Microscopy Laboratory

Advanced Biology

 

 

 

Introduction – The microscope is a basic instrument used in the Advanced Biology classroom for the study of organisms in all three Domains of Life.  It enhances aspects of structure and provides the details of structure for organisms from bacteria to human cells.  All microscopes have lenses made of special glass that enable light rays emanating from a specimen to be focused and magnified for viewing( magnification).  Lenses are also able to resolve two adjacent points as separate images (resolution).  This aspect of lenses adds the ability to produce detail and clarity in an image.  The light passing through the lenses can be manipulated in a variety of ways to provide contrast between the background and the specimen (contrast).

                      The compound light microscope has two lenses, an ocular or eyepiece and an objective lens.  The magnification of the ocular is 10x.  There are four magnification of the objective lenses, 4x( scanning), 10x(low), 40X(high), and 100x( oil).  The total magnification of these lenses is the product of the ocular x the objective lens. To focus an image clearly for your eyes, you can use the coarse adjustment and fine adjustment knobs on the side of your microscope.  These move the stage up and down until a proper focus is achieved on the retina of your eye. The lenses are also parfocal.  When a focus is obtained with the scanning lens, the revolving nosepiece of the microscope can be turned so that the low power objective lens is in place and the focus should be retained.

                        Light is essential for viewing your specimen.  There are two methods available for adjusting the light.  The first method is to locate the iris diaphragm underneath the stage of the microscope.  This works like the iris of your eye that opens and closes your pupil.  The iris diaphragm can be used to manipulate the amount of light passing through the specimen.  Light may also be adjusted by raising or lowering the condenser lens.  The condenser collects and directs light passing through the specimen.  Not all microscopes have a condenser lens adjustment.  It is important to adjust the condenser to the position that enhances the clarity of the image.

                       

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Microscope Links

http://www.cas.muohio.edu/~mbi-ws/microscopes/compoundscope.html

http://www.microimaging.ca/microscope%20parts.htm

 

 

Materials –

 

Comic strip from the newspaper

Three threads of different colors

Salt crystal

Slide

Lens paper

Diagram of the microscope

Worksheet

 

Procedure –

 

  1. Identify the parts of the microscope using your reference sheets.
  2. Label your diagram
  3. Before beginning the lab exercise, clean all of your lenses with lens paper.
  4. Always clean the slides that you get from the supply tabl

 

 

Exercise I- Learning to focus.

  1. Obtain a slide, coverslip, and a small piece of comic strip paper from the supply area.
  2. Place the comic strip paper on the slide and weigh down with a coverslip.
  3. Place the slide on the stage.  If your microscope has a mechanical stage, make sure that the slide is in the clips.  Make sure that the slide is flat for viewing.
  4. Center the comic strip picture on the slide so that you can see that light from the condenser is passing through it.
  5. Turn the revolving nosepiece of the microscope so that the scanning lens( red) is in place.
  6. Use the coarse adjustment knob on the side of your microscope to focus the image on scanning. ( Draw on your data sheet).  Repeat this process with both low power( yellow).  When you have finished your low power work.  Turn the revolving nosepiece slowly to high power( blue).  Use only fine adjustment with the high power lens.  Focus the image clearly and draw on your data sheet.
  7. What observations can you make about the amount of the object that you can see? The area that you can visualize on the slide is referred to as the size of field. How does this change from scanning to high power?

 

 

 

 

 

 

 

Exercise II.  Contrast

  1. Place a salt crystal on a clean slide.  Place a coverslip on top of the crystal.  Focus on scanning.  Change to low power and focus again for perfect clarity.
  2. Close the iris diaphragm and draw the crystal.  Open the iris diaphragm slightly and draw the crystal.  What is the difference in contrast between the two?  A salt crystal is white.  How does the position of the iris affect the contrast and your view of the image?

 

Exercise III. Depth of Field

 

  1. Obtain three threads from the prep area in the front of the room.
  2. Place these threads on top of each other so they cross in the middle

 

           and  weigh down with a coverslip

  1. Draw on scanning, low, and high power.
  2. Can you see al the three threads at focus simultaneously on scanning?  Low? High?  What happens as the magnification increases to your ability to see a clear image?
  3. Can you tell which thread is on the top?

 

 

 

 

 

 

IV. Oil Immersion.

 

  1. Obtain a prepared slide from the supply area. 
  2. Starting with scanning repeat the focus procedure until you get to high
  3. Do not draw.
  4. Rotate the nosepiece so that the light path is midway between the high-dry and the oil-immersion objectives.
  5. Place a small drop of immersion oil onto the coverslip using the circle of light below the specimen as a reference.
  6. Rotate the oil immersion objective lens( white) until it is in the oil.
  7. Use only fine adjustment to focus the image.
  8. Adjust the lighting with your iris diaphragm.
  9. Draw your picture.
  10. Remove the slide from the oil and wipe the oil from the coverslip with lens paper.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

NAME-

Microscopy Data Sheet

I. Focus

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

Part Two. Contrast

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

Part Three. Depth of Field

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

PART FOUR. OIL IMMERSION