms. The consumers, however, have nothing to lose in switching over to CFLs. Their own power bills will come down and that is always welcome. Only pain in the throat is the initial cost of CFLs. This can somehow be recovered by making right choice of CFLs. All CFLs (Compact Fluorescent Lamp) are no more the same. Market has a variety of them. For the consumer, cost difference is the only criterion for choice. Otherwise, all look white to him. Well, there are some finer points to consider. ROHS compliance: Not all CFLs are ROHS compliant. Also called Lead free directive, ROHS is a directive that was issued by European Union (EU) in February, 2003 and came into effect on July 1, 2006. It means ‘Restriction of Hazardous Substances’. It restricts use of following six substances in the electric appliances and equipment: 1. Lead 2. Mercury 3. Hexavalent Chromium 4. Cadmium 5. PBB (Poly Brominated Biphenyls) 6. PBDE (Poly Brominated Di-phenyl Ether) These substances are considered as hazardous substances. Last 2 substances are flame retardants and are used in plastics. More and more industries are making their products ROHS compliant in an effort to produce environment-friendly products and also keeping in mind that the directive will soon become universally mandatory. When buying a CFL, look for a ROHS compliant one. ISI Mark: IS 15111 Part 1 & 2 cover the safety and performance requirements of CFLs. These standards cover rated wattage up to 26W and Rated voltage up to 250 volts. An ISI marked CFL will always prove safer and give better performance. So always look for an IS 15111 marked one. Wattage: An 11W CFL gives illumination equivalent to 60W Tungsten filament GLS (General Lighting Service) lamp. A 20W CFL is equivalent to 100W GLS. General formula is that 1 watt of CFL gives illumination equivalent to 5 watts of GLS. So replace your 25W GLS with 5W CFLs, 40W bulbs with 8W CFLs, 60W bulbs with 11W CFLs, 100W lamps with 20 W CFLs and 200W lamps with 36W CFLs. However CFLs are available for 7W, 9W, 13W, 15W, 23W, 26W, 35W, 45W, 65W and 85W also. All these CFLs can be put into the existing brackets. So no problem there. Avoid Liquid Mercury CFLs: Many CFLs are produced by using liquid mercury in them. Such CFLs are cheaper than others. Liquid mercury is harmful to environment. Also, when liquid mercury is used, prescribed ISI norms on weight of CFLs are hard to meet. Disposal of used CFLs that contain Lead or Liquid Mercury is harmful for water and environment. Ways and means are being looked into for safe disposal of CFLs. For the time being, governments are providing incentives like lottery tickets in lieu of used CFLs. So prefer to look for CFLs that are marked ‘liquid mercury free’. Buy Genuine CFLs: Chinese CFLs are available in the market at very cheap rates but the big difference in brightness from genuine CFLs and Chinese CFLs can be realised only by trying each at night. Even 4 Chinese CFLs don’t generate brightness equivalent to one genuine CFL. Life of Chinese CFLs is very short and these develop black spots very soon. Many reputed companies like Havells, Wipro, Philips, Crompton Greaves, Khaitan are producing a wide variety of CFLs in India. CFLs manufactured by these companies should be chosen by looking at the points noted above instead of buying Chinese CFLs. Cost factor: Biggest deterrent behind non-usage of CFLs is their initial cost. However, it is a proven fact that combined with the power saved, these lamps prove much cheaper than conventional lamps. A genuine 11W CFL is priced around Rs 125.00, a 15W CFL at Rs 130.00 and a 20W CFL at Rs 180.00. There are large discounts available on these ranging up to 35 per cent. An 11W CFL should therefore be available at about Rs 80.00. In comparison to a bulb price of Rs 10.00, this looks very high but it is like making an investment to save power. Till the time the country switches over to CFLs, the government should think of making these available at subsidised rates. Otherwise tax free production of CFLs can be allowed to reduce their rates. Once CFLs come under use and their true benefits are realised, there won’t remain need of any such measures. |
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THIS UNIVERSE When it is possible to make one-way see-through glass, why it is not possible to do the same with sound? I beg your pardon if my question sounds naïve or silly. I thank you for asking this question, because it appears to have resulted from original thought and curiosity. Let me see if I can provide a credible answer. Firstly, when we talk of one-way see-through glass, we are thinking about a room with a glass window or wall through which we can see only in one direction. Such rooms are often used for identification of crime suspects. The witness is on one side of the glass while the suspects are in a line-up on the other side. If the suspect’s side of the room is brightly lit and the glass partition is partially silvered, the suspects will not be able to see the witness. The irises of their eyes will narrow while adjusting to the bright light, and the faint light coming through the silvered glass will not be perceptible. On the other hand, the witnesses in the darkened room will be able to clearly see the suspects. That is the one-way-ness of the arrangement. It relies on the fact that in the presence of a large optical signal, our eyes adjust in such a way that lower level signals fall below the perception threshold. We have a familiar example; we do not see stars during the day because the atmospheric window becomes bright. The atmosphere seems to act as a discriminator! The question is whether this kind of discriminatory perception exists for our sense of hearing as well. Eyes and ears may be somewhat different sensing organs, but there is no question that small sounds get easily drowned out when loud music is being played. You may be able to eavesdrop on the conversation of two people from outside the room, but only if there exist no other loud sounds nearby; you will hear much less (or nothing) of their words if a marriage band (or a three-wheeler blaring election propaganda) goes by. In that sense, all rooms are one-way hear-through systems. This is particularly true if the room is partially sound proofed. While loud noises in the veranda would be disturbing to those inside, the soft music playing inside would not be heard or enjoyed by a garrulous crowd outside the room.
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