C A light emitting diode , or L．E．D．, is a device that shines when electricity p

C

A light emitting diode （发光二极管）, or L．E．D．, is a device that shines when electricity passes through it．But it works differently thantraditional kinds of light bulbs．Light emitting diodes use less energy and last much longer thanbulbs with a filament （灯丝） inside．L．E．                              D．’s are alsocooler to the touch, and shine a lot brighter than they used to．  

Red L．E．D．’s have long been used assignal lights on electronic equipment．But now light emitting diodes also come in blue and other colors．Colored L．E．D．’s are used to show images on everything from wireless phones tohuge video signs．Andwhite L．E．D．’s are being used increasingly to replacetraditional lighting systems．  

But all these require electricity．In poor countries, people oftenburn fuel to produce light．But the smoke can make people sick．So an electrical engineering professor from Canadastarted a project to produce L．E．      D．lighting systemsfor the developing world．These lights are powered by batteries that can be recharged withenergy from the sun．The batteries can also be charged through other ways, such as windpower and water power．

Professor David Irvine-Halliday tells thestory of how he got the idea．In 1997, while climbing in the Annapurna mountains in Nepal, he sawa small school．Allthe children were outside．He looked through a window and saw that inside the school was dark．The school had a sign thatread: "We have no teachers．If you want to stay and teach for a few days, we would be verypleased．"Professor Irvine-Halliday says that experience had a big effect on him．Back at the University ofCalgary, he was on the Internet one day．He saw a company in Japan selling bright white L．E．                          D．’s．So he built a light with some．This is how he began the LightUp the World Foundation．

48．Compared with traditional kinds of light bulbs, L．E．D．’S________．

A．waste a lot ofenergy                   B．need shorter timeto make

C．shine muchbrighter                D．are warmer totouch

49．According to the passage, we know that L．E．D．’s________．

A．will replace all thelights            B．will be more and more popular

C．will be only coloredones              D．will be only usedin developing countries

50．According to the passage, we can infer that the purpose of the LightUp the World Foundation is to________．

A．develop L．E．D．lighting system for thedevelopingworld                   

B．sell bright white L．E．D．’s

C．collect money for developingcountries                                        

D．earn money by selling L．E．D．’s

试题答案

【答案】

 C

 B

 A

【解析】