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共用题干
Learn about Light
1 .Ancient civilizations were amazed by the existence of light for thousands of years. The Greek philosophers believed that light was made up of countless,tiny particles that enter the human eye and create what we call vision. However,Empedocles and a Dutch scientist named Christian Huygens believed that light was like a wave. According to them,light spread out and travelled like a straight line. This theory was accepted during the 19th century.
2 .In 1905,Albert Einstein published a research paper in which he explained what is re-ferred to as the photoelectric effect. This theory explains that particles make up light.The particles Einstein was referring to are weightless bundles（束）of electromagnetic（电磁）energy called photons（光子）.Today,scientists agree that light has a dual（二重）nature一it is part particle and part wave. It is a form of energy that allows us to see things around us.
3 .Things that give off light are known as sources of light. During the day,the primary source of light is the sun. Other sources of light include stars,flames,flashlights,street lamps and glowing gases in glass tube.
4 .When we draw the way light travels we always use straight lines. This is because nor-mally light rays travel in a straight line. However,there are some instances that can change the path and even the nature of light. They are reflection,absorption,interference（干扰）, etc.
5 .Physicists have attempted to measure the speed of light since the early times. In 1849, Hippolyte Fizeau conducted an experiment by directing a beam of light to a mirror located kilometers away and placed a rotating cogwheel（旋转齿轮）between the beam and the mirror. From the rate of rotation of the wheel,number of wheel's teeth and distance of the mirror,he was able to calculate that the speed of light is 313 million meters per second. In a vacuum（真空）,however,the speed of light is 299,792,458 meters per second. This is about a million times faster than the speed of an airplane.

Some instances such as reflection and absorption can change______.
A: sources of light
B: the speed of light
C: the path of light
D: a straight line
E: a beam of light
F: a form of energy

参考答案

参考解析
解析：该概括大意与完成句子所选的阅读材料为记述文，段落主题相对于论述文而言较松散，因此记述文中的段落大意往往需要考生根据自己的理解而归纳概括出来。解答概括大意题的技巧往往派不上用场。第二段主要讲述现代科学家认同了爱因斯坦的光电效应理论。因此可以判断A选项“当今人们如何解释光的性质”正确。
第三段第一句“Things that give off light are known as sources of light.”就点明主旨，发光的物体是光源。所以B选项“什么是光源？”正确。
第四段主要讲述光传播的问题，所以D选项“光是如何传播的”正确。
第五段的关键字是speed of light，光速。所以C选项“物理学家如何测量光的速度”正确。
题干意为“人们可以看见物体是因为光……。“从第二段最后一句可知，人们看见物体是因为光是一种能量。所以F项a form of energy正确的。
题干意为“星星、火焰、手电筒都是……的例子。”第三段“Other sources of light include stars , flames , flashlights...”说明，这些都是光源的例子。所以A选项sourcesof light是正确的。
题干意为“某些情况下，如反射和吸收可以改变……。”第四段中“there are some instances that can change the path and even the nature of light.They are reflection,ab-sorption , interference , etc.”这说明有一些情况可以改变光的路径。所以C选项the path of light是正确的。
题干意为“Hippolyte Fizeau做了一个刚试……的实验。”文中最后一段 “Hippolyte Fizeau conducted an experiment by directing a beam of light to a mirror...he was able to calculate that the speed of light...”可知Hippolyte Fizeau通过实验计算出了光速。所以B选项是正确的。
更多 “共用题干 Learn about Light1 .Ancient civilizations were amazed by the existence of light for thousands of years. The Greek philosophers believed that light was made up of countless,tiny particles that enter the human eye and create what we call vision. However,Empedocles and a Dutch scientist named Christian Huygens believed that light was like a wave. According to them,light spread out and travelled like a straight line. This theory was accepted during the 19th century.2 .In 1905,Albert Einstein published a research paper in which he explained what is re-ferred to as the photoelectric effect. This theory explains that particles make up light.The particles Einstein was referring to are weightless bundles（束）of electromagnetic（电磁）energy called photons（光子）.Today,scientists agree that light has a dual（二重）nature一it is part particle and part wave. It is a form of energy that allows us to see things around us.3 .Things that give off light are known as sources of light. During the day,the primary source of