（推荐）专业英语李白萍版(wust期末考)第10章要点

1、Unit 10 Lasers,Passage A What is a Laser? Passage B Introduction: Super-tool Passage C Lasers,When real lasers finally arrivedin 1960writers and moviemakers immediately leaped upon their destructive power and substituted the word “laser” for ray gun. But this image of the laser is a reflection more

2、of the need for drama in works of fiction than of the lasers potential usefulness in our society. The nice sharp pictures of laser beams in this book are taken by projecting the beams through clouds of smoke, which scatter their light enough to allow them to be seen and photographed.,Think of it sim

3、ply as a tool. One that uses light instead of mechanical energy. Intensity is a measure of power per unit area, and even a laser that emits only a few milli-watts can produce a lot of intensity in a beam thats only a millimeter in diameter.1 One of the first laser beams shot at the moonin 1962spread

4、 out only two and a half miles on the lunar surface. Not bad when you consider that it had traveled a quarter of a million miles!,Laser beams have been produced in every color of the rainbow (red is the most common laser color), as well as in many kinds of invisible light, but each laser can emit on

5、e color and one color only. A few lasers can emit several monochromatic wavelengths at oncebut not a continuous spectrum containing all the colors of visible light as a light bulb does., Lasers produce light of only one color. Or, to say it in a more technical way, the light is monochromatic. Ordina

6、ry light combines all the colors of visible light (i.e., the spectrum). Mixed together, they come out white. Laser beams have been produced in every color of the rainbow (red is the most common laser color), as well as in many kinds of invisible light, but each laser can emit one color and one color

7、 only. There are such things as tunable lasers, which can be adjusted to produce several different colors, but even they can emit only one color at a time.2 A few lasers can emit several monochromatic wavelengths at oncebut not a continuous spectrum containing all the colors of visible light as a li

8、ght bulb does. And then there are many lasers that project invisible light, such as infrared and ultraviolet light.,NOTES 1 Intensity is a measure of power per unit area, and even a laser that emits only a few milli-watts can produce a lot of intensity in a beam thats only a millimeter in diameter.强

9、度是每单位面积上能量的度量，即使一个仅产生几毫瓦能量的激光器也能产生一个直径只有1毫米的高强度光束。 后半句的主句为a lasercan produce a lot of intensity in a beam。,2 Laser beams have been produced in every color of the rainbow (red is the most common laser color), as well as in many kinds of invisible light, but each laser can emit one color and one color

10、 only. 激光束可以是彩虹中的每一种颜色(红色是最常见的激光颜色), 还可以是许多种看不见的光, 但每个激光器能且只能发出一种颜色的光。 ,Exercises 1. Fill in the blanks. (1) When real lasers finally arrivedin 1960writers and moviemakers immediately their destructive power and substituted the word “laser” for ray gun. (2) The lasers bright, red, thick beam easily

11、cut a swath the table. (3) One that uses light mechanical energy. (4) But the beam that a laser differs from the light that comes out of a flashlight in four basic ways. (5) Intensity is a measure of power per unit area, and even a laser that emits only a few milli-watts can produce intensity in a b

12、eam thats only a millimeter .,(6) The beam begins to spread out it leaves the flashlight, eventually dispersing to be useless. (7) A few lasers can emit several wavelengths at oncebut not a continuous spectrum containing all the colors of visible light as a light bulb does.,2. True/False. (1) A lase

13、r was one of the leading pieces of machinery in the James Bond techno-spy thriller Goldfinger in the early 1970s.( ) (2) This is, alas, the most popular image of the laser. A ray gun. A death ray. And indeed, some lasers do cut through metal and some can be used as weapons.( ) (3) Most laser beams c

14、an cut or burn and are at best faint pencil lines in the air, light scattered by dust.( ) (4) It cant perform a task as dramatic as igniting a thermonuclear fusion reaction or as seemingly mundane as drilling a hole in a baby-bottle nipple.( ),(5) An ordinary light bulb emits more light than a small

15、 laser like this, but that light spreads out all over the room.( ) (6) An ordinary light source, such as a light bulb, generates light waves that start at different times and head in different directions.( ) (7) There are such things as tunable lasers, which can be adjusted to produce several differ

16、ent colors, but even they can emit only one color at a time.( ),Passage B Introduction: Super-tool What Are Lasers Good For? The range of uses for the laser is striking, going far beyond the original ideas of the scientists who developed the first models(though they dont like to admit this), as well

