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Group 5

Page history last edited by PBworks 17 years, 7 months ago

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How Microscopes Work · Pros and Cons · Images · Sources

(hover for description)

(by Julia and Jessica)

Compound Light Microscope

The Compound microscope is made up of two or more double convex lenses. The lower lens (which is closer to the object), is called the objective, and the upper lens (which is closer to the eye of the observer), is called the eyepiece. The typical microscope is capable of increasing the object by 1000 times.

Sample Preparation: None is needed.

Scanning Electron Microscope

Electron Microscopes are instruments that use beams of electrons to examine objects on a very fine scale. By using these microscopes you can find the following:

Topography: surface of an object. Example: texture, hardness.

Morphology: the shape and size of the particles making up the object. Example: strength, reactivity.

Composition: The Elements and compounds that the object is made up of. Example: melting point, reactivity, and hardness.

Sample Preparation: Deposit a metal film onto the specimen's surface.

Transmission Electron Microscope

Transmission Electrons use a beam of highly focused electons that are directed toward your subject. These energetic electrons interact with the atoms of the subject, producing radiation and particles. These particles provide information about the subjects characteristics.

Sample Preparation: The sample has to be as thin as 100 nm.

(top)

Pros and Cons (by Jeena)
	Compound Light Microscope	Scanning Electron Microscope	Transmission Electron Microscope
+	has two systems of lenses for greater magnification (eyepiece lens and objective lens)	has a large depth of field – allows much more of a specimen to be in focus at one time	can magnify objects up to 1,000,000 times
+	eyepiece has achromatic doublet lens;appears to have a bigger hole to look through, so easier to use	produces images of greater resolution	great depth of field ensures that the images are very sharp
-	cannot magnify more than 2000X	cannot produce color	cannot view living specimens because this microscope involves high-energy particles
-	cannot view viruses, molecules, and atoms	as the resolution increases, the field of view decreases - becomes very difficult to view the molecular detail within the cell	image brightness is low