The electron microscope is a very powerful microscope which can see things that normal microscopes cannot. There are 2 types of electron microscope: the transmission electron microscope and the scanning electron microscope. The sample must be in a vacuum so that no air bubbles are on the produced image and also because the electrons are absorbed by the molecules in the air, this means that the electron microscope cannot be used to look at living cells. The tissue is soaked in alcohol to dehydrate it and must be stained in order to improve the contrast on the image produced called an electronmicrograph. To see the objects you need to use radiation with a shorter wavelength, this is done by getting metal very hot so that some of its electrons gain enough energy to escape from their orbits. The escaped electrons behave like electromagnetic radiation but have a very short wavelength. Electrons are negatively charged the microscope uses electromagnets to focus the image on to a fluorescent screen. Increasing the magnification in electron microscopy will result in an increase in the amount of visible detail. So the resolving power of the microscope depends on the wavelength of the electromagnetic radiation. The Transmission Electron Microscope
The transmission electron microscope is used to look inside cells and allows us to see separate structures, particles which are as close together as 2 nanometres (the resolution). Increasing the magnification in electron microscopy will result in an increase in the amount of visible detail Electrons must be able to pass through the specimen and this means that part of the specimen appears bright but other parts absorb the electrons so they are electron-dense areas and therefore appear dark on the image. A problem with the microscope is that the cells must be cut into very thin sections using a knife made of glass. The cut tissue has to be about the thickness of the film around a soap bubble. Another problem...
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