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If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. While transmission electron microscopes (TEMs) continue to become more accessible thanks to novel automation, easy-to-use software, and decreasing space requirements, they can still be quite intimidating for new users who have never worked with an electron microscope before. They may be surprised to learn, however, that these
instruments are not too different from the familiar light microscope. To understand how, let’s begin by considering the light microscope, shown below. In a light, or optical, microscope, a light source is placed below the sample, which must be thin enough to allow some light to pass through. (If it isn’t, the object will appear dark, and no details can be discerned.) The light is focused onto the sample with a condenser lens, resulting in a focused
point of light on the specimen’s surface. As the white light interacts with the sample it is modified by its molecules, which selectively absorb or reflect only certain kinds of light. This results in the color and contrast information that makes up the image. Lenses then modify this projected information into a magnified image that we perceive with our eyes. Diagram of a light microscope with key elements highlighted. Electron microscope descriptionIn an electron microscope, an electron beam takes the place of the light source. Due to the wave-particle duality of electrons in a vacuum, they can behave just like the photons that make up light. However, electrons travel as much smaller wavelengths than visible light, enabling them to reveal smaller details than what is possible with light. Instead of a glass condenser lens, electron microscopes use electromagnetic or electrostatic lenses. These produce magnetic and electric fields that guide and focus the electrons. The sample is still positioned over a focused point of the incident beam but must now be even thinner to account for the size of the electrons. (Typical TEM sample thicknesses are around ~0.1µm, depending on the material.) Just like the optical microscope, the electron beam interacts with the sample atoms, carrying away contrast and compositional information. As our eyes are incapable of perceiving electrons, it is no longer sufficient to have them serve as the detector. Instead, special electron imaging devices convert the electron signal into a greyscale image, where contrast corresponds to differences in sample thickness and density.  Side-by-side comparison of a TEM and an optical microscope, with analogous parts connected. Note that the light microscope has been inverted to more clearly parallel the TEM structure. Summary of instrument comparisonOverall, while there are different principles controlling and guiding the incident beam for both instruments, the process of image generation is broadly the same. A beam interacts with the sample and passes through to the other side; the changes in beam energy correspond to different features in the final image. Hopefully this quick comparison has dispelled some of the initial intimidation that electron microscopes pose, empowering you to pursue the unparalleled information that electron microscopy provides. Luckily, the latest generation of cryo-transmission electron microscopes (cryo-TEMs) includes more affordable, easier-to-use tools. In late 2020, we introduced the Thermo Scientific Tundra Cryo-TEM which includes several features that improve usability and empower anyone to use cryo-EM, even researchers who are new to the technique. Learn more about the Tundra Cryo-TEM >> Alex Ilitchev, PhD, is a Scientific Content Writer at Thermo Fisher Scientific. // To learn more about electron microscopy for Life Sciences, please visit our Learning Center.
