• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Describe the principles and limitations of transmission and scanning electron microscopes. Specific reference should be made to magnification and resolution

Extracts from this document...


Describe the principles and limitations of transmission and scanning electron microscopes.Specific reference should be made to magnification and resolution 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 microscope can still distinguish the objects as being separate.It is a measure of detail that can be seen.A microscope with a high resolving power enables us to view images with a high resolution.With a low resolution they would be viewed as one object.Microscopes with a high magnification are only able to increase the size of the object that is being viewed.The resolution will be the same.(ie the object will still lack clarity and appear fuzzy).The two types of microscopes are electron and light microscopes. ...read more.


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 lenses,in the same way the glass lenses are used in a light microscope.Unlike light microscopes ,the electron microscopes,have a high resolution(0.1 nm) and high magnification(1000000X) .The image formed by the electron microscope is projected onto a cathode ray tube so that it is visible to the operator ,looking rather like a black and white TV screen. The second type is the scanning electron microscope.They examine the surface of specimens.The surface is coated with a film of gold and palladium.A fine beam of electrons is passed backwards and forwards over the specimen.and the electrons that are reflected from it are collected and amplified to form an image on a cathode ray tube.Although the scanning electron microscope gives a much lower resolution(5-20nm) ...read more.


Conclusion Electron microscopes have been far more successful in determining cell ultrastructure compared to light microscopes.The high magnification and high resolution enables us to see cells and organelles much bigger and in much more detail.It has brought about the complete reappraisal of the microanatomy of biological tissues,organisms and cells.In early days of it's applications to biological materials,it was a tool of anatomists and histologists.The detailed knowledge of internal organisation of organelles has helped in our understanding of how they work.The fact that electron micrographs appear in many research papers and books in cell biology and anatomy emphasize the importance of electron microscopy to the biologists not only in the present times but also in future.Today electron microscopy is widely used in metallurgy,biology,material science,physics,chemistry and many other biological fields.It has been an integral part in the understanding of the complexities of cellular structure,the fine structure of metals and crystalline materials as well as numerous other areas of the microscopic world.Although new inventions like the laser microscope may seem to put the use of electron microscopes under threat they will always play an integral part in determining the ultrastructure of cells. ?? ?? ?? ?? 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Microscopes & Lenses section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Here's what a star student thought of this essay

3 star(s)

Response to the question

The candidate has used headings to split up the sections of information, which is fine, though their introduction is unclear and it reads more like a secondary paragraph. It is often easier to leave your introduction until last, that way ...

Read full review

Response to the question

The candidate has used headings to split up the sections of information, which is fine, though their introduction is unclear and it reads more like a secondary paragraph. It is often easier to leave your introduction until last, that way you can make it clear to the reader exactly what your plan to discuss, which is the main point of your introduction. You also need to include a brief description of you topic, in this case you should describe what a microscope is and what it used for. As the title of this essay is ‘Describe the principles and limitations of transmission and scanning electron microscopes’ it is strange that the candidate starts off by discussing optical microscopes, this actually left me feeling quiet confused about the purpose of this essay. This is another reason why it is so important to state what you plan to discuss in your introduction.

Level of analysis

The candidate gives a reasonable amount of detail on each type of microscope and they have clearly discussed the limitations for each. However they could have made the this essay more interesting to read by providing diagrams or images of the microscopes, by doing this you can refer to the images when discussing specific parts such as lens and this can help the reader understand what you are talking about. In addition to this the candidate could also have taken the time to undergone independent research, perhaps on the history of the microscope and how they were developed, this extra information shows interest in your subject and can make the essay more enjoyable to read. Finally, though the candidate has written a suitable conclusion, they have failed to summarise their key points, this is useful as it helps to tie together any lose ends and bring the essay to a close. In addition to this you are more likely to leave the reader with a good impression of your work if you write a personal reflection into your conclusion, this is because your teacher/examiner is interested in what you have to say and what you have learnt by writing your essay.

Quality of writing

The quality of the writing in this essay is only average, at times it is difficult to read and it feels more like an amalgamation of facts, therefore the essay does not flow as well as it could. You could improve this by taking the time to write out a plan and carefully thinking about what you want to say, it is also important to make sure that you spilt your writing up in paragraphs, do no simply write everything on one topic into a single paragraph, the general rule of thumb is that you should start a new paragraph when you begin discussing a new point/idea. In addition to this there are one or two spelling errors which could have been avoided had the candidate taken the time to carefully proof read their work.

Did you find this review helpful? Join our team of reviewers and help other students learn

Reviewed by pictureperfect 26/07/2012

Read less
Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Microscopes & Lenses essays

  1. Peer reviewed

    An Essay about Microscopes

    3 star(s)

    through the specimen (like the slide). Whatever part is transmitted is projected onto a phosphor screen for the user to see. The Scanning Electron microscope is the most modern type of microscope this scanning electron microscope has a magnification range from 15x to 200,000x (reached in 25 steps)

  2. Peer reviewed

    Electron microscopes.

    3 star(s)

    The tissue is soaked in alcohol to dehydrate it. The tissue is then preserved using substances, which prevent enzyme action i.e. embedded in resin to make it hard this is to avoid it releasing any gases or vapours, which might hinder the clarity of the specimen. This might introduce artefacts.

  1. Electron Microscopy

    For larger specimens, the specimen is either placed in a vacuum chamber and split along the lines of least resistance, or the freeze fracture technique is used.

  2. To investigate the relationship between the distance between a lens and an object, and ...

    Evaluation: There are a number of possible problems with this experiment that may have caused the deviation of the results from the predicted ones. For example, the angle of the lens in the holder may have varied. This would cause the refraction to be different an would thus influence the results.

  1. My experiments focus is to obtain an accurate measurement for a specific lenss power.

    The result is a more defined image. * Wooden Ruler: The ruler was used to measure the U (distance between light source and lens) values and V (distance between lens and where image is formed) values. It has a resolution of 1mm and therefore creates an uncertainty of +/- 0.5mm in my 'U' measurements.

  2. In this experiment I will be investigating the efficiency of a motor. I hope ...

    Adding each weight gradually, having recordings for each weight 3 times therefore diving the error by three. Voltmeter and Ammeter flickers therefore less accurate. Therefore more likely to obtain anomalous results. Resistance in leads cause possible errors as less accurate measurements of voltage and current.

  1. Explain how the electron microscope has affected our knowledge of cell form and structure

    Fixation and dehydration using alcohol. 2. Embedding in resin which is hardened in an oven. 3. Sectioning using an ultramicrotome and a glass knife. 4. Mounting on a copper grid to give support (electrons cannot pass through glass). 5.

  2. How does a microscope work?

    4 X 10 = 40 11. 10 X 10 = 100 15. 40 X 10 = 400 Conclusions The purpose was achieved. Since the enlargement of images under certain magnifications using the lenses and light of a microscope was seen, it can therefore be concluded that a microscope enables one

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work