The Principles and Limitations of Transmission and Scanning Electron Microscopes

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The Principles and Limitations of Transmission and Scanning Electron Microscopes Introduction Microscopy has a major role in cytology.From the very beginning researchers have tried to develop ways of looking directly at living cells.This examination has revealed much about the morphology of cells and tissues.In recent years,development in microscopes,dyes,staining and preparatory techniques have helped reveal even more about the structure and function of cells.Microscopes have a certain magnification and resolving power.In any microscope the the resolving power is more important than the magnification.The resolving power of a microscope is the least distance between two objects where the…show more content…
be examined by light microscopy must be sufficiently transparent and thin enough for light to pass through .They are cheap,portable and easy to handle.However they cannot resolve anything that is less than 0.2 micro metre apart This limit is due to the wavelength of light.For this reason they can't examine minute organisms like viruses nor can they readily allow scientists to examine individual tiny parts of cells in detail.It has low resolution(200nm) and low magnification.(X1500).Howver light microscopes only allow us to determine the shape of whole cells or large organelles.It does not let us see smaller organelles.Those which are visible lack clarity (appear fuzzy).Hence the magnification is less important than the resolution.The low resolution of light microscopes is due to the low wavelength of light (500nm) Principles and Limitations of electron microscopy The other type of microscope is the electron microscope (which consists of transmission electron microscope and scanning electron microscope).It works by focussing a beam of electrons at the specimen.The electrons have a higher wavelength than photons of light hence the resolving power is greater.The beam of electrons are produced by a heated filament ,focussed on the specimen by the condenser lens and the image then magnified by the objective and projector lenses.The beam can be bent and focussed by electromagnetic

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