The way an image is formed on a electron microscope (EM) is by the electrons in an electron microscope (EM) are focused. Here the particles or the membranes in cells can be seen as separate objects if they are further apart than half of the wavelength of the beam of the electrons used. Electron microscopes have a high resolution because the electron beams have a shorter wave length. Also the other reason why biologists need a high resolution is in able to see the specimen in more detail.
The table below gives information about an electron microscopy:
The development of electron microscope (EM) has had a huge impact on biology. Due to the fact that the resolution is so high on a electron microscopy that new cell structures have been discovered.
The main disadvantage of having an electron microscope (EM) is that the electron beam must travel in a vacuum because, being so small, electrons are scattered when they hit air molecules. Therefore specimens have to be perpeared so that they retain their structure inside a vacuum.
They are two main types of electron microscope which are:
- Transmission electron microscope
- Scanning electron microscope
Firstly transmission electron microscopy (TEM) this is a beam of electrons being transmitted through the specimen. The specimen used must be a thin layer and should be stained using electron dense substances which can include substances such as heavy metal salts. These deflect the electrons in the beam and the pattern that the remaining electrons produce as they pass through the specimen is then converted into an image.
Secondly by using scanning electron microscopy (SEM’s) which are mainly used to study large three dimensional objects. Having a thin layer of a specimen will not be compulsory as instead of passing through the specimen the electron beam will bounce of the specimen. Scanning electron microscopy (SEM’s) has no resolving power, instead it is more versatile which can be used to observe many kinds of intact structures.
