ELECTRON MICROSCOPE
Introduction
— At times it becomes necessary in metallurgical research to examine metal structures at very high magnifications.
— Unfortunately the highest magnification possible with an ordinary optical metallurgical microscope (Fig. 42.1) is in the region of X2000.
— For very high-power microscopy (i.e., between X2000 and X200,000) light rays are replaced by a beam of electrons and this way developed an electron microscope.
Principle
(i) Preparation of metal/alloy specimen. Most electron microscopy is carried out by using transmission-type instruments that produce images of either transparent replicas of the etched specimen or of very thin metal films obtained by various techniques. It is necessary for electron microscope specimen to be transparent to the electron beam.
Replicas are produced in plastic or some other suitable material, which reproduces faithfully the contours of the polished and etched specimen.
Thin foilsot the metals which work as (electron microscope) specimen are of 100-2000. A° thickness and are prepared by several available methods, one of which is Ion Bombardment technique and another is Electropolishing method[1].
(ii) Construction and Operation
— An electron microscope consists of an electron gun and condenser and projector lens. Vacuum is necessary to allow passage of the electron beam.
— Electrons emitted by a hot tungsten-filament cathode are accelerated, to form a high velocity beam, by the anode.
— Depending upon the density and thickness of the replica (specimen) at each point, some of the electrons are absorbed or scattered while the remainder pass through, i.e., transmit.
— The magnetic field of the objective lens focuses and enlarges the electron beam that has passed through the replica.
— Some of the electrons in this image are brought into a second focus on a fluorescent screen by the projector lens.
[1]For detail refer to Techniques of Electron Microscopy by D. H. Kay, Blackwell Scientific Publications. 1965.
I wanted to have a sample analyzed through scanning electron microscope (SEM) but the testing center only has scanning probe microscope (SPB). Is it relatively the same? What’s the difference?
Thanks in advance!
Assuming that the resolution of an electron microscope is equal to the de Broglie wavelength of the electrons used, to what speed must the electrons be accelerated to obtain a resolution of 0.16 nm?
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I am reworking some homework, and I just can’t seem to get this question right. Can anyone help me?
I wanted to have a sample analyzed through scanning electron microscope (SEM) but the testing center only has scanning probe microscope (SPB). Is it relatively the same? What’s the difference?
Thanks in advance!
The difference between the light microscope and the electron microscope is the light microscope allows light to pass through the specimen and use two lenses to form an image. While the electron microscope uses beams of electrons rather than light to produce images.
I wanted to have a sample analyzed through scanning electron microscope (SEM) but the testing center only has scanning probe microscope (SPB). Is it relatively the same? What’s the difference?
Thanks in advance!
Would you use an electron microscope or would you use a compound light microscope. I guess that my real question is, is bacterium alive?
i feel kind of dumb because i know that bacterium is alive. Which one would you use though if you needed a detailed image of the internal structure of a bacterium?
You view a piece of living tissue on the person who you get the blood from, using a high powered electron microscope. While viewing this tissue, you got too close, and crushed many of the cells within the tissue. What is the subsequent reaction you would see?