light is the sun. Other sources of light include stars,flames,flashlights,street lamps and glowing gases in glass tube.4 .When we draw the way light travels we always use straight lines. This is because nor-mally light rays travel in a straight line. However,there are some instances that can change the path and even the nature of light. They are reflection,absorption,interference（干扰）, etc.5 .Physicists have attempted to measure the speed of light since the early times. In 1849, Hippolyte Fizeau conducted an experiment by directing a beam of light to a mirror located kilometers away and placed a rotating cogwheel（旋转齿轮）between the beam and the mirror. From the rate of rotation of the wheel,number of wheel's teeth and distance of the mirror,he was able to calculate that the speed of light is 313 million meters per second. In a vacuum（真空）,however,the speed of light is 299,792,458 meters per second. This is about a million times faster than the speed of an airplane.Some instances such as reflection and absorption can change______.A: sources of lightB: the speed of lightC: the path of lightD: a straight lineE: a beam of lightF: a form of energy” 相关考题
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考题 共用题干 第三篇Small but WiseOn December 14,NASA blasted a small but mighty telescope into space.The telescope is called WISE and is about as wide around as a trashcan.Don't let its small size fool you:WISE has a powerful digital camera,and it will be taking pictures of some of the wildest objects in the known universe,including asteroids,faint stars,blazing galaxies and giant clouds of dust where planets and stars are born."I'm very excited because we're going to be seeing parts of the universe that we haven't seen be- fore,"said Ned Wright,a scientist who directs the WISE project.Since arriving in space,the WISE telescope has been circling the Earth,held by gravity in a polar orbit (this means it crosses close to the north and south poles with each lap).Its camera is pointed outward,awayfrom the Earth,and WISE will snap a picture of a different part of the sky every 11 minutes.After six months it will have taken pictures across the entire sky.The pictures taken by WISE won't be like everyday digital photographs,however. WISE stands for "Wide-field Infrared Survey Explorer".As its name suggests,the WISE camera takes pictures of features that give off infrared radiation.Radiation is energy that travels as a wave.Visible light,including the familiar spectrum of light that be- comes visible in a rainbow,is an example of radiation.When an ordinary digital camera takes a picture of a tree,for example,it receives the waves of visible light that are reflected off the tree.When these waves enter the camera through the lens,they're processed by the camera,which then puts the image together.Waves of infrared radiation are longer than waves of visible light,so ordinary digital cameras don't see them,and neither do the eyes of human beings.Although invisible to the eye,longer infrared radiation can be detected as warmth by the skin.That's a key idea to why WISE will be able to see things other telescopes can't. Not everything in the universe shows up in visible light.Asteroids,for example, are giant rocks that float through space一but they absorb most of the light that reaches them.They don't reflect light,so they're difficult to see.But they do give off infrared radiation,so an infrared telescope like WISE will be able to produce images of them.During its mission WISE will take pictures of hundreds of thousands of asteroids.Brown dwarfs are another kind of deep-space objects that will show up in WISE's pictures.These ob- jects are "failed" stars一which means they are not massive enough to jump-start the same kind of reactions that power stars such as the sun.Instead,brown dwarfs simply shrink and cool down.They're so dim that they're almost impossible to see with visible light,but in the infrared spectrum they glow.What is so special about WISE?A:It is as small as a trashcan.B:It is small in size but carries a large camera.C:Its digital camera can help astronomers to see the unknown space.D:Never before has a telescope carried a digital camera in space.
