Weaving With Light

共享题干题【2011年真题】（一） Weaving With Light
      In the Sierra Madre mountain range of west central Mexico，the native Huichol people live much the way their ancestors did-without electricity．That's because it's too expensive to string power lines to the remote mountain areas where they live．To help support themselves，the Huichol create beautiful artwork．They sell their art in cities hundreds of miles away from their villages．And without electricity-at home or on the road，they can only work during daylight hours. When it gets dark，they must stop whatever they're doing．
      Now，a team of scientists，designers，and architects is using new technologies to provide the Huichol with light after the sun sets．The scientists' technique involves weaving tiny electronic crystals into fabrics that can be made into clothes，bags，or other items．
      By collecting the sun's energy during the day，these lightweight fabrics provide bright white light at night．Their inventors have named the fabrics"Portable （轻便的）Lights．"Portable Lights have the potential to transform the lives of people without electricity around the world，says project leader Sheila Kennedy．
     "Our invention，"Kennedy says，"came from seeing how we could transform technology we saw every day in the United States and move it into new markets for people who didn't have a lot of money．"
      At the core of Portable Light technology are devices called high-brightness light-emitting diodes （高亮度发光二极管），or HB LEDs. These tiny lights appear in digital clocks，televisions，and streetlights．
     LEDs are completely different from the light bulbs （灯泡）．Most of those glass bulbs belong to a type called incandescent lights （白炽灯）．Inside，electricity heats a metal coil （线圈）to about 2，200 degrees Celsius．At that temperature，bulbs give off light we can see．
    Ninety percent of energy produced by incandescent lights，however，is heat-and invisible. With all that wasted energy，bulbs bum out quickly．They are also easily broken．
     LEDs，on the other hand，are like tiny pieces of rock made up of molecules （分子）that are arranged in a crystal structure．When an electric current passes through an LED，the crystal structure produces light．Unlike incandescent bulbs，they can produce light of various colors．Within an LED，the type of molecules and their particular arrangement determines what color is produced．