『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 38 Passage 1阅读练习：According to paragraph 5, what is the role of metal in the scanning electron microscope?真题题目及答案解析，TPO/Official 38 Passage 1阅读原文范文音频翻译

托福TPO/Official 38 Passage 1阅读原文According to paragraph 5, what is the role of metal in the scanning electron microscope?题目答案及解析-新东方托福官方网校手机版

在十七世纪首次使用显微镜之前，没有人知道生物是由细胞组成的。

Before microscopes were first used in the seventeenth century, no one knew that living organisms were composed of cells.

第一批显微镜是光学显微镜，其工作原理是使可见光穿过标本。

The first microscopes were light microscopes, which work by passing visible light through a specimen.

显微镜中的玻璃透镜使光线弯曲以放大样品的图像，并将图像投影到观察者的眼睛或摄影胶片上。

Glass lenses in the microscope bend the light to magnify the image of the  specimen and project the image into the viewer’s eye or onto photographic film.

光学显微镜最多可将物体放大1000倍而且不会造成模糊。

Light microscopes can magnify objects up to 1,000 times without causing blurriness.

放大倍率是指物体表观尺寸的增加，它是显微镜检查中的重要因素之一。

Magnification, the increase in the apparent size of an object, is one important factor in microscopy.

同样重要的是分辨率，即图像清晰度的度量。

Also important is resolving power, a measure of the clarity of an image.

分辨率是光学仪器将两个物体分开显示的能力。

Resolving power is the ability of an optical instrument to show two objects as separate.

例如，可以借助望远镜将肉眼看起来像天空中的单颗恒星分解为两颗恒星。

For example, what looks to the unaided eye like a single star in the sky may be resolved as two stars with the help of a telescope.

任何光学设备都受到其分辨率的限制。

Any optical device is limited by its resolving power.

光学显微镜无法分辨小于0.2微米的细微物质，大约是最小细菌的大小。因此，无论将这种细菌的图像放大多少倍，光学显微镜都无法显示细胞内部结构的细节。

The light microscope cannot resolve detail finer than 0.2 micrometers, about the size of the smallest bacterium; consequently, no matter how many times its image of such a bacterium is magnified, the light microscope cannot show the details of the cell’s internal structure.

从1665年英国显微学家罗伯特·胡克发现细胞开始，直到二十世纪中叶，生物学家只有用光学显微镜才能观察细胞。

From the year 1665, when English microscopist Robert Hooke discovered cells, until the middle of the twentieth century, biologists had only light microscopes for viewing cells.

但是他们发现了很多东西，包括组成动植物组织的细胞，微观生物以及细胞内的某些结构。

But they discovered a great deal, including the cells composing animal and plant tissues, microscopic organisms, and some of the structures within cells.

到十九世纪中叶，这些发现引发了细胞理论，该理论指出所有生物都是由细胞组成的，并且所有细胞都来自其他细胞。

By the mid-1800s, these discoveries led to the cell theory, which states that all living things are composed of cells and that all cells come from other cells.

随着生物学家在二十世纪五十年代开始使用电子显微镜，我们对细胞结构的了解有了巨大的飞跃。

Our knowledge of cell structure took a giant leap forward as biologists began using the electron microscope in the 1950s.

电子显微镜使用电子束代替光，并且具有比光学显微镜更高的分辨率。

Instead of light, the electron microscope uses a beam of electrons and has a much higher resolving power than the light microscope.

实际上，最强大的现代电子显微镜可以分辨小至0.2纳米的物体，比光学显微镜提高了一千倍。

In fact, the most powerful modern electron microscopes can distinguish objects as small as 0.2 nanometers, a thousandfold improvement over the light microscope.

这句话结尾句号的直径比直径为0.2纳米的物体（大原子的大小）大100倍。

The period at the end of this sentence is about a million times bigger than an object 0.2 nanometers in diameter, which is the size of a large atom.

电子显微镜只有在特殊条件下才能检测单个原子。

Only under special conditions can electron microscopes detect individual atoms.

但是，细胞，细胞器甚至DNA和蛋白质等分子都比单个原子大得多。

However, cells, cellular organelles, and even molecules like DNA and protein are much larger than single atoms.

生物学家使用扫描电子显微镜研究细胞表面的详细结构。

Biologists use the scanning electron microscope to study the detailed architecture of cell surfaces.

它使用电子束扫描已涂有金属的一个或一组细胞的表面。

It uses an electron beam to scan the surface of a cell or group of cells that have been coated with metal.

The metal stops the beam from going through the cells.

当金属被电子束撞击时，它会发射电子。

When the metal is hit by the beam, it emits electrons.

电子被聚焦形成细胞外部的图像。

The electrons are focused to form an image of the outside of the cells.

扫描电子显微镜产生的图像看起来是三维的。

The scanning electron microscope produces images that look three-dimensional.

另一方面，透射电子显微镜用于研究内部细胞结构的细节。

The transmission electron microscope, on the other hand, is used to study the details of internal cell structure.

样品被切成非常薄的切片，透射电子显微镜将电子束对准一个切片，就像光学显微镜将光束穿过样品一样。

Specimens are cut into extremely thin sections, and the transmission electron microscope aims an electron beam through a section, just as a light microscope aims a beam of light through a specimen.

但是，与所有电子显微镜一样，透射电子显微镜不是使用玻璃制成的透镜，而是使用电磁体作为透镜。

However, instead of lenses made of glass, the transmission electron microscope uses electromagnets as lenses, as do all electron microscopes.

