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1、智 课 网 托 福 备 考 资 料托福听力TPO5原文 Lecture 3-智课教育旗下智课教育下面就让小编来为大家介绍一下托福听力TPO5原文中Lecture 3的 文本内容吧，大家要好好把握，这些都是非常有价值的材料，同时，大 家也可以登录智课教育论坛进行TPO练习辅导，希望能够给准备托福听 力的同学带来帮助。 TPO 5 Lecture 3 Chemistry Narrator Listen to part of a lecture in a chemistry class. Professor Okay. I know you all have a lot of questions a
2、bout this lab assignment thats coming out so . Im gonna take a little time this morning to discuss it. So, you know the assignment has to do with Spectroscopy, right? And your reading should help you get a good idea of what thats all about. But, lets talk about Spectroscopy a little now just to cove
3、r the basics.What is Spectroscopy? Well, the simplest definition I can give you is that Spectroscopy is the study of the interaction between matter and light. Now, visible light consists of different colors or wavelengths, which together make up whats called spectrum, a band of colors, like you see
4、in a rainbow. And all substances, all forms of matter, can be distinguished according to what wavelength of light they absorb and which ones they reflect. Its like, um, well, every element has, what we call, its own spectral signature. If we can read that signature, we can identify the element. And
5、thats exactly what spectroscopy does. Now, Laser Spectroscopy, which is the focus of your assignment, works by measuring very precisely what parts of the spectrum are absorbed by different substances. And it has applications in a lot of different disciplines. And your assignment will be to choose a
6、discipline that interests you, and devise anexperiment. For example, Im gonna talk about art. Im interested in the art and to me its interesting how spectroscopy is used to analyze art. Lets say a museum curator comes to you with a problem. Shes come across this painting that appears to be an origin
7、al - lets say, a Rembrandt. And she wants to acquire it for her museum. But shes got a problem： shes not absolutely certain its an original. So, what do you do? How do you determine whether the paintings authentic? Okay. Think about the scientific process. Youve got the question： Is the painting a R
8、embrandt? So first, youll need to make a list of characteristics the painting would have to have to be a Rembrandt. Then you have to discover whether the painting in question has those characteristics.So first of all, youll need to know the techniques Rembrandt used when he applied paint to canvas -
9、 his brushstrokes, how thickly he applied his paint. So youd need to work with an art historian who has expert knowledge of Rembrandts style. Youd have to know when he created his paintings, um. what pigments he used, in other words, what ingredients he used to make different colors of paint, cause
10、the ingredients used in paints and binding agents plus burnishes, finishes, what have you, have changed over time. Since youre trying to verify if its a Rembrandt, the ingredients in the pigment would need to have been used during Rembrandts lifetime - in the 17th century. And thats where chemistry
11、comes in. Youve got to find out whats in those pigments, learn their composition, and that requires lab work - detective work really - in a word, Spectroscopy. So, how do we use Spectroscopy? Well, we put an infrared microscope - a spectroscope - on tiny tiny bits of paint. And using ultraviolet lig
12、ht we can see thespectral signature of each component part of the pigment. Then we compare these signatures with those of particular elements like zinc or lead, to determine what the pigment was made of. So, you can see why this type of analysis requires a knowledge of the history of pigments, right
13、? How and when they were made? Say we determined a pigment was made with zinc, for example. We know the spectral signature of zinc. And it matches that of the paint sample. We also know that zinc wasnt discovered until the 18th century. And since Rembrandt lived during the 17th century, we know he c
14、ouldnt have painted it. Now, Spectroscopy has a very distinct advantage over previous methods of analyzing our works, because its not invasive. You dont have to remove big chips of paint to do your analysis, which is what other methods require. All you do is train the microscope on tiny flecks of pa
15、int and analyze them.Now a word or two about restoration. Sometimes original art works appear questionable or inauthentic because theyve had so many restorers add touch-up layers to cover up damage, damage from the paint having deteriorated over time. Well, spectroscopy can reveal the composition of
16、 those touch-up layers too. So we can find out when they were applied. Then if we want to undo some bad restoration attempts, we can determine what kind of process we can use to remove them to dissolve the paint and uncover the original. 化学 旁白：请听化学课上的一篇演讲 教授：好的，我知道你们对此次的实验作业都有很多问题，因此今 天早上我将花点时间跟你们讨论一下。那么，你们知道此次作业是跟光 谱学有关的，是吧？你们通过阅读应该能够很好了解这个概念。但是， 我们还是将一些基本要点过一遍吧。什么是光谱学呢？嗯，我能给你们 的最简单的定义就是，光谱学是关于物和光之间相互作用的研究。这样 ，可见光拥有不同颜色和波长，聚在一起就成了我们做说的光谱。光谱是一条五颜六色的缎带，就像你
