Transmission electron microscopy, Biology

Assignment Help:

Transmission electron microscopy:

Around 1931-32 two German scientists. Knoll and Ruska. Invented transmission electron microscopy, and built the first transmission electron microscope (TEM) in 1938 .Hillier 1940 built a high resolution TEM. A strong beam of electrons, issued from tungsten filaments, passed through vacuum  and focussed by electromagnets, producing a radiation wavelength   of about 0.0005nm is used to  illuminate objects in this electrons  strike against a fluorescent screen, or directly fall onto a photographic film, producing an electron micrograph. A practical resolution of about 5 a and magnification of one to several hundred thousand have been achieved by this  microscopy, combined with modern cytological techniques, this microscopy has enabled scientists to know of many  finer details of cell structure down to the macromolecular level. This knowledge of ultra structure or sub microscopic structure of the cell has resulted into the establishment of Molexular Biology.

Knoll (1935) demonstrated the feasibility of scanning electron microscopy achieving a resolution of about 30 a for three dimensional study of surface topography of objects in considerable details. Von Adrienne (1938) built first scanning electron microscope (SEM) .It is smaller and simpler than TEM. Electrons used SEM does not pass through the object, but are simply scattered from the surface of the object.              


Related Discussions:- Transmission electron microscopy

Define role of nutrients in controlling gene expression, Define Role of Nut...

Define Role of Nutrients in Controlling Gene Expression? The role of several nutrients in controlling gene expression, as mentioned earlier, is in infancy, but with advancing b

Explain difference between an ecological niche and a habitat, What is the d...

What is the difference between an ecological niche and a habitat? An ecological place is a set of peculiar activities, resources and strategies that a species explores to repro

Exstrophy of the bladder, Exstrophy of the Bladder This is the most c...

Exstrophy of the Bladder This is the most common major congenital defect of lower urinary and genital tract. This is found more frequently in males than in females. Exstr

What do all organic compounds contain, What do all organic compounds contai...

What do all organic compounds contain? The key element is carbon. Organic compounds are all carbon-having compounds. By definition, an organic compound having carbon. Alt

Which terrestrial vertebrate group is extremely rare deserts, Which terrest...

Which terrestrial vertebrate group is extremely rare in deserts? The Amphibians are terrestrial vertebrates very rare in desert environments (although there are a few species a

Temperate shrublands, These are areas where woody shrubs predominate rather...

These are areas where woody shrubs predominate rather then trees. In regions with a Mediterranean type of climate i .e., hot dry summers and cool wet winters, shrubs grow close tog

What is the advantage of the double and complete circulation, How many cham...

How many chambers do the bird heart and the mammalian heart have? Concerning temperature maintenance what is the advantage of the double and complete circulation of these animals?

Determine the muscular-skeletal system, Determine the Muscular-Skeletal Sys...

Determine the Muscular-Skeletal System It is known we all do movement and these take place by movement of muscles in coordination with the skeletal system. In human body muscle

Lorica - body form protozoans, Lorica - body form Protozoans It is a c...

Lorica - body form Protozoans It is a covering which unlike the theca fits loosely around the organism. It is a cup, bell or vase-like structure with one opening through which

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd