MICROSCOPE LAB: OBSERVATIONS AND ANALYSIS

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1 A compound microscope is an expensive precision instrument that requires special care and handling. In this activity, you will learn the parts of a compound microscope, the function of each part, and the proper care and use of the microscope. I. Parts, Care and Function of the Microscope 1. Carrying the microscope 1. Always carry the microscope with both hands. Grasp the arm of the microscope with one hand and place your other hand under the base. 2. (Your instructor will demonstrate the proper way to transport a microscope.) 3. Always hold the microscope in an upright position (so the eyepiece will not fall out.) 4. Place the microscope at least 10 cm from the edge, with the arm facing you. 2. Microscope Parts - Read and make sure you understand the function of each part of the microscope. a) BODY TUBE- long tube that holds the ocular lens b) REVOLVING NOSEPIECE - This part holds the objective lenses and is able to rotate to change magnification c) OBJECTIVE 4X: scanning objective lens with a total magnification of 40X d) OBJECTIVE 10X: Low power objective lens with a total magnification of 100X e) OBJECTIVE 40X objective lens with a total magnification of 400X f) STAGE CLIPS - These are used to hold a slide in place on the stage g) DIAPHRAGM - This part of the microscope helps you adjust the amount of light that reaches the specimen h) LIGHT SOURCE - Projects light upwards through the diaphragm to allow you to see the specimen. i) OCULAR LENS- The 10X lens you look through on a compound microscope j) ARM - This part on the side of the microscope is used to support it when it is carried. k) STAGE - Part of the microscope that supports the slide that is being viewed l) COARSE ADJUSTMENT KNOB - This part moves the stage up and down to help you get the specimen into view m) FINE ADJUSTMENT KNOB - This part moves the stage slightly to help you sharpen or fine tune your view of the specimen. n) BASE - The bottom part of the microscope. 3. Calculating the Magnification 1. Observe the numbers etched on the objectives (Example: 4X) and on the ocular (10X). The TOTAL magnification is found by multiplying the magnification of the objective by the magnification of the ocular. 2. EXAMPLE: If the magnification of the object was 20X and the ocular was 10X, the total magnification would be 20 X 10 = 200 X. In other words, the specimen seen through the microscope would be 200 times larger the viewed with the naked eye. 3. Complete the data table on your answer sheet to find the total magnifications of each objective on our microscopes. 4. Cleaning the lenses 1. Lens Paper should be used to clean any of the lenses of the microscope. Lens paper is provided to you by your instructor. Never use anything other than lens paper to clean the lens on the microscope, including your fingers. 5. Illumination 1. After you plug the microscope in and turn on the illuminator, rotate the Iris diaphragm on the underside of the stage in order to adjust the light intensity. Look through the microscope as you adjust the diaphragm and observe the changes. Set the diaphragm and move on. 2. Keeping the light intensity in mind, look through the microscope and move through the different magnifications slowly. Observe the change in light intensity. 3. Adjust the intensity of light to match the requirements of the objective you are wishing to view.

2 6. Focusing on low power 1. Place the slide on the microscope stage, with the specimen directly over the center of the glass circle on the stage (directly over the light). NOTE: If you wear glasses, take them off; if you see only your eyelashes, move closer. Be sure to close, or cover your other eye!! 2. Twist the knob away from you to lower and towards you to raise. 3. If, and ONLY if, you are on scanning objective lens, lower the objective lens to the lowest point, then focus using first the coarse knob, then the fine focus knob. The specimen will be in focus when the Scanning objective lens is close to the lowest point, so start at the lowest point. 4. Focus by slowly raising the lens. If you can t get it at all into focus using the coarse knob, then switch to the fine focus knob. 5. Adjust the Diaphragm as you look through the Eyepiece, and you will see that MORE detail is visible when you allow in LESS light! Too much light will give the specimen a washed-out appearance. 6. Once you have found the specimen on Low Power (4x) center the specimen in your field of view, then, without changing the focus knobs, switch it to Medium Power (10x lens). If you don t center the specimen you will lose it when you switch to Medium. 7. Once you have it on Low Power remember that you only use the fine focus knob! 8. Repeat steps 6 and 7 to change to High power (40x) 9. CAUTION! -- Caution, use only the fine focus knob. Caution, do not remove the slide when it is on High Power. -- The High Power Objective (430x) is very close to the slide. Use of the coarse focus knob will scratch the lens, and crack the slide. **** NEVER use the coarse adjustment when focusing on the medium and high power objectives!!!!! II. Tips for making good sketches 1. All drawings must be in color! But, Use a regular pencil to sketch, then color in with colored pencils. 2. Don t even think of starting your drawing unless you have a PENCIL! Drawings in PEN are UNACCEPTABLE! This is for two reasons: (a) You can erase pencil! (b) You can shade in areas more easily in pencil. Once you have drawn in pencil, use color pencils to add color and detail. 3. Draw a large circle the represents EVERYTHING you see on the slide. Use a roll of masking tape to draw circle. 4. Each Drawing must be minimum 1/4 page in size, and must include clear, proper labels! In the upper left hand corner of each circle include the specimen name as written on the slide label. In the upper right hand corner, include the magnification (look at lens). 5. Labels should start on the outside of the circle. The circle indicates the field of view as seen through the eyepiece. All arrows should end with the point touching the object to be labeled!