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考题 共用题干 Learn About Light1 Ancient civilizations were amazed by the existence of light for thousands of years?The Greek philoso- phrrs believed that light was made up of countless,tiny particles that enter the human eye and create what we call vision.However,Empedocles and a Dutch scientist named Christian Huygens believed that light wag like a wave.According to them,light spread out and travelled like a straight line.This theory was acceptedduring the 19th century.2 In 1905,Albert Einstein published a research paper in which he explained what is referred to as the photoelectric effect.This theory explains that particles make up light.The particles Einstein was referring to are weightless bundles（束）of electromagnetic（电磁）energy called photons（光子）.Today,scientists agree that light has a dual（二重）nature一it is part particle and part wave. It is a form of energy that allows us tosee things around us.3 Things that give off light are known as sources of light.During the day,the primary source of light is the sun.Other sources of light include stars,flames,flashllights,street lamps and glowing gases in glass tube.4 When we draw the way light travels we always use straight lines.This is because normally light rays travel in a straight line.However,there are some instances that can change the path and even the nature of light. They are reflection,absorption,interference（干扰）,etc.5 Physicists have attempted to measure the speed of light since the early times.In 1849,Hippolyte Fizeau conducted an experiment by directing a beam of light to a mirror located kilometers away and placed a rotating cogwheel（旋转齿轮）between the beam and the mirror. From the rate of rotation of the wheel, number of wheel'S teeth and distance of the mirror,he was able to calculate that the speed of light is 313 million meters per second.In a vacuum（真空）,however,the speed of light is 299,792,458 meters per second.This is about a million times faster than the speed of an airplane.Paragraph 4________A:How is the Nature of Light Explained Today?B:What are Sources of Light?C:How did Physicists Measure the Speed of Light?D:How does Light Travel?E:How did People Think of Light Years Ago?F: What Causes a Shadow?
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考题 共用题干 第三篇Shouldn't We Know Who Invented the Windshield WiperWe know the famous ones一the Thomas Edison and the Alexander Graham Bells一but what about the less famous inventors?What about the people who invented the traffic light and the windshield wiper（雨刷器）?Shouldn' t we know who they are?Joan Mclean thinks so.In fact,Mclean,a professor of physics at Mountain University in Range,feels so strongly about this matter that she's developed a course on the topic.In addition to learning" who"invented"what",however,Mclean also likes her students to learn the answers to the"why"and"how" questions.According to Mclean,"when students learn the answers to these questions,they are better prepared to recognize opportunities for inventing and more motivated to give inventing a try".Her students agree.One young man with a patent for an unbreakable umbrella is walking proof of McLean's statement."If I had not heard of the story of the windshield wiper's invention,"said Tommy Lee,a senior physics major,"I never would have dreamed of turning my bad experience during a rainstorm into something so constructive."Lee is currently negotiating to sell his patent to an umbrella producer.So,just what is the story behind the windshield wiper? Well,Mary Anderson came up with the idea in 1902 after a visit to New York City. The day was cold and stormy,but Anderson still wanted to see the sights,so she jumped aboard a streetcar. Noticing that the driver was struggling to see through the snow covering the windshield,she found herself wondering why there couldn't be a built-in device for cleaning the window. Still wondering about this when she returned home to Birmingham,Alabama,Anderson started drafting out solutions. One of her ideas,a lever（操作杆）on the inside of a vehicle that would control an arm on the outside,became the first windshield wiper.Today we benefit from countless inventions and innovations,It's hard to imagine driving without Garrett A.Morgan's traffic light. It'5equally impossible to picture a world without Katherine J. Blodgett's innovation that makes glass invisible.Can you picture life without clear windows and eyeglasses?What can we learn from this article?A:Teachers should help students to sell their inventions to producers.B:How to design a built-in device for cleaning the window.C:We should know less famous inventors.D:We should develop invention courses in universities.
