Electron microscopes.

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This is the act of using electron microscopes. Electron Microscopes are scientific instruments that use a beam of highly energetic electrons to examine objects on a very fine scale. Electron microscopes can be used to view the topography (surface), the morphology (the shape and size of the particles making up the object) and also the composition (elements and compounds the object is composed of and how many: in case of cell organelles).

Electron microscopes were introduced or developed due to the limitation of light microscopes. This is because the resolving power of a microscope depends on the wavelength of the electromagnetic radiation used; because the light microscope uses only the visible part (light) of the electromagnetic spectrum whose shortest wavelength is 400 nanometre (violet light), therefore objects smaller than half of the wavelength (200nm) cannot be viewed using a light microscope. E.g. cell organelle ribosome is 20nm and can never be seen using a light microscope. As electron microscopes uses electrons, which are negatively charged and beams of electrons have a very short wavelength. This type of microscope has a very high magnification and resolution power.

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They are two major types of electron microscopes the first type originally developed: The Transmission Electron Microscope, which is quite similar to the light electron microscope just that in this case electron beams are used instead of light beams. With this type of electron microscope the beam of electrons is passed through the specimen before being viewed. Only the electrons transmitted (That is the electrons that go through the specimen) are seen. This microscope allows us to see as separate structures, particles which are as close together as 2 nanometres, thus the resolution of this microscope is about 2 nanometres. Because ...

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There are a few issues with spelling and a few incoherent sentences. This is easy to avoid if you proof read your work and make sure you use a spell check. Overall the essay is reasonably well written and shows a good level of understanding.

The candidate shows a good understanding of how electron microscopes work, they have provided a suitable level of detail and have stated the advantages and disadvantages of using this type of microscope. In addition to this the candidate has shown knowledge beyond that expected for this level of qualification as they have provided details of how specimens are prepared. This additional information is interesting for the reader and shows the candidates enthusiasm for their subject. Unfortunately the candidate has not written a conclusion, which is a mistake. A conclusion is essential to any type of essay, it gives you a chance to summarise your key points and allows you to draw the essay to close, leaving the reader with a good impression.

The candidate gives a detailed response, they clearly describe how electron microscopes are used and outline the advantages in comparison to an optic microscope. In addition to this the candidate has written a suitable introduction and states the uses of microscopes. This could be improved further my stating what they planned to discuss. It is sometimes useful to write your introduction last so that you introduce the topics you discuss.