3 II. Preparing a wet mount slide & Magnification 1. Wet mount slide - Now that you have learned how to use a compound microscope it is time to learn how to prepare a wet mount slide. 1. Using a pair of scissors cut a small letter e from a piece of newspaper. Cut the smallest letter e you can find. Position the letter e on the center of a clean microscope slide. 2. Using a dropper, place a drop of water on the piece of newspaper. 3. Hold a clean cover slip in a vertical position (90 degree angle) next to the water. Make sure the bottom edge of the cover slip is in the drop of water on ones side. Lower the cover slip rolling it down, to avoid trapping air bubbles between the cover slip and the slide. 4. Make sure the bottom of the slide is dry before you place it on the stage of your microscope. 2. Viewing objects with the Microscope 1. Center the wet-mount of the letter e on the stage with the e in its normal upright position. Bring the letter in to focus under low power using the procedures you learned in number 6 above. 2. Note the position of the letter e on the slide (using your eyes only) and as seen through the eyepiece of the microscope. 3. Draw the letter e as seen through the microscope on the observation sheet. Be sure to record the magnification. 4. While looking through the microscope, move the slide to the left, notice which way the letter e moved. Now move the slide to the right. Notice which way the letter e moved. Do the same with moving the slide away and towards you. 5. Turn the medium power objective into position and bring the letter e into focus using what you learned in number 7 above. Draw the letter as seen through the microscope on your observation sheet (letter B). Don t forget to record the total magnification. 6. Looking at the side, rotate the high power objective into position. Bring it into focus using the fine adjustment knob ONLY. (if you lose the object, start again from number 6 above) Draw the letter e as it appears in the microscope on your observation sheet (letter C) and record the magnification. 7. Remove the slide and clean of the letter e You will use this slide again in the next step. 3. Resolution (applies to question 19) 1. Cut a small piece of a colored picture from a magazine (red, blue, yellow, orange, etc). 2. Prepare a wet mount slide of the colored object using the slide from the previous section. 3. Bring the colored picture into focus under low power, then medium power, then high power. 4. Compare the appearance of the photograph (piece of color picture from a magazine) you observe with the naked eye to the way it appeared when you observed it using the microscope. Relate this observation to the concept of improved resolution. (the ability to pull out tiny details). 5. Using high power, make a colored drawing of your object on the observation sheet (letter D). Remember to include magnification and specimen. 4. Explore: Repeat all of the above with two additional slides

4 Answer the following questions as you read through the Compound Microscope lab Parts, Care and Function of the Microscope 1. What are the three rules to carrying a microscope? a. b. c. Microscope Part Relationships 2. How is the arm and base related? 3. How are the body tube and the ocular lens related? 4. How are the stage and stage clips related? 5. How is the revolving nosepiece and the objective lens related? 6. How is the light source and diaphragm related? 7. How are the fine and coarse adjustments related? 8. How is the ocular lens and the objective lenses related? Calculating the Magnification 9. What is the total magnification power of your microscope under the following operating conditions? OBJECTIVE OCULAR TOTAL MAGNIFICATION (X) 4x 10x 10x 10x 40x 10x Cleaning the lenses 10. If your microscope lens is dirty what should you use to clean it? Illumination 11. What happens to the light intensity as you adjust the diaphragm? Explain your answer. 12. In what position should the stage be located when you first begin to focus in on an object? Why would you put it in this position? 13. What happens to the SIZE of the field of view of a microscope when you switch from low power to high power? (Does the field of view the amount of the object you can see become larger of smaller?

5 14. Explain why it is important not to use the coarse adjustment knob when on the high power objective? Preparing a wet mount slide & Magnification 15. When preparing a wet mount slide why do you make sure you are rolling the cover slip down? 16. Compare the POSITION of the letter e as seen with the microscope to the POSITION of the letter e on the slide, how has it changed? If it is right side up and forward on the slide, how is it seen through the microscope? 17. When you move the slide to the left on the stage, in what direction does the image appear to move? 18. How does the colored paper look different under high power?

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