电磁体使电子束弯曲以放大图像并将其聚焦到显示屏或胶卷上。

The electromagnets bend the electron beam to magnify and focus an image onto a viewing screen or photographic film.

电子显微镜确实彻底改变了细胞和细胞器的研究。

Electron microscopes have truly revolutionized the study of cells and cell organelles.

尽管如此，它们还没有取代光学显微镜。

Nonetheless, they have not replaced the light microscope.

电子显微镜的一个问题是它们不能用于研究活体标本，因为标本必须保持在真空室内。也就是说，必须除去所有的空气和液体。

One problem with electron microscopes is that they cannot be used to study living specimens because the specimen must be held in a vacuum chamber; that is, all the air and liquid must be removed.

对于研究生命过程（例如细菌的旋转运动）的生物学家来说，配备摄像机的光学显微镜可能比扫描电子显微镜或透射电子显微镜都更好。

For a biologist studying a living process, such as the whirling movement of a bacterium, a light microscope equipped with a video camera might be better than either a scanning electron microscope or a transmission electron microscope.

因此，光学显微镜仍然是有用的工具，特别是对于研究活细胞而言。

Thus, the light microscope remains a useful tool, especially for studying living cells.

细胞的大小通常决定了生物学家用来研究它的显微镜的类型。

The size of a cell often determines the type of microscope a biologist uses to study it.

According to paragraph 1, what happens to the light when a specimen is being viewed with a light microscope?

Why does the author mention “a telescope” as part of the discussion of microscopes?

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information.

What can be inferred from paragraph 3 about the scientific contribution of Robert Hooke?

The word “giant” in the passage is closest in meaning to

According to paragraph 4, which of the following is true of electron microscopes?

The word “detect” in the passage is closest in meaning to

According to paragraph 5, what is the role of metal in the scanning electron microscope?

The word “emits” in the passage is closest in meaning to

According to paragraphs 5 and 6, the transmission electron microscope differs from the scanning electron microscope in all of the following ways EXCEPT:

The word “Nonetheless” in the passage is closest in meaning to

Look at the four squares  that indicate where the following sentence could be added to the passage. Live organisms, therefore, would not survive while being observed with an electron microscope.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

Directions: Select from the seven sentences below the three sentences that correctly characterize light microscopes and the two sentences that correctly characterize electron microscopes. Drag each sentence you select into the appropriate column of the table. Two of the sentences will NOT be used. This question is worth 3 points.

Microscopes Before microscopes were first used in the seventeenth century, no one knew that living organisms were composed of cells. The first microscopes were light microscopes, which work by passing visible light through a specimen. Glass lenses in the microscope bend the light to magnify the image of the specimen and project the image into the viewer’s eye or onto photographic film. Light microscopes can magnify objects up to 1,000 times without causing blurriness. Magnification, the increase in the apparent size of an object, is one important factor in microscopy. Also important is resolving power, a measure of the clarity of an image. Resolving power is the ability of an optical instrument to show two objects as separate. For example, what looks to the unaided eye like a single star in the sky may be resolved as two stars with the help of a telescope. Any optical device is limited by its resolving power. The light microscope cannot resolve detail finer than 0.2 micrometers, about the size of the smallest bacterium; consequently, no matter how many times its image of such a bacterium is magnified, the light microscope cannot show the details of the cell’s internal structure. From the year 1665, when English microscopist Robert Hooke discovered cells, until the middle of the twentieth century, biologists had only light microscopes for viewing cells. But they discovered a great deal, including the cells composing animal and plant tissues, microscopic organisms, and some of the structures within cells. By the mid-1800s, these discoveries led to the cell theory, which states that all living things are composed of cells and that all cells come from other cells. Our knowledge of cell structure took a giant leap forward as biologists began using the electron microscope in the 1950s. Instead of light, the electron microscope uses a beam of electrons and has a much higher resolving power than the light microscope. In fact, the most powerful modern electron microscopes can distinguish objects as small as 0.2 nanometers, a thousandfold improvement over the light microscope. The period at the end of this sentence is about a million times bigger than an object 0.2 nanometers in diameter, which is the size of a large atom. Only under special conditions can electron microscopes detect individual atoms. However, cells, cellular organelles, and even molecules like DNA and protein are much larger than single atoms. Biologists use the scanning electron microscope to study the detailed architecture of cell surfaces. It uses an electron beam to scan the surface of a cell or group of cells that have been coated with metal. The metal stops the beam from going through the cells. When the metal is hit by the beam, it emits electrons. The electrons are focused to form an image of the outside of the cells. The scanning electron microscope produces images that look three-dimensional. The transmission electron microscope, on the other hand, is used to study the details of internal cell structure. Specimens are cut into extremely thin sections, and the transmission electron microscope aims an electron beam through a section, just as a light microscope aims a beam of light through a specimen. However, instead of lenses made of glass, the transmission electron microscope uses electromagnets as lenses, as do all electron microscopes. The electromagnets bend the electron beam to magnify and focus an image onto a viewing screen or photographic film. Electron microscopes have truly revolutionized the study of cells and cell organelles. Nonetheless, they have not replaced the light microscope.  One problem with electron microscopes is that they cannot be used to study living specimens because the specimen must be held in a vacuum chamber; that is, all the air and liquid must be removed.  For a biologist studying a living process, such as the whirling movement of a bacterium, a light microscope equipped with a video camera might be better than either a scanning electron microscope or a transmission electron microscope.  Thus, the light microscope remains a useful tool, especially for studying living cells.  The size of a cell often determines the type of microscope a biologist uses to study it.