Trends: Industry predictions are that human society will move away from incandescent light bulbs to LED lamps in about a decade or two. People like smaller electricity bills. Environmentalists want less energy wastage as heat. Haitz’s Law states that “every decade, the cost per lumen (unit of useful light emitted) falls by a factor of 10, and the amount of light generated per LED package increases by a factor of 20, for a given wavelength (color) of light.”
Working: We know how light bulbs work. Pass electricity through a tungsten filament. It resists the flow of electrons, becomes warm and radiates heat and light. LEDs are a little more complicated. There is a flash animation at this link which illustrates how they work :http://zeiss-campus.magnet.fsu.edu/tutorials/leddiagram/indexflash.html.
The featured image is from this page. Diodes in general, allow electrons to pass through in only one direction, from the cathode to the anode. Also, their resistance to electron flow depends on the voltage you apply across the their terminals. It’s not linear. Semi-conductor diodes are generally made of silicon. Most diodes are used as “electrical valves” in circuits. Light-Emitting Diodes are made using gallium, arsenic, phosphorous, indium, aluminum, silicon carbide and gallium nitride. Depending on the materials used, different colours (wavelengths) of light are emitted. And depending on the voltage applied across the terminals, different number of photons are emitted. The light emitted by the LED is focused in a single direction using mirrors and lenses. Many LEDs are clustered together for greater light output as well as to generate “white light” by mixing up different colours. Heatsinks are used to dissipate the heat generated by the LEDs. High temperatures not only alter the functioning of the LED lamps but also reduce their life. Now we know why LED lamps are more expensive than tungsten lamps. There is an interesting new development on the horizon called OLED (organic light emitting diode), that needs more time to make it to cost-effective production.
Recycling LED Lamps: CFLs and tube lights which contain mercury must be properly recycled. According to the Iowa Waste Reduction Center, mercury can cause damage to the brain, nervous system, kidney and liver. Tungsten lamps contain both lead and mercury. LED lamps and Tungsten lamps are not currently classed as toxic and find their way into landfills. But tungsten lamps contain both lead and mercury. And LED lamps contain lead and nickel, arsenic, copper, and other metals that have been linked to different cancers, neurological damage, kidney disease, hypertension, skin rashes and other illnesses in humans, and to ecological damage in waterways. (Source) It is a very good idea to find out what recycle options are available in one’s locality for LED lamps. Particularly with the present problems related to waste disposal in Bangalore. This link gives you a list of e-waste recycling centres in bangalore: http://www.weeerecycle.in/e_waste_collection_centres_bangalore.htm.