1 Intro to Microscopy.pdf - E X E R C I S E Introduction to...

This preview shows page 1 - 3 out of 11 pages.

Objectives:Throughout this course, you will be using the compound light microscope to exam-ine bacteria and other microorganisms. The following exercise is designed to explain how a micro-scope works and to teach the proper use and care of the microscope. Upon completion of thisexercise, you should be able to do the following:Identify the major parts of the microscope and know the function of each.Know which objective lens to use when viewing eukaryotic specimens.Know which objective lens to use when viewing prokaryotic (bacteria) specimens.Define and calculate magnification.Define resolution.Know when and why immersion oil is used in microscopy.Know how to properly use, clean, and store the microscope.Applications:In the clinical setting, light microscopy is the most common method used forimmediately detecting microorganisms in patient specimens and for characterizing microbesgrown in culture. One of the most important and basic techniques required in microbiology is the effective use ofthe microscope. A typical microscope can magnify images approximately 1000X. This allowsobservation of the size, shape, and motility of prokaryotic cells. In light microscopy, light is transmitted through a specimen and then passes through a series ofmagnifying lenses. The compound microscope has two sets of lenses: the ocular, and the objec-tive. Your microscope has 4 objective lenses:Objective Lenses of the Compound Light Microscope:4X: scanning lens10X: low power lens; useful for initial searching & focusing40X: high dry lens; used to view most eukaryotic cells100X: oil immersion lens; used to view bacterial specimensThe ocular lens has a magnification of 10X. The total magnification is equal to the objective mag-nification multiplied by the ocular magnification. Therefore:Total Magnification:Scanning: (4X)(10X) = 40XLow power: (10X)(10X) = 100XHigh Dry: (40X)(10X) = 400XOil Immersion: (100X)(10X) =1000X1EXERCISEIntroduction to MicroscopyKD07-001.pdfFrom Fundamentals of Microbiology for Allied Health by Kathleen Dannelly, Angela K. Chamberlain, and William M. Chamberlain. Copyright © 2009 by Kendall Hunt Publishing Company. Used with permission.
Two characteristics, the resolution and the magnification, determine the performance of a micro-scope. The usefulness of a microscope depends not so much on the degree of magnification, as onthe ability to clearly separate (resolve) two objects that are close together. Resolution is a measureof the clarity and detail of a magnified image and is measured as the shortest distance between twoadjacent points that appear distinct, not as a single blur. Magnification produces an image thatappears larger and is measured as the ratio of image size, as seen through the microscope, to theactual size of the object. Magnification without detail is useless; two points that appear as a blurat low magnification will remain a blur at higher magnification. The best light microscope has amaximum resolution of 0.2 μm and a practical magnification of 1000X—a resolving power

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture