What electron microscopes are used for?
Electron microscopy (EM) is a technique for obtaining high resolution images of biological and non-biological specimens. It is used in biomedical research to investigate the detailed structure of tissues, cells, organelles and macromolecular complexes.
How do electron microscopes help us?
The development of the electron microscopes therefore helped scientists to learn about the sub-cellular structures involved in aerobic respiration called mitochondria . The scientists developed their explanations about how the structure of the mitochondria allowed it to efficiently carry out aerobic respiration.
What are the three types of electron microscopes?
There are several different types of electron microscopes, including the transmission electron microscope (TEM), scanning electron microscope (SEM), and reflection electron microscope (REM.)
How can you tell SEM from TEM?
SEM focuses on the sample’s surface and its composition whereas TEM provides the details about internal composition. Therefore TEM can show many characteristics of the sample, such as morphology, crystallization, stress or even magnetic domains. On the other hand, SEM shows only the morphology of samples.
How can you tell the difference between a TEM and a SEM image?
Summary of the main differences between a SEM and a TEM.
| SEM | TEM | |
|---|---|---|
| Image formation | Electrons are captured and counted by detectors, image on PC screen | Direct imaging on fluorescent screen or PC screen with CCD |
| Operation | Little or no sample preparation, easy to use | Laborious sample preparation, trained users required |
Why is a phosphor screen used in TEM?
A tool to visualize TEM images and diffraction patterns. A phosphor on a “fluorescent screen” is excited through electron collision. The emitted visible light produces “light and dark (contrast)” corresponding to the electron intensities to the screen. When acquiring a TEM image, the screen is raised.
What is the resolution of an light microscope?
The resolution of the light microscope cannot be small than the half of the wavelength of the visible light, which is 0.4-0.7 µm. When we can see green light (0.5 µm), the objects which are, at most, about 0.2 µm. Below this point, light microscope is not useful, as wavelength smaller than 400 nm is needed.