Lab: The Compound Microscope Purpose: To learn the parts of the compound microscope and to learn the basic skills needed to use the microscope properly. Materials: Microscope Colored paper Cover slips Slide of letter "e" Microscope slides Scissors Before beginning this lab, please read the basic rules for using a microscope. 1. Always carry the microscope by the arm with your other hand supporting the base. 2. Keep the microscope pushed back from the edge of your table. Do not leave purses, extra books, etc., on your lab table. 3. Periodically clean the lens of your microscope. Clean only with the lens paper that is provided by your instructor. Do not use paper towels, Kleenex, or any other material that is not provided by the instructor. 4. Keep the stage dry, and always make sure the bottom of your slide is dry before putting the slide on the microscope. 5. Never use the coarse adjustment knob while using the high power objectives. 6. FOLLOW THESE STEPS VERY CAREFULLY! Always start with the 4x objective. Make sure that the 4x objective is in place before using the microscope. While using the 4x objective, focus the image using the coarse adjustment knob. Once the image is in focus, carefully swing the higher-powered 10x objective in place. Focus the image using either the coarse adjustment knob or the fine adjustment know. You are now ready to view your image using the 40x objective. Move the 40x objective into place. Focus the image using ONLY the fine adjustment knob. 7. These microscopes are parfocal. This means that the corresponding focal points on all the objectives are in the same plane. In other words, if the image is in focus with one lens, it should be in focus with the other lenses. When you change objectives, only fine adjustment should be needed. 8. Return your objective to low power before viewing another slide and before putting the microscope away. PROCEDURE: The Microscope and Letter "e" 1. Make sure the shortest objective (4x) is pointing down. Locate each of the following on your microscope. Ocular Fine Adjustment Knob Coarse Adjustment Knob Rotating Nosepiece Arm Stage Clips Diaphragm Mirror or Light Source Body tube Base Objectives 2. How many objectives does the microscope have?
3. Look for the whole numbers on the objectives. How many times does each objective magnify? 4. Which objective is closest to the stage when it is pointing straight down? 5. Look for the whole number on the ocular. How many times does the ocular magnify? 6. Put the lowest power (4x) objective in place so it is pointing straight down. Turn the microscope so that the arm is facing you. Look through the ocular until you see a clear circle of light. This is called your field of view. How many lenses does the light pass through? 7. To find the total magnification when using the 4x objective, multiply the magnification of the ocular times the magnification of the objective. What is your total magnification using the 4x objective? The 10x objective? The 40x objective? 8. Turn the coarse adjustment knob away from you. Does the stage move up or down? 9. Turn the fine adjustment knob away from you. Does the stage move up or down? 10. Obtain the prepared slide of the letter e from your instructor or prepare your own slide using the following instructions: Get a clean slide from the supply table. Cut the smallest "e" you can find from the newspaper. The best size for the "e" is found in an article in the paper. Do not use an "e" from the title of an article or from the classified section. Place the "e" on a slide and cover with a cover slip. Place the slide on the stage so that the "e" is right side up. Observe the "e" with the 4x objective. Compare the position of the "e" through the microscope with the actual position on the slide. Is the image in the same position? If not, describe its position under the microscope. 11. While looking in the ocular, slowly move the slide from right to left. Which way does the image move? 12. Move the slide away from you. Which way does the image move? 13. Making accurate sketches is very important in the study of biology. Try to make a drawing to scale in relation to the field of view. Label the drawing with three pieces of information: (1) the name of the specimen, (2) the objective being used as the drawing is made, and (3) the estimated size of the specimen. Make a sketch of the "e with the 4x objective. 14. Swing the 10x objective into place. Is the field of view larger or smaller with the higher power objective? 15. Draw the "e" as seen under the 10x objective. Try to get a good comparison of the difference in size as seen with the 4x. Be sure to label the drawing with the three things listed above. 16. Get a clear focus with the 10x objective. Very carefully swing the 40x objective into position. Do not lower the stage first! It may look as if the objective is going to hit the stage, but it will not! It should be just a fraction of an inch above the cover slip. Remember, do not use the coarse adjustment knob with the 40x objective. Use the fine adjustment knob to get a clear image. What has happened to the size of your field of view? Draw the "e" as it appears under the 40x objective and label.
17. As you changed objectives while looking at the "e", did the position of the "e" change? What happened to the field of view? What happened to the actual size of the specimen? 18. You must know how to measure the size of the specimen you are looking at under the microscope. What is the diameter of the 10x field of view in microns? 19. What is the diameter, in microns, of the 40x objective? PROCEDURE: COLORED PAPER 1. From a magazine or funny paper cut out a small piece of colored paper. Place the colored paper on a clean dry slide. Place a cover slip on top of the paper. View with the 10x objective. How does the image compare with the image you see with your naked eye? Make a sketch of the colored paper as it appears under the microscope. 2. You have just seen an example of the resolving power (resolution) of the microscope. For most people, two objects that are less than 0.1 mm apart cannot be seen as separate objects by the naked eye. The microscope permits us to detect space between objects that are much closer than this. However, it can spread the objects so far apart that the picture no longer makes sense. What is resolving power (resolution)? 3. How can magnification help us? 4. How can resolution help us? 5. How can too much resolving power be a handicap? Cleaning up the Lab: Please take care of the following items before you leave the lab. 1. Wipe the lenses of your microscope. Dry any water on the stage. Put the low power objective in place, and rack the objectives as far away from the stage as possible. Return it to the cabinet, placing your microscope in the proper slot. 2. Wash and dry your slide and return it to the box. 3. Wash and dry the coverslip if it is glass and return it to the box. Plastic coverslips should be thrown away. 4. Wipe down your table. You are your partner are completely responsible for keeping your table, and the area around you, clean and neat. Do not leave anything on the table when you leave the lab. 5. Any glassware should be placed on the front table to be washed. Please do not mix your dirty glassware with any clean glassware that has already been washed. 6. All other materials should be returned to the supply table. 7. Please do not put any solid materials into the sinks! Final Observations: 1. Why should you never use the coarse adjustment knob while using the high power objectives? 2. Why must the bottom of slide and the stage be kept dry? (Hint: It won't hurt the stage!) 3. What is a parfocal microscope? What is the advantage of this? 4. What is the total magnification using the three objectives of your microscope? 5. What is the diameter of the field of view with each objective? 6. Was it easier to estimate the diameter of the e using the 10x or 40x objective? Why? Which estimate do you think is more accurate? 7. What three things should always be given with a drawing? 8. When first placing a slide on the microscope