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1 Lab: Cells and the Microscope Purposes: To familiarize ourselves with the microscope parts. To examine cells in a microscope and identify cell parts. To learn how to use a microscope properly. To learn the proper mathematical procedures for calculating magnification, field of view size (FOV) and the size of objects in the FOV. Materials and Apparatus Microscope with light source Slide with ruler on it Prepared slide of Spirogyra Procedure: Identifying Microscope Parts 1. Examine the diagram below and identify all the parts on your microscope. 2 Calculating Magnification 1. Examine the objective lenses and find the numbers written on each lens. 2. Find the number on each lens that is written with the largest font size. 3. Record these numbers in the chart below. These are the magnifications of each objective lens. Lens Magnification Low (black) Medium (yellow stripe) High (blue strip) Ocular / Eyepiece 4. Examine the ocular lens. Find its magnification and record it in the chart above. 5. The total magnification for each of the objective lenses is calculated using the following formula. Total Magnification = ocular magnification x objective magnification 6. Use the formula above to calculate the total magnification for each of the objective lenses. Record your mathematical steps and answers in the following chart. Lens Calculation Steps Answer Low Medium High Calculating Field of View 7. Turn on your microscope. 8. Turn the nosepiece of your microscope until the low power objective lens is above the light that is coming through the stage. 9. Place a ruler slide onto the stage and clip it into position. 10. Use the stage control knobs to position the ruler over the light and under the low power lens. 11. Look through the eyepiece and find the lines of the ruler. You may have to re-position the slide ruler so that it is visible in the eyepiece. You can do this by using the stage control knobs while you look into the eyepiece. 12. When you can see the ruler use the coarse adjustment knob to focus what you see. 13. Look into the eyepiece and measure, using the slide ruler, the distance from one side of the FOV circle to the other. Record the FOV diameter below. FOV diameter @ low = ______________ mm 3 14. Calculate the FOV diameter at medium using the following formula. Substitute and solve. FOV diameter @ med = FOV @ low x mag @ low mag @ med 15. Calculate the FOV diameter at high using the following formula. Substitute and solve. FOV diameter @ high = FOV @ low x mag @ low mag @ high Examining Spirogyra 16. Make sure your microscope is on and the nosepiece is turned to the low power lens. 17. Place a slide of the Spirogyra onto the stage so that the colored circle of the slide matches up with the circle of light coming through the stage. Use the stage control knobs to help you position the slide appropriately. 4 18. Look into the eyepiece. Adjust the microscope with the coarse adjustment knob until you can see green strands in the eyepiece clearly. These green strands are the green algae Spirogyra. It lives mostly in fresh water ponds. 19. Use the stage control knobs to center a group of the Spirogrya strands in your FOV. 20. Rotate the nosepiece so that medium (yellow stripe) lens is above the slide. 21. Use the fine adjustment knob to observe the green strands clearly as you look through the eyepiece. You may have to use the stage control knobs to re-position the strands so they are again centered in the FOV. 22. Once you have focused at medium power switch to high power (blue stripe). Rotate the nosepiece so the high power lens is above the slide. 23. You may have to use the stage control knobs to re-position the strands so they are again centered in the FOV. 24. Again, use the fine adjustment knob only to focus on the specimen. Choose one of the Spirogyra strands to focus on. 25. Look through the eyepiece and slowly rotate the fine adjustment knob back and forth. This will enable you to look at the specimen at different depths. 26. Draw a detailed di

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