17、 as vastly beyond the visions of the early science-fiction writers, who more often than not were simply looking for a futuristic weapon(though they too are not about to admit their lack of vision).1,The wide variety of lasers is also striking. At one end of the scale, there are lasers made from tiny

18、 semiconductor chips similar to those used in electronic circuits, no larger than grains of salt (a kind of laser that Gordon Gould, one of the pioneers of the field, says surprised him when it was introduced). At the other end, there are the building-size laser weapons that the military is testing,

19、 quite different from the hand-held ray guns of science-fiction writers.,Our purpose in this book is not only to explain lasers but to tell you about all the ways in which theyre now usedand will be used in the near futureand about how lasers will therefore affect our lives. The tasks that lasers pe

20、rform range from the mundane to the esoteric, but they usually have a common element: they are difficult or impossible with any other tool.2 Lasers are relatively expensive tools and are usually brought in to do a job only because they can deliver the required type and amount of energy to the desire

21、d spot. Charles H. Townes, one of the inventors of the laser and a Nobel prize-winner, told us recently that he believes the laser “is going to touch on a very great number of areas. The laser will do almost anything. But it costs. That is the only limitation.”,The $50,000 Scalper and Television Fib

22、ers A typical surgical laser, for example, costs from $30,000 to $50,000 and up, or about a thousand times more than a good conventional scalpel. And to be honest, for many operations a scalpel may be better than a laser. But if you have a detached retina, a condition that could lead to blindness, y

23、ou may be happy that these expensive scalpels exist. A laser can do what a knife cant: weld the retina back to the eyeball. No incision is required for this delicate surgery, which can be performed right in the doctors office. The laser beam shines through the lens of the patients eye and is focused

24、 on the retina, producing a small lesion,that helps hold it to the eyeball. Exotic as this sounds, a similar laser treatment has become a standard way of curing blindness caused by diabetes. (Charles Townes finds this application of the laser amazing. He admitted to us recently that the adaptation o

25、f the laser for medical uses took him by surprise, especially the detached retina procedure.),Laser medicine probably hasnt touched you personally(youd know if it had), but laser communication has undoubtedly served you already. If you watched the 1980 Winter Olympics from Lake Placid, New York, or

26、any recent football game from Tampa Bay (Florida) Stadium on television, you saw signals that were transmitted part of the way to your home by laser. Lasers carry telephone signals in dozens of places around the country. In both cases, light from the lasers is carried through hair-thin fibers of gla

27、ssfiber opticsa technology that could ultimately bring a multitude of new communication services into your home.,Death Rays, Drills, Nuclear Fusion Lasers are already commonplace items among our military, but probably not in the way you think. Their main function in the business of war is that of ra

28、nge finder and target designator, not ray gun. Lasers measure the distances to targets or pinpoint them with a “bulls-eye,” helping either guns or missiles to home in on the enemy. And yes, in an offshoot of H. G. Wellss idea, the U.S. military is also spending about $300 million a year trying to bu

29、ild lasers able to destroy targets ranging from helicopters to ballistic missiles and satellites. The Soviet Union has a comparable program and is believed to have already used a laser to temporarily blind the sensitive electronic “eyes” of a U.S. spy satellite.,In factories around the world, lasers

30、 are now used routinely to drill holes in diamonds, label automotive parts, and weld battery cases for heart pacemakers. Laser quality-control “inspectors” sit ever-vigilant on assembly lines, making sure that the sizes of parts do not deviate from an acceptable range. One of the hopes for ending ou

31、r energy problems is thermounuclear fusion, the process by which our sun generates its energy. One way of creating fusion here on earth is to heat and compress pellets containing hydrogen to the temperatures and pressures needed to fuse the nuclei of the hydrogen atoms together, creating tiny hydrog

32、en bombs and thus generating incredible power.3 What can compress these pellets? Lasers, of course.,Three-dimensional Images and Super Readers Lasers are what make holograms possiblethose three-dimensional images that seem to float before you, suspended in space. But holography has many seemingly mu

33、ndane applications as well, from testing the quality of aircraft tires to measuring heat flow to aiding in the design of such things as hair dryers. Lasers have made new art and new entertainment forms possible, even beyond holography. Laser light shows, the best known of which is Laserium, have bee

