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

What kind of exoskeleton do some molluscs present, Q. What kind of exoskele...

Q. What kind of exoskeleton do some molluscs present? Some molluscs, like gastropods and bivalves secrete an external calcareous carapace (the shell). Calcium carbonate is a fo

Explain about the rna viruses - carcinogenic, Explain about the RNA Viruses...

Explain about the RNA Viruses - carcinogenic? All oncogenic RNA viruses are retroviruses. They are of 2 types. They are acute transforming retroviruses and slow transforming re

Use values of biodiversity, Despite its importance, determining the value o...

Despite its importance, determining the value or worth of biodiversity is complex and often a cause for debate. This is largely due to the fact that the worth placed on biodiversit

The initial velocity of an enzyme catalyzed reaction, The initial velocit...

The initial velocity of  an  enzyme catalyzed reaction The mathematical relationship between  the initial velocity of  an  enzyme catalyzed reaction, the concentration of the s

Polygonum type - monosporic embryo sacs, Polygonum Type - Monosporic Embryo...

Polygonum Type - Monosporic Embryo Sacs The embryo sac is formed from the chalazal megaspore in the tetrad and is eight-nucleate. The development of the embryo sac begins with

What are main limitations on size that can be synthesized, What are main li...

What are main limitations on size that can be synthesized and how will that be change over next few years? A: Today, a 10kb gene or longer is built as part of the regular produ

What is prophylaxis, What is prophylaxis? Prophylaxis are measures take...

What is prophylaxis? Prophylaxis are measures taken to stop diseases. For instance, the use of condoms in sexual relations is a prophylaxis against contamination by agents that

Define about the iodine toxicity, Define about the Iodine Toxicity? A w...

Define about the Iodine Toxicity? A wide range of iodine intakes is tolerated by most individuals, owing to the ability of the thyroid to regulate total body iodine. This toler

What is the nitrogen waste in amphibian larvae, Q. What is the nitrogen was...

Q. What is the nitrogen waste in amphibian larvae and in the adult animal? The terrestrial adult excretes urea since amphibian larvae are aquatic they excrete ammonia.

Explain phylum arthropoda, Phylum Arthropoda : (8,00,000 to 10,00,000 spec...

Phylum Arthropoda : (8,00,000 to 10,00,000 species) They are known as 'jointed footed' animals. The appendages are paired, and jointed with chitinous exoskeleton, varied and wi

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