Bio 252: Microscopy Study THE COMPOUND MICROSCOPE

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1 Name: Date: Block: Microscope Number: Bio 252: Microscopy Study THE COMPOUND MICROSCOPE I. Introduction The compound microscope is one of the most important instruments used by biologists today. Through observation of microscopic organisms and microscopic structures, scientists have discovered many things about the world around us and how it operates. In this investigation, you will learn the basic skills necessary to use the microscope correctly. Knowing these skills will be very helpful and important to your study of Biology. Purpose: To be able to use the microscope safely, efficiently, and effectively. Objectives: Demonstrate the use of the compound microscope. Make a wet mount. II. Materials Compound light microscope Lens paper Slides, prepared and unprepared Medicine dropper Cover slips Newspaper Scissors Forceps Label the parts of the microscope, use the figure on page 1112 of your textbook as a guide: 1

2 III. Procedure A. Use and Care of the Microscope 1. Always use both hands when carrying the microscope, one hand beneath the base and the other holding the arm of the microscope. Walk with it held close to your body. Why is this important? Demonstrate proper carrying technique to your lab partner. 2. Set the microscope at least 5 centimeters from the edge of the table. Why is this important? 3. Plug in your microscope and check the position of the cord to be sure it is out of the way. 4. Begin at the top of the microscope and locate the following parts by comparing your microscope to the diagram above. 5. Locate the eyepiece at the top of the body tube. The eyepiece contains a lens. If the lens is dirty, clean it with lens paper. Never use anything other than lens paper to clean the lenses of the microscope. What would be the result of cleaning the lenses with something other than lens paper? 6. Calculating Total Magnification: eyepiece power X objective power= Total Magnification 7. The magnification written on the ocular lens (eyepiece) is:. 8. Locate the revolving nosepiece, which carries the objectives. a. What is the magnification on the scanning objective (the smallest objective): b. What is the magnification on the low power objective (the medium objective): c. What is the magnification on the high power objective (the largest objective): 9. What is the lowest TOTAL MAGNIFICATION when using this zoom lens? 10. What is the highest TOTAL MAGNIFICATION when using this zoom lens? _ 11. Turn on the light so that light is reflected through the hole in the center of the stage. 12. After locating the stage, place a prepared slide of the letter e directly over the hole in the stage as you would read it. Secure the slide with the stage clips. Why is this necessary? 13. Locate the coarse adjustment knob. Turn this knob TOWARDS you until the objectives are raised as far as they can go. Using the revolving nosepiece, turn the low-power objective into position over the stage. When focusing the microscope, ALWAYS BEGIN ON LOW POWER. While observing the microscope stage from eye level, use the coarse adjustment knob to move the stage up as far as it will go. Then focus with the both the coarse and fine adjustment knobs until the object to be observed comes into view. 2

3 14. Draw and label your observation below. In what three ways is the image of the letter e different through the microscope as compared to looking at it without the microscope? While looking through the eyepiece at the letter e, move the slide to your right. How does the letter appear to move? Now move the slide to your left. How does the letter appear to move? If you were tracking a microorganism that appeared to be moving from the right side of your field of vision to your left, which way would you move the slide to keep it in view? Why? If that same organism suddenly changed direction and started to move toward the bottom of your field of vision, which way would you move the slide to keep it in view? Why? 16. Complete focusing with the fine adjustment. When the microscope is focused on low power, you may switch to high power. Before switching to high power, make sure that the object you are viewing is exactly in the middle of your field of vision. DO NOT USE THE COARSE ADJUSTMENT TO FOCUS AT HIGH POWER YOU MAY BREAK YOUR SLIDE. Focus with the fine adjustment until the image is clear. 3

4 17. Draw and label your observation. 18. How does high power change your field of view? How does high power affect the brightness of the image? 19. Locate the diaphragm. It can be found directly under the stage. Carefully change the setting while looking through the eyepiece. What is the function of the diaphragm? What does too much light do to the image? Too little light? B. Identification of Parts of the Microscope and Their Functions. 1. Complete the following table (do research in your textbook or on the Internet.) Part Eyepiece Body tube Revolving nosepiece Low-power objective High-power objective Stage Stage clips Diaphragm Coarse adjustment Fine adjustment Light Base Arm Function 4

5 Name: Date: Block: Microscope Number: CCP Biology Microscopy Study ADVANCED MICROSCOPY I. Introduction In this portion of your investigation, you will learn new, more advanced microcopy skills. II. Materials Compound light microscope Slides Medicine dropper w/ water Cover slips Thread Toothpick Elodea leaf Barnes bottle of Iodine w/ dropper III. Procedure A. Depth of Field Under the compound light microscope, most objects are observed in a drop of water. If you think of that drop of water as a pond and the microorganisms as fish in the pond, you will begin to see why it is important to be able to focus at different depths. Depth-of-field focusing is always done under high power and with the fine adjustment knob. 1. Obtain a prepared slide of threads. 2. Find the place where the threads cross under low power and bring them into focus. Adjust the slide so that the point at which they cross is exactly in the center of your field of vision. Can you see all 3 threads at the same time? 3. Switch to high power and observe the point at which the threads cross. Can you see all 3 threads in focus at the same time? 4. Slowly turn the fine adjustment up and down until you have seen both of the threads in focus. Draw your observations in the space below. Label which thread is on top. Be sure, as in any drawing, to title the drawing and include the magnification of the drawing. 5

6 B. Making a Temporary Wet Mount Plant Structures 1. Clean a glass slide and coverslip with a soft cloth. Be careful to hold them by the edges to avoid smudging them with fingerprints. 2. Using forceps (tweezers) peel a leaf of Elodea from the main plant. 3. Using a medicine dropper, place one drop of water in the middle of the slide (see diagram). 4. With forceps, place the Elodea leaf in the drop of water. 5. Place the coverslip at the edge of the drop of water at a 45 angle (see diagram). Check to see that the water runs along the edge of the coverslip. Lower the cover slip slowly to prevent air bubbles from forming. There should be a continuous layer of water between the slide and the coverslip. You may need to tap the coverslip gently to eliminate air bubbles. 6. As the water evaporates from the slide, you may need to add water to keep your slide fresh. This is done by placing the tip of the dropper next to the edge of the coverslip and adding a drop of water, which will run underneath. If you added too much water, it may be removed by using the corner of a paper towel to soak up excess water. Never lift the coverslip to add or take away water. 7. Place your wet mount of the Elodea leaf on the stage of the microscope. 8. Examine your slide under the low-power objective of the microscope. Draw what you see both in low power and in high power. Be sure to label any structures that you might recognize. 6

7 C. Animal Cell Structures 1. Using the toothpick, rub the inside of your cheek for 30 seconds. 2. Place a drop of water on the slide and stir the toothpick in the water for 10 seconds. 3. At a 45 angle drop a coverslip on to the specimen. 4. Use a dropper pipette to place a drop of iodine solution at one end of the coverslip. 5. Hold a piece of paper towel near the opposite edge of the coverslip. This will draw the iodine under the coverslip, where it will stain the cheek cells. 6. Examine your slide under the low-power objective of the microscope. Draw what you see both in low power and in high power. Be sure to label any structures that you might recognize. Clean-up: Dry the microscope stage completely when you have finished. Be certain that you remove specimens/slides from the stage. Place the scanning objective over the opening in the stage. Lower the stage to its lowest position. Wrap the cord, correctly, around the eyepiece and coarse adjustments and replace the dust cover (if you have one). Return your microscope to your correct storage area. Dry your work station and return all materials to the proper place as directed by your teacher. 7