Yours

3.2: Light Microscopy Procedure

HGTC BIO 225: Microbiology Lab Manual · LibreTexts

0%

Contents

    Text

    Size
    100%
    Theme
    Typeface
    Line length
    Spacing

    From LibreTexts, under CC BY 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

    Light Microscopy Procedure

     

    Name: _____________________________________________________ 

    Course Section: ______________________________________________

     

    The following activity will teach students how to use a compound light microscope and oil immersion lens. Read the following procedure carefully before starting the activity

     

    Materials
    • 5 Pre-Made Microsocpe Slides
      • 1 Gram Positive Bacterial Species
      • 1 Gram Negative Bacterial Species
      • 1 Pathogen of Your Choice
      • 1 Fungi 
      • 1 Protozoan 
    • Compound Light Microscopes
    • Lens Paper, Lens Cleaner, and Lens Oil 

     

     

    Procedure 

     

    Step 1: Get into groups of 2 and decide which five slides you will work with. Make sure you select one slide of each type specified in the materials column. Collect the remaining materials listed. 

     

    Step 2: Microscopes should be set with the stage down and on the lowest dry objective, 4x, before you begin. Make sure your microscope is plugged in and the light turned on. 

     

    Step 3: Place one slide on the microscope stage in between the stage clips. Use the course knob to move the slide up towards the 4x dry objective until the specimen is focused. 

     

    Step 4: Switch to the 10x dry objective and use the fine knob to re-focus the image.

     

    Step 5: Switch to the 40x dry objective and use the fine knob to re-focus the image. 

    • During Steps 3 to 5, you may want to decrease or increase light exposure using the bright adjustment, diaphragm, or condenser. This will assist you in focusing the specimen.
     
    Procedure 

    Step 6: When the specimen is focused on the 40x objective. Slightly move the nose piece so that the 40x dry objective and 100x oil immersion objective straddle the slide. At this point, an objective lens should not be near or touching the slide, they should be located on each of the slide.

     

    Step 7: Add a small amount of immersion oil onto your slide then gently move the 100x oil immersion objective onto your specimen. You may need to use the fine knob to fix focus slightly. Record your observations below.

    • NEVER put oil on the 40x objective. If you "lose" your specimen image when you switch to the 100x oil objective you will have to clean off your slide and lens (as described in Step 8) and start over with the 4x dry objective (Step 3). 
    • This means, once oil is on your slide you CAN NOT switch back and forth between the 40x and 100x objectives. This will damage the 40x objective. 

     

    Step 8: When you are done viewing your specimen, you must clean your microscope. First, spray lens cleaner onto lens paper. NEVER spray cleaner directly on the microscope, this will damage it.

    • Gently, swipe the lens paper across the 100x objective lens in a back and forth manner. 
    • Dry lens paper may be used to wipe down the dry objective lenses and light source. 
    • Switch back to the 4x objective and use the coarse knob to lower the stage all the way down.
    • Cover the microscope with its protective plastic, place it back in the microscope cabinet, and close the cabinet doors.
     

    Observation Results 

    Observe your five microscope slides under oil immersion. Write the name of the specimen you selected, illustrate the magnified image, and record your total magnification. 

     

    clipboard_e6a1c53c73ed7c46038c916c5fee7fabf.png

    clipboard_e74338ed3b22cb9d62186e4886c609050.png

    clipboard_ed2178059b96d45cff40227815e5a1adc.png

     

    Observation Results 

    Observe your 5 microscope slides under oil immersion. Write the name of the specimen you selected, illustrate the magnified image, and record your total magnification. 

     

    clipboard_e197a78afe580861d42a69550f9526bcb.png

     

    clipboard_e698a6c8bb4594c8bb770c5cbffe893e8.png

     

    Label The Parts of the Microscope

    clipboard_e6231af464ba9db246defbc6c7b939678.png

     

    Figure 1. Label the 9 parts of the microscope. 

     

    General Questions  

    1. Do all microbes have the same structure? Explain your reasoning.

     

     

     

     

    2. What is the purpose of using immersion oil?

     

     

     

     

    3. What is the function of the:

    A) Ocular Lens:

     

     

    B) Coarse and Fine Knob:

     

     

    C) Nosepiece:

     

     

    D) Diaphragm:

     

     

    4. How can resolution and contrast be increased?

     

     

     

     

    5. A microscope has 10x power ocular lens and a 60x objective lens. What is the total magnification power of this microscope? 

     

     

    6. What microbial agent causes malaria?

     

     

     

     

     

    7. What are the advantages of using a microscope to determine if a patient has malaria?

     

     

     

     

     

    8. How do we use a microscope to determine if the Plasmodium parasite is present in a blood sample? 

     

    Attributions

    "Microbiology Laboratory Manual: Labs, 1.4 Microscopy" by Dr. Rosanna Hartline, LibreTexts: Biology, West Hills College Lemoore is licensed under CC BY-NC-SA 4.0

    "Microbiology Laboratory Manual: Labs, 1.5 Get to Know the Microscope and Microbes" by Dr. Rosanna Hartline, LibreTexts: Biology, West Hills College Lemoore is licensed under CC BY-NC-SA 4.0

    Image Citations 

    Figure 1. "Part of a microscope" by Sue Waters on Creative Commons is licensed under CC BY-SA 2.0

    3.2: Light Microscopy Procedure is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by LibreTexts.