The Microscope The Microscope ► Improvements in the microscope and development of related biological techniques made our present knowledge of cell structures and functions possible. ► The compound light microscope is the major instrument for the study of cells. It will be used in the laboratory and can provide magnification up to 500X, depending on the magnification of the ocular and the objective. ► Although some compound light microscopes can provide a magnification of 2000X, there is a limitation to the magnification, due to the resolving power of the lens. ► Therefore, the compound light microscope is primarily useful for viewing large cell organelles, such as nuclei and chloroplasts. The compound light microscope has 2 lens combinations: A. The objective lens which forms a magnified image of the specimen. B. The ocular lens or eyepiece lens, which further magnifies the image. The specimen used on the compound light microscope must be transparent. WHY? There are a number key parts of the compound light microscope and the functions of these parts are as follows: 1. Ocular lens (eyepiece): used to “look through” and generally magnifies at 10X. 2. Objective lenses: found closest to the object to be studied. It provides the rest of the magnification of the compound light microscope and generally magnifies at 4X, 10X, 40X. Magnification ► Magnification of a compound microscope is the product of the power of the objective multiplied by the power of the ocular. ► Example: objective = 40X Ocular = 10X What is the total magnification? 400X Resolving Power ► Useful magnification is limited by its resolving power. ► The resolving power is the ability to separate 2 objects close together. ► The properties of light place an upper limit on the resolving power of any light microscope. 3. Stage ►The flat surface (platform) on which the specimen or slide to be studied is placed. 4. Stage Clips ►Used to hold the specimen or slide in place. 5. Coarse Adjustment: ► The larger knob ► Used primarily to focus under low power (up to 100X) only! ► It causes large movement of focusing. ► Course adjustment must never be used when the high power objective is in position. ► If you use this under high power, you will break the slide!!!! 6. Fine Adjustment: ►The smaller knob ►Used for focusing under high power and final focusing under low power. ►It causes small movement for focusing. ►The fine adjustment knob should never be turned more than one half turn in either direction. 7. Light Source: ► Provides light ► Light must pass through the object to be studied in order for an image to be viewed in the objective lens. ► In some microscopes, a mirror is present and directs the light from a horizontal surface up through the diaphragm and the specimen. 8. Diaphragm: ►It is found under the stage. ►Controls the amount of light passing through the specimen and into the objective lens. ►Smaller openings of the diaphragm increase the resolution or the amount of detail in the image. 9. Arm ►Holds the tube and the stage ►Used to carry the instrument 10. Base: ►Supports the instrument 11. Body Tube ►Hold the lenses 12. Nosepiece: ►Rotates to change the objective lens from one power to another.
Pages to are hidden for
"Microscope - PowerPoint"Please download to view full document