34、n seen by millions of people around the world. A laser is also at the heart of one type of videodisk player, that new device that plays back movies and television programs prerecorded on phonograph like disks.,Lasers can read. Those cryptic bar codes on food packages in supermarkets are read by scan

35、ning them with a laser beam. The pattern of reflected light is decoded to tell a computer in the back of the store what the label says. This not only tabulates the price on the cash register but automatically registers in the computers inventory memory. Lasers also read special typewriter faces, so

36、that manuscripts can be typeset automatically, without human aid. And laser can write. Its simple for a computer to control a laser, making it write on film, special paper, or the drum of a copying machine, for later transfer to paper. Laser expose printing plates for newspapers and print statements

37、 for insurance companies and mutual funds.,NOTES 1 The range of uses for the laser is striking, going far beyond the original ideas of the scientists who developed the first models (though they dont like to admit this), as well as vastly beyond the visions of the early science-fiction writers, who m

38、ore often than not were simply looking for a futuristic weapon (though they too are not about to admit their lack of vision).激光的用途极其广泛，令人瞩目，远远超出了设计第一代模型的科学家们的想像(尽管他们不愿承认)，也极大地超出了早期科幻小说家的想像，这些小说家只是单纯地寻找一种未来武器(尽管他们也不愿承认自己缺乏想像力)。,2 The tasks that lasers perform range from the mundane to the esoteric, b

39、ut they usually have a common element: they are difficult impossible with any other tool.激光器能完成从平凡到神秘的多种任务，但这些任务通常都有一个共同点：它们很难或不可能由其他工具来完成。 句中的两个they均指the tasks。,3 One way of creating fusion here on earth is to heat and compress pellets containing hydrogen to the temperatures and pressures needed to

40、 fuse the nuclei of the hydrogen atoms together, creating tiny hydrogen bombs and thus generating incredible power.在地球上实现熔合的途径是对含有氢气的气团加温加压，以达到使氢原子熔合的温度和压力，产生小型氢弹，因而出现难以想像的巨大能量。,Exercises 1. Fill in the blanks. (1) At one end of the scale, there are lasers tiny semiconductor chips similar to those u

41、sed in electronic circuits, no larger than grains of salt. (2) Charles H. Townes, one of the inventors of the laser and a Nobel prize-winner, told us recently that he believes the laser “is going to touch on areas”. (3) The laser beam shines through the lens of the patients eye and is the retina, pr

42、oducing a small lesion that helps hold it to the eyeball.,(4) In both cases, light from the lasers is hair-thin fibers of glassfiber opticsa technology that could ultimately bring a multitude of new communication services your home. (5) The pattern of reflected light is decoded to tell a computer th

43、e store what the label says.,2. True/False. (1) Lasers carry telephone signals in dozens of places around the country. ( ) (2) Lasers measure the distances to targets or pinpoint them with a “bulls-eye,” helping either guns or missiles to home in on the enemy. ( ) (3)In factories around the world, l

44、asers are now used routinely to drill holes in diamonds, label automotive parts, and weld battery cases for heart pacemakers.( ) (4)Lasers are what make holograms impossiblethose three-dimensional images that seem to float before you, suspended in space.( ),(5)Laser expose printing plates for newspa

45、pers and print statements for insurance companies and mutual funds.( ) (6)Lasers cant cause and control chemical reactions and someday might even propel rockets and aircraft. Well cover all these things in the following pages.( ),Passage C Lasers To understand what a laser (Light Amplification by St

46、imulated Emission of Radiation) is, one has to understand how light generated. Light comes from the electrons which surround the nucleus of every normal atom. When the atom, let us say, of sodium, is in its unexcited state the electrons that surround the sodium nucleus are in their normal energy lev

47、els. If this sodium atom absorbs some energy from outside, one or more of the electrons jumps from a low energy level to a higher energy level. The atom then remains in this excited state until it is able to release the energy it has temporarily stored. When this release occurs the electron in the h

48、igh energy level falls back to the low energy level. But as it does so it emits the extra energy as a pulse we may see as light.,The laser beam is made by exciting the atoms of a suitable material until most of the atoms have electrons orbiting in a higher energy level than usual. The excitation is then stopped and all the excited electrons fall back together to their normal orbits, each one emitting a pulse of light of the same energy, which generates an intense beam of light for a very short time. Every pulse in this beam is i