Image Credit: anyaivanova/Shutterstock.com Microscopy visualizes structures that are too small to see with the human eye, but that is about all light microscopy and electron microscopy have in common. Light microscopy uses visible light or photons to illuminate a sample, while electron microscopy uses electrons, as the name suggests. Each technique has its advantages and disadvantages, discussed below. How Does Light Microscopy Work?The oldest of microscopy techniques, light microscopy, uses visible light and lenses to create a small object's magnified image. Basic light microscopes can be very simple e.g., a magnifying glass, and use one or several lenses for magnification. Compound light microscopes are more complex, using a system of lenses, with one set to enlarge the other's image to achieve higher resolution and sample contrast. Samples can be illuminated from below, or light can pass through or around the objective lens (the lens closest to the sample). Light microscopes are particularly useful in biology to observe living cells and their biological activity, the uptake of food, cell division, and movement. In vivo staining helps to examine the uptake of colored pigments by cells as images often in color. Related Stories
Light microscopes are relatively low cost, and samples require very little preparation – anything from a few minutes to a few hours. This means they are widely used in microelectronics, nanophysics, biotechnology, pharmaceutic research, mineralogy, microbiology, and medical diagnostics. However, light microscopy can only magnify structures by around 1000 to 2000 times as the wavelength of visible light limits it. Electron microscopy was designed to overcome this limitation, set by the diffraction limit of visible light. Seeing Smaller with Electron MicroscopyElectron microscopes use a beam of accelerated electrons as a source of illumination and a shaped magnetic field to form electron-optical lens systems equivalent to the glass lenses of light microscopes. The original electron microscopes were transmission electron microscopes (TEM), which use a high-voltage beam from an electron gun to illuminate the sample. The electrons travel through a thin section of the sample to generate a 2D cross-sectional image. There are many variations of electron microscopes, including scanning electron microscopes (SEM) which probe a sample with a focused electron beam to create a 3D image of the surface of a sample, rather than the interior, reflection emission microscopy (REM), and scanning tunneling emission microscopy (STEM). Electron microscopy offers a better resolution than light microscopes and can reveal the structure of smaller objects not usually seen by the latter. This is because the wavelength of electrons is up to 100,000 shorter than visible light photons. Electron microscopes have a high resolving power, 250 times that of light microscopes, and magnify objects by 100,000 to 300,000 times. Electron microscopes are used in biology and life sciences, materials research, and industry, often in quality control or failure analysis. They are utilized to view the ultra-structures of several biological and inorganic specimens such as microorganisms, cells, large molecules, biopsy samples, metals, and crystals. However, the technique can only be used to analyze dead or dry samples, meaning it is impossible to view living things' small structures. Consequently, sample preparation can take days and can involve chemical fixation, negative staining, cryofixation, dehydration, and sectioning. These microscopes can also only operate under a vacuum, making them expensive to build and maintain. They are also large and require more training for effective operation. The resulting image is in black and white/greyscale. They are often false-colored to highlight structures or aesthetic reasons, but they do not reveal any additional information. The Better Choice?Each microscope has advantages and disadvantages; which one you chose will depend on the investigation. Anything involving living things will mean selecting a light microscope because the electron beam's high radiation will likely kill the specimen. But if you are looking at a dry or dead sample, an electron microscope will offer much higher resolution, and therefore more detail. References and Further ReadingAryal, S. (2018) Differences between Light Microscope and Electron Microscope, microbiologyinfo.com https://microbiologyinfo.com/differences-between-light-microscope-and-electron-microscope/. Accessed 3 March 2021. Microbehunter Microscopy, Electron Microscopes vs. Optical (Light) microscopes, Microbehunter Microscopy [online] http://www.microbehunter.com/electron-microscopes-vs-optical-light-microscopes/. Accessed 3 March 2021. Microscopy, The Khan Academy [online] https://www.khanacademy.org/science/high-school-biology/hs-cells/hs-introduction-to-cells/a/microscopy. Accessed 3 March 2021. Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website. What is an advantage of electron microscopes compared to light microscopes?These include: Magnification and higher resolution – as electrons rather than light waves are used, it can be used to analyze structures which cannot otherwise be seen. The resolution of electron microscopy images is in the range of up to 0.2 nm, which is 1000x more detailed than light microscopy.
What are the advantages of light microscopes What are the advantages of electron microscopes?Advantage: Light microscopes have high resolution. Electron microscopes are helpful in viewing surface details of a specimen. Disadvantage: Light microscopes can be used only in the presence of light and are costly. Electron microscopes uses short wavelength of electrons and hence have lower magnification.
What is an advantage of the electron microscope over the compound light microscope quizlet?TEM) The advantage of using electron microscopes over light microscopes is that they can magnify objects up to a million times. Also electron microscopes can produce images of much smaller objects than light microscopes can.
What are the 3 main differences between light and electron microscopes?Differences between Light Microscope and Electron Microscope. |
An advantage of electron microscopes compared to light microscopes is that electron microscopes
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