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考题 共用题干 第三篇Weaving with LightIn the Sierra Madre mountain range of west central Mexico,the native Huichol people live much the way their ancestors did一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一at home or on the road,they can only work during daylight hours?When it gets dark,they must stop whatever they'redoing.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 atnight一 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.At the core of Portable Lights 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 mnean- descent lights,however,is heat一and invisible.With all that wasted energy,bulbs burn out quickly. Theyare 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 a LED,the crystal structure produces light. Un- like incandescent bulbs,they can produce light of various colors.Within a LED,the type of molecules and their particular arrangement determine what color is produced.The central part of the Portable Lights technology is_________.A:glass bulbsB:digital clocksC:incandescent lightsD:HB LEDs
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考题 共用题干 第三篇Shouldn't We Know Who Invented the Windshield WiperWe know the famous ones一the Thomas Edison and the Alexander Graham Bells一but what about the less famous inventors?What about the people who invented the traffic light and the windshield wiper（雨刷器）?Shouldn' t we know who they are?Joan Mclean thinks so.In fact,Mclean,a professor of physics at Mountain University in Range,feels so strongly about this matter that she's developed a course on the topic.In addition to learning" who"invented"what",however,Mclean also likes her students to learn the answers to the"why"and"how" questions.According to Mclean,"when students learn the answers to these questions,they are better prepared to recognize opportunities for inventing and more motivated to give inventing a try".Her students agree.One young man with a patent for an unbreakable umbrella is walking proof of McLean's statement."If I had not heard of the story of the windshield wiper's invention,"said Tommy Lee,a senior physics major,"I never would have dreamed of turning my bad experience during a rainstorm into something so constructive."Lee is currently negotiating to sell his patent to an umbrella producer.So,just what is the story behind the windshield wiper? Well,Mary Anderson came up with the idea in 1902 after a visit to New York City. The day was cold and stormy,but Anderson still wanted to see the sights,so she jumped aboard a streetcar. Noticing that the driver was struggling to see through the snow covering the windshield,she found herself wondering why there couldn't be a built-in device for cleaning the window. Still wondering about this when she returned home to Birmingham,Alabama,Anderson started drafting out solutions. One of her ideas,a lever（操作杆）on the inside of a vehicle that would control an arm on the outside,became the first windshield wiper.Today we benefit from countless inventions and innovations,It's hard to imagine driving without Garrett A.Morgan's traffic light. It'5equally impossible to picture a world without Katherine J. Blodgett's innovation that makes glass invisible.Can you picture life without clear windows and eyeglasses?By mentioning"traffic light"and"windshield wiper",the author indicates that countless inventions are______.A:beneficial,because their inventors are famousB:beneficial,though their inventors are less famousC:not useful,because their inventors are less famousD:not useful,though their inventors are famous
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考题 共用题干 Cell PhonesI Believe it or not,cell phones have been around for over a quarter of a century.The first commercial cell phone systemfl was developed by the Japancoc in I 979.But cell phones have changed a lotsince that time.The early cell phones were big and heavy but they have developed into small and light palm-sized mod- els.There have been huge (lcveloprnents in their functions,too;we have had call forwarding,text messaging, answering services and hands-free use for years,but now there are countless new facilities,su,ch as instant ac- cess to the Internet and receiving and sending photos.2 Cell phones have become very common in our lives;recent statistics suggest as many as one in three people cii the planet now have a cell phone,and most of them say they couldn't live without one.Cell phones are used in every area of our lives and have become a necessary tool,used for essential arrangements,socialcontact and business.They have made it easier to call for help on the highway.They have made it possible tokeep in touch with people"on the move”一when people are traveling.3 Cell phones have made communication easier and have reduced the need for family arguments.Wecan use cell phones to let our family know we'11 be late or if there’。a sudden change of tian or an emergen- cy.Cell phones have eased the worries of millions of parents when their teenagers are out late,they can nowcontact their children at any time.4 This does not mean that cell phones are all good news.They have brought with them a number of new headaches for their owners;it costs a lot to replace stolen phones,something that is becoming a frequent occurrence,and have you ever seen such huge phone bills? More serious,however,is the potential healthproblem they bring:there are fears that radiation from the phones may cause brain tumor（肿瘤）.This may be a time bomb waiting to happen to younger people who have grown up with cell phones that they simply can'tlive without!We can use cell phones to communicate with others when we encounter__________. A:a necessityB:an emergencyC:a number of new hcadachesD:family argumentsF:big and light palm-sized models F:countless new facilities
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考题 共用题干 第三篇Ways to Create Colors in a PhotographThere are two ways to create colors in a photograph.One method called additive,starts with three basic colors and adds them together to produce some other color. The second method,called subtractive,starts with white light(a mixture of all colors in the spectrum)and,by taking away some or all other colors,leaves the one desired.In the additive method,separate colored lights combine to produce various other colors.The three additive primary colors are green,red and blue(each providing about one-third of the wavelengths in the total spectrum).Mixed in varying proportions,they can produce all colors.Green and red light mix to produce yellow,red and blue light mix to produce magenta(a purplish pink);green and blue mix to produce cyan(a bluish green).When equal parts of all three of these primary-colored beams of light overlap（重叠）,the mixture appears white to the eye.In the subtractive process colors are produced when dye（染料）absorbs some wavelengths and so passes on only part of the spectrum.The subtractive primaries are cyan,magenta and yellow; these primaries or dyes absorb red,green and blue wavelengths respectively,thus subtracting them from white light. These dye colors are the complementary colors to the three additive primaries of red,green and blue.Properly combined,the subtractive primaries can absorb all colors of light, producing black.But,mixed in varying proportions,they too can produce any color in the spectrum.Whether a particular color is obtained by adding colored lights together or by subtracting some light from the total spectrum,the result looks the same to the eye.The additive process was employed for early color photography. But the subtractive method,while requiring complex chemical techniques,has turned out to be more practical and is the basis of all modern color films.What color filter would absorb red wavelengths?A:Red. B:Magenta.C:Cyan. D:Yellow.
