Petrographic Microscope Parts And Functions Pdf

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The polarized light microscope is designed to observe and photograph specimens that are visible primarily due to their optically anisotropic character.

One of the wonders of the scientific world is that so much of what goes on is invisible to the naked eye. Invented in by a Dutch optician named Zacharias Janssen, the compound or light microscope gives students and scientists a close-up view of tiny structures like cells and bacteria. Read on to find out more about microscope parts and how to use them. The eyepiece contains the ocular lens, which the user looks through to see the magnified specimen. The ocular lens has a magnification that can range from 5x to 30x, but 10x or 15x is the most common setting.

2.4 Parts of the Petrographic Microscope

In this section, we explore the parts of the petrographic or polarizing light microscope. This section is appropriate for students who have no prior experience with using microscopes. What does a microscope look like? Although all petrographic microscopes have common parts and functions, there are many brands of microscope, each of which may look different. If petrographic microscopes are maintained and handled carefully, they can last for literally generations of students. The microscopes in your classroom or the laboratory could be new, a few years old, or decades old, and have different design aspects from younger or older microscopes.

The petrographic, or polarizing, microscope, a compound instrument using plane-polarized transmitted light, has been applied for over a hundred years as a standard tool in the examination of rock textures and optical properties of minerals. Microscopes using reflected light are also available for the examination of opaque minerals. Polarization of light in modern microscopes is achieved by a synthetic material made of a plastic film containing a mass of fine-grained prismatic crystals of herapathite a complex sulfate and iodide of quinine with a parallel orientation. Early instruments used nicol prisms made of two elements of calcite cleavage rhombs cemented together in a particular optical orientation by balsam to achieve the same effect. Skip to main content Skip to table of contents. This service is more advanced with JavaScript available. Petrology Edition.

This section provides an overview of the parts of a petrographic microscope and what each part does. It is also a good review for a student who has used a petrographic microscope in a previous class but needs a refresher on the anatomy of a microscope. Look at the diagrams of the petrographic microscope and its parts in Figures 4. List all that you feel you completely understand how to use here:. In how many places is the thin section image magnified in a petrographic microscope? How do you determine the magnification of the image? Descriptions of the microscope parts, from top to bottom, are found in the list below or in these references:.

Petrographic Microscope Parts And Functions Pdf

Previous Table of Contents Next. A petrographic microscope, also called a polarizing microscope , is best described as a compound, transmitted-light microscope to which components have been added to enable the determination of the optical properties of translucent substances. The designation of the microscope as a compound microscope indicates that it has an ocular that focuses on a virtual image of the subject produced in the tube of the microscope by the objective lens. The professional petrographic microscope has a substage condenser that can be centered and focused. The substage has field and aperture diaphragms. The polarizing components are the upper and lower polarizing devices, the Bertrand lens and its mounting between the upper polarizing device and the ocular , an accessory flip-in lens for convergent light mounted as the top element of the condenser, and a graduated rotating stage with a removable click stop that can be activated to indicate a degree rotation from any selected direction. The focus knob s and the stand are graduated to permit the determination of thickness by differential focusing.

This type of microscope differs from the normal one by using a polarized light, in which the light waves vibrate in one direction. Unlike the ones from normal light that vibrate in random directions. When studying a specimen the light has to pass through a polarizer polarizing filter and then in some cases through an analyzer — to increase the quality of image contrast. A polarizing microscope can be obtain from a compound or a normal one by adding some pieces. The mainly differences between a polarizing microscope and other microscopes:. A polarizer is a filter that only allows specific light waves or vibrations to pass through it and focus them in a single plane. An analyzer, mainly used as a second polarizer located above the sample, determines the quantity and the direction of the light that illuminates a sample.

Relatively few of us are lucky enough to have and use a wide range of makes and models of microscopes. Work-place microscope labs often have little variety in brands or models, so as to reduce costs for maintenance and accessories. But because I have moved around a few times since the early s, different microscopes have been available for my geological field research and education. An enjoyable if challenging task in the s was teaching optical mineralogy and petrography with polarizing microscopes pol scopes , in advanced undergraduate courses in academic geology programs. In recent years, I have been servicing, refurbishing, and selling microscopes in a part-time business. There is nothing mysterious or strange about the polarized light accessories used in a petrographic geological microscope. Its brightfield capabilities continue as in any good biological microscope, with the addition of polarizing filters placed above and below the sample, at least one of which can be easily moved in and out of the light path.

Polarizing microscopy

Polarized light is a contrast-enhancing technique that improves the quality of the image obtained with birefringent materials when compared to other techniques such as darkfield and brightfield illumination, differential interference contrast, phase contrast, Hoffman modulation contrast, and fluorescence. Polarized light microscopes have a high degree of sensitivity and can be utilized for both quantitative and qualitative studies targeted at a wide range of anisotropic specimens. Qualitative polarizing microscopy is very popular in practice, with numerous volumes dedicated to the subject. In contrast, the quantitative aspects of polarized light microscopy, which is primarily employed in crystallography, represent a far more difficult subject that is usually restricted to geologists, mineralogists, and chemists. However, steady advances made over the past few years have enabled biologists to study the birefringent character of many anisotropic sub-cellular assemblies.

A petrographic microscope is a type of optical microscope used in petrology and optical mineralogy to identify rocks and minerals in thin sections.

Parts of the Microscope and Their Uses

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Key Terms. Eyepiece. Viewing tube. Bertrand lens. Analyzer. Accessory plate. Revolving nosepiece. Objective. Rotating stage with goniometer.


Microscopy U - The source for microscopy education

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Petrographic Microscope Parts And Functions Pdf

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