Biological Microscope Components

Biological Microscope Components - Biological Microscope...

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Unformatted text preview: Biological Microscope Components Biological microscopes are specially desgined to view primarily fluid-like speci- mens that are held between a microscope slide (on the bottom) and a thin cover glass (on the top). The cover glass is usually 0.17 mm or 0.18 mm thick. The specimen is il- luminated from below so that the light propagates through the microscope slide, then through the specimen, and then through the cover glass. Due to the large angles of the rays with respect to the axis of the optical system, the cover glass slab introduces spheri- cal aberration into the imaging process. To compensate for this, biological objectives are designed and fabricated that largely cancel this cover—glass—induced aberration. A biological microscope has an objective with engraved markings on it as follows: “Achro” and “40 / 0.65” and “160 / 0.17.” “Achro” indicates that it is an achromatic (color corrected) objective. The “40” means that it is a 40X linear magnification ob- jective. The “0.65” is the numerical aperture of the objective. The “160” refers to the length in mm of the microscope tube with which it is designed to be used and the “0.17” indicates the thickness in mm of the cover glass for which the objective is corrected. This microscope has an eyepice with engraved markings on it as follows: “WF10X.” The “WF” means that it is a Wide Field type of design and the “10X” is the angular mag- nification of the eyepiece. The field stop in the eyepiece is 10.35 mm in diameter. The outside of the eyepiece tube is a standard 23.2mm diameter. Calculate, showing all work, the focal length of the objective. Express your an- swer in mm accurately to three significant figures. Calculate, showing all work, the focal length of the eyepiece. Express your answer in mm accurately to three significant fig- ures. Calculate, showing all work, the diameter of the magnified area that is seen when viewing through the microscope. Express your answer in um accurately to three signifi- cant figures. Put your answers in the spaces provided below. Focal length of objective = mm Focal length of eyepiece = mm Diameter of area seen through the microscope = pm Biological Microscope Components Mk L_*' From similar triangles Then the linear magnification of the objective is I L m=— —=40.0 0 _ f0 Since L = 160 mm, then f0 = 4.0 mm. The eyepiece adjusted for infinity focus has anglular magnification M = 250mm = 10.0 fe and so f6 2 25mm The field stop has d = 10.35 mm and it located at the image plance of the objective. The diameter of the field viewed is D = i = 258.8,um m ...
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This note was uploaded on 04/29/2008 for the course ECE 4500 taught by Professor Gaylord during the Spring '08 term at Georgia Institute of Technology.

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Biological Microscope Components - Biological Microscope...

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