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考题 共用题干 第三篇Weaving with LightIn the Sierra Madre mountain range of west central Mexico,the native Huichol people live much the way their ancestors did一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一at home or on the road,they can only work during daylight hours?When it gets dark,they must stop whatever they'redoing.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 atnight一 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.At the core of Portable Lights 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 mnean- descent lights,however,is heat一and invisible.With all that wasted energy,bulbs burn out quickly. Theyare 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 a LED,the crystal structure produces light. Un- like incandescent bulbs,they can produce light of various colors.Within a LED,the type of molecules and their particular arrangement determine what color is produced.To make a living,the Huichol create artwork and_________.A:sell it to tourists in their villagesB:sell it in cities far away from their villagesC:display it in their village museumsD:keep it in their homes to attract tourists
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考题 共用题干 Learn About Light1 Ancient civilizations were amazed by the existence of light for thousands of years?The Greek philoso- phrrs believed that light was made up of countless,tiny particles that enter the human eye and create what we call vision.However,Empedocles and a Dutch scientist named Christian Huygens believed that light wag like a wave.According to them,light spread out and travelled like a straight line.This theory was acceptedduring the 19th century.2 In 1905,Albert Einstein published a research paper in which he explained what is referred to as the photoelectric effect.This theory explains that particles make up light.The particles Einstein was referring to are weightless bundles（束）of electromagnetic（电磁）energy called photons（光子）.Today,scientists agree that light has a dual（二重）nature一it is part particle and part wave. It is a form of energy that allows us tosee things around us.3 Things that give off light are known as sources of light.During the day,the primary source of light is the sun.Other sources of light include stars,flames,flashllights,street lamps and glowing gases in glass tube.4 When we draw the way light travels we always use straight lines.This is because normally light rays travel in a straight line.However,there are some instances that can change the path and even the nature of light. They are reflection,absorption,interference（干扰）,etc.5 Physicists have attempted to measure the speed of light since the early times.In 1849,Hippolyte Fizeau conducted an experiment by directing a beam of light to a mirror located kilometers away and placed a rotating cogwheel（旋转齿轮）between the beam and the mirror. From the rate of rotation of the wheel, number of wheel'S teeth and distance of the mirror,he was able to calculate that the speed of light is 313 million meters per second.In a vacuum（真空）,however,the speed of light is 299,792,458 meters per second.This is about a million times faster than the speed of an airplane.Hippolyte Fizeau conducted an experiment to measure_________.A:sources of lightB:the speed of light C:the path of lightD:a straight lineE:a beam of lightF:a form of energy
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考题 共用题干 Learn About Light1 Ancient civilizations were amazed by the existence of light for thousands of years?The Greek philoso- phrrs believed that light was made up of countless,tiny particles that enter the human eye and create what we call vision.However,Empedocles and a Dutch scientist named Christian Huygens believed that light wag like a wave.According to them,light spread out and travelled like a straight line.This theory was acceptedduring the 19th century.2 In 1905,Albert Einstein published a research paper in which he explained what is referred to as the photoelectric effect.This theory explains that particles make up light.The particles Einstein was referring to are weightless bundles（束）of electromagnetic（电磁）energy called photons（光子）.Today,scientists agree that light has a dual（二重）nature一it is part particle and part wave. It is a form of energy that allows us tosee things around us.3 Things that give off light are known as sources of light.During the day,the primary source of light is the sun.Other sources of light include stars,flames,flashllights,street lamps and glowing gases in glass tube.4 When we draw the way light travels we always use straight lines.This is because normally light rays travel in a straight line.However,there are some instances that can change the path and even the nature of light. They are reflection,absorption,interference（干扰）,etc.5 Physicists have attempted to measure the speed of light since the early times.In 1849,Hippolyte Fizeau conducted an experiment by directing a beam of light to a mirror located kilometers away and placed a rotating cogwheel（旋转齿轮）between the beam and the mirror. From the rate of rotation of the wheel, number of wheel'S teeth and distance of the mirror,he was able to calculate that the speed of light is 313 million meters per second.In a vacuum（真空）,however,the speed of light is 299,792,458 meters per second.This is about a million times faster than the speed of an airplane.Objects are visible to the human eye as light is_______. A:sources of lightB:the speed of light C:the path of lightD:a straight lineE:a beam of lightF:a form of energy
