Advantages of electron microscopes
Scanning transmission electron microscopy was developed in the 1950s. Instead of light, TEM uses a focused beam of electrons, which is sent through a sample to form an image. The advantage of transmission electron microscopy over light microscopy is that it is able to produce greater magnification that optical microscopes cannot reveal details.
How the Microscope Works
Transmission electron microscopes work similarly to light microscopes, but instead of light or photons, they use beams of electrons. An electron gun is like a light source in an optical microscope, a source of electrons and functions. Negatively charged electrons are attracted to the , and the ring carries a positive charge. A magnetic lens focuses the stream of electrons as they travel through the vacuum inside the microscope. These focused electrons strike the specimen on the stage and bounce off the specimen, creating x-rays in the process. The returned, or scattered, electrons, as well as X-rays, are converted into a signal that feeds an image onto a television screen for the scientist's views of the specimen.
Advantages of Transmission Electron Microscopy
Samples of thin sections for optical microscopy and transmission electron microscopy. Interestingly, it magnifies specimens to a greater degree than a light microscope. Magnifications of 10,000 times or more are possible, allowing scientists to see of very small instructors. cells, such as mitochondria and organelles, are clearly visible. The crystal structure of TEM specimens provides excellent resolution and can even reveal the arrangement of atoms within the sample.
Limitations of Transmission Electron Microscopy
Transmission electron microscopy requires the specimen to be in a vacuum chamber. Because of this requirement, the microscope can be used to observe living specimens, such as protozoa. Some delicate samples may also be damaged by the electron beam and must first be chemically stained or coated to protect them. This treatment sometimes destroys the specimen.
Ordinary microscopes use focused light to magnify the image, but they have a built-in physical limit of about 1000x magnification. This limit was reached in the 1930s, but the scientists hope to increase their magnification potential, allowing them to probe the inner workings cells and other microscopic structures.
In 1931, Max Noel and Ernstruska developed the first transmission electron microscope. Due to the complexity of the microscope's necessary electronic instrumentation, scientists did not have the first commercial transmission electron microscope until the mid-1960s.
