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  3. 共用题干 Electromagnetic Energy1 White light seems to be a combination of all co...

共用题干 Electromagnetic Energy1 White light seems to be a combination of all co...

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问题 共用题干
Electromagnetic Energy
1 White light seems to be a combination of all colors.The energy that comes from a source of light is not limited to the kind of energy you can see.Heat is given off by a flame or an electric light.On a cloudy day it is possible to get a sunburn even though you feel cool.Visible light and the kinds of energy that produce warmth and sunburn are examples of electromagnetic energy.
2 The sun is 93 million miles from the earth.Yet we can use energy from the sun because electromagnetic energy travels through space.
3 Many other kinds of energy are also types of electromagnetic energy.Radio,television,and radar signals travel from transmitters to receivers as low-energy electromagnetic waves.Infrared（红外线的）radiation is an electromagnetic wave.When it is absorbed by matter,heat is produced.Waves of infrared and visible light have more energy than waves of radio,television,or radar.Ultraviolet rays（紫外线）and X-rays are electromagnetic waves with even greater amounts of energy.Infrared radiation is used in cooking food and heating buildings. Sunlight and electric lights are part of our requirements for normal living.Ultraviolet radiation is useful in killing certain disease organisms.X-rays and gamma rays have so much energy that they travel through solid objects. They can be used to detect and treat cancer.X-rays are used in industry to find hidden cracks in metal,and in medicine to reveal broken bones.
4 Usually we use electricity to generate electromagnetic energy.The source of most of our energy is the sun.Heat from the sun causes water to evaporate.When the water falls to the earth as rain,some of it is trapped behind dams and then used to operate electric generators.Other generators are powered by coal,but the energy stored in coal came from the sun,too.
5 Until recently,the source of the tremendous amount of energy given off by the sun was a puzzle.If the sun depended on chemical reactions,it would have used up all its energy long ago.Experiments with electromagnetic radiation led to the theory that mass can be converted into energy.About forty years after the theory was proposed , nuclear energy was harnessed（利用）by man.Chemical energy comes from electron （电子）rearrangement.Nuclear energy comes from a change in the nucleus of an atom.Compared with chemical reactions,nuclear reactions release millions of times more energy per pound of fuel.We now believe that the sun's energy comes from the nuclear reactions in which hydrogen is changed into helium（氦）.
6 Nuclear energy is beginning to compete with coal as an economical source of'power to generate electricity.It is also being used to operate engines in large ships.Scientists continue to seek new and better methods of obtaining and using energy.
选项 Paragraph 5______
A:Nuclear Reactions as the Lasting Source of the Sun's Energy
B:The Most Important Source of Energy
C:Types of Electromagnetic Energy
D:The Machines Used for Energy Generation
E:Seeking New Sources of Energy
F:The Use of Ultravio1et Radiation in Medicine
答案A
解析通读文章可知，第三段第一句是段落主题句，紧接着围绕第一句进行了具体阐述，根据第一句中出现的“types of electromagnetic energy”可知，第三段主要讲述几种不同种类的电磁能，应选择C项。
根据第四段第一、二句可知，我们通常用电来生成电磁能，使用的很多能源都来自太阳。紧接着又表明，水能源于来自太阳的热能，煤储存的能量也是来自太阳。因此不难得出，第四段讲的是能量最重要的来源，即太阳。
第五段开头提到太阳能的来源仍是个谜，随后对此进行了分析，最后得出太阳能来自核反应释放的能量。由此可知，第五段主要讲的是，氢原子转变为氦原子的核反应释放的能量是太阳能的来源。几个选项中只有A项提到核反应是太阳能的持久来源，因此选择A项。
通读文章可知，第六段的最后一句是主题句。这句话的大意是：科学家正继续在寻找更好的新方法来获取并使用能源。几个选项中只有E项与之契合，因此选择E项。
根据第一段第四句可知，你即便在感到凉爽的阴天，也有可能被阳光灼伤，因此选择B项。
根据第三段第三、四句可知，红外线是电磁波，当它被物质吸收时，会产生能量。
根据第三段倒数第二、三句可知，X射线和伽马射线之所以能用来探测和治疗癌症，是因为具有很多能量的x射线和伽马射线能穿透固体。
根据第五段第五句可知，化学能是在电子重组时产生的。
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