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考题 共用题干 第三篇Weaving with LightIn the Sierra Madre mountain range of west central Mexico,the native Huichol people live much the way their ancestors did一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一at home or on the road,they can only work during daylight hours?When it gets dark,they must stop whatever they'redoing.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 atnight一 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.At the core of Portable Lights 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 mnean- descent lights,however,is heat一and invisible.With all that wasted energy,bulbs burn out quickly. Theyare 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 a LED,the crystal structure produces light. Un- like incandescent bulbs,they can produce light of various colors.Within a LED,the type of molecules and their particular arrangement determine what color is produced.LEDs are different from light bulbs in that__________.A:LEDg are made up of tiny pieces of rockB:LEDs can send out light of different colorsC:LEDs belong to incandescent lightsD:LEDs look like crystals
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考题 共用题干 第三篇Weaving with LightIn the Sierra Madre mountain range of west central Mexico,the native Huichol people live much the way their ancestors did一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一at home or on the road,they can only work during daylight hours?When it gets dark,they must stop whatever they'redoing.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 atnight一 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.At the core of Portable Lights 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 mnean- descent lights,however,is heat一and invisible.With all that wasted energy,bulbs burn out quickly. Theyare 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 a LED,the crystal structure produces light. Un- like incandescent bulbs,they can produce light of various colors.Within a LED,the type of molecules and their particular arrangement determine what color is produced.The Huichol don't use electricity because ________.A:it is too difficult for them to change their lifestyleB:they know nothing about itC:it costs too much to string power linesD:they don't need it
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考题 If you are writing or studying,it makes very much difference where the light comes from.People who use books and pens every day have to be especially careful about the way the light shines on their work. Every house gets its light either from daylight through the windows--which is the best to use--or from lamps or electricity;but whichever kind of light it is,the way it shines toward our book or work is a matter of great importance to the eyes. Take a book,sit with your back toward the window,and try to read.Your shadow（影子）falls all over the page and makes it almost as bad for your eyes as if you were in a dark room. Now turnaround and face the window.The page is in the shadow again,while the bright light is in your eyes. Try sitting with your right side toward the window.This is very well for reading,but if you were writing,the shadow of your hand would fall across the page and bother（打搅）you a little. There is just one other way:sit with your left side to the window.Now everything is perfect for reading and for writing,too. Whatever kind of light is in the room,the rule about the right to sit is always the same. Which of the following is true?A.How the light shines on our work is of much importance. B.The way the light shines on your work makes no difference. C.We needn't care about where the light comes from. D.People can write or study under a light that comes from any direction.
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考题 What physical characteristic does a retinal scan biometric device measure?视网膜扫描设备检测哪些人体物理特性？（）A、The pattern of light receptors at the back of the eye眼底光受体组织的图案B、The pattern of blood vessels at the back of the eye眼底血管的图案C、The amount of light reaching the retina视网膜受光量
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考题 填空题We were surprised at the (achieve) ____ the young man had made in the last three years.
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考题 单选题What kind of conditions would you observe as the eye of a storm passes over your ship’s position（）.A Huge waves approaching from all directions，clearing skies，light winds，and an extremely low barometerB Flat calm seas，heavy rain，light winds，and an extremely low barometerC Flat calm seas，heavy rain，light winds，and high pressureD Huge waves approaching from all directions，clearing skies，light winds，and high pressure
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考题 单选题What Call We learn about the Greyhound tickets?A They are not available for traveling outside the U. S.B Travelers should buy their tickets in person.C Babies Call not travel free with their parents.D They have the exact travel date on them.
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