您可能在教室或科学实验室中找到的常用显微镜类型是光学显微镜。光学显微镜使用光来放大图像高达2000倍(通常更低),分辨率约为200纳米。另一方面,电子显微镜使用电子束而不是光来形成图像。电子显微镜的放大率可高达10,000,000x,分辨率为50皮米(0.05纳米)。在光学显微镜上使用电子显微镜的优点是更高的放大率和分辨率。缺点包括设备的成本和尺寸,制备用于显微镜和使用显微镜的样品的特殊训练的需要,以及需要在真空中观察样品(尽管可以使用一些水合样品)。理解电子显微镜如何工作的最简单方法是将其与普通光学显微镜进行比较。在光学显微镜中,您可以通过目镜和镜头观察样品的放大图像。光学显微镜设置包括样品,透镜,光源和您可以看到的图像。在电子显微镜中,电子束取代了光束。样品需要专门准备,以便电子可以与之相互作用。样品室内的空气被抽出以形成真空,因为电子不会在气体中传播很远。电磁线圈不是透镜,而是聚焦电子束。电磁铁弯曲电子束的方式与镜头弯曲的方式大致相同。图像是由电子产生的,因此可以通过拍照(电子显微镜照片)或通过监视器观察样本来观察。有三种主要类型的电子显微镜,它们根据图像的形成方式,样品的制备方式和图像的分辨率而不同。这些是透射电子显微镜(TEM),扫描电子显微镜(SEM)和扫描隧道显微镜(STM)。

美国斯坦福大学物理学Essay代写:电子显微镜

The usual type of microscope you might find in a classroom or science lab is an optical microscope. An optical microscope uses light to magnify an image up to 2000x (usually much less) and has a resolution of about 200 nanometers. An electron microscope, on the other hand, uses a beam of electrons rather than light to form the image. The magnification of an electron microscope may be as high as 10,000,000x, with a resolution of 50 picometers (0.05 nanometers). The advantages of using an electron microscope over an optical microscope are much higher magnification and resolving power. The disadvantages include the cost and size of the equipment, the requirement for special training to prepare samples for microscopy and to use the microscope, and the need to view the samples in a vacuum (although some hydrated samples may be used). The easiest way to understand how an electron microscope works is to compare it to an ordinary light microscope. In an optical microscope, you look through an eyepieces and lens to see a magnified image of a specimen. The optical microscope setup consists of a specimen, lenses, a light source, and an image that you can see. In an electron microscope, a beam of electrons takes the place of the beam of light. The specimen needs to be specially prepared so the electrons can interact with it. The air inside the specimen chamber is pumped out to form a vacuum because electrons don’t travel far in a gas. Instead of lenses, electromagnetic coils focus the electron beam. The electromagnets bend the electron beam in much the same way lenses bend light. The image is produced by electrons, so it is viewed either by taking a photograph (an electron micrograph) or by viewing the specimen through a monitor. There are three main types of electron microscopy, which differ according to how the image is formed, how the sample is prepared, and the resolution of the image. These are transmission electron microscopy (TEM), scanning electron microscopy (SEM), and scanning tunneling microscopy (STM).

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