Compare Transmission Electron Microscopes (TEMs) with Scanning Electron Microscopes (SEMs)
Short answer to "compare TEMs with SEMs":
Key differences between micrographs produced by TEMs and SEMs can be divided into aspects in which TEM micrographs are generally more useful and respects in which SEM micrographs are generally more useful.
Advantages of TEMs over SEMs
Advantages of SEMs over TEMs
A TEM might be used in preference to an SEM because:
An SEM might be used in preference to a TEM because:
What if both 3D images and the highest possible resolution and magnification are required ?
In some cases it is useful to study both transmission electron micrographs and scanning electron micrographs of the same tissue or material. In that case it would be necessary to prepare appropriate samples for each of these types of electron microscope.
A more detailed comparison betweeen TEMs and SEMs might include lists of the similarities and differences between TEMs and SEMs. The main differences between these types of electron microscopes are stated in the table above. A list of similarities between TEMs and SEMs is similar to the list of differences between light microscopes and electron microscopes but simpler to write because there is no need to mention light microscopes when identifying some of the many things TEMs and SEMs have in common, e.g.
List of features electron microscopes generally have in common with each other:
- Size: Large - much larger than light microscopes.
- Radiation Type: Use beams of electrons (approx equivalent wavelength 1 nm).
- Control of image formation : Beams of electrons are focused using electromagnets due to negative charge on electrons.
- Resolution: Electron microscopes have much higher resolution than light microscopes due to the shorter equivalent wavelength of electron beams compared with visible light.
- Magnification: Electron microscopes have much higher magnification than light microscopes. This is due to the shorter equivalent wavelength of electron beams compared with visible light.
- Colour Images: Electron microscopes produce greyscale images. However, "false-colour" electron micrographs are common - and can be very beautiful!
- Preparation of specimens : Generally involves several steps and often harsh processes, e.g. using corrosive chemicals. Appropriate skill is needed both to prepare specimens and to interpret electron micrograph images due to "artefacts" in images. (Artefacts are features in images that are not present in the specimen but rather are due to the processes used to prepare the specimen and produce the image.)
- Image Formation : Unlike light microscope images, which can be viewed directly, electron microscopes including TEMs and SEMS require use of an interface such as a fluorescent screen, photographic plate or electronic display. This is because electrons cannot be observed directly by the human eye.
- Usage Limitations : Living specimens cannot be viewed using electron microscopes because electron microscopes require there to be a vacuum in the tube - otherwise the electrons would be absorbed by air molecules.
Microscopes mentioned in school biology:
- Light Microscope
(used in classrooms & college laboratories)
- Electron Microscopes
* Scanning Electron Microscope (SEM)
* Transmission Electron Microscope (TEM)
Read more about: What is light ?
Transmission Electron Microscopes (TEMs) and Scanning Electron Microscopes (SEMs) are just two of the many types of microscopes used for a wide range of scientific applications. General examples of uses include:
- for diagnosis (based on analysis of diseased tissues) in medicine and veterinary medicine
- medical research including the development and testing of new drugs
- study of materials - living or otherwise - in other sciences such as archeology, metallurgy, botany, zoology
- development and testing of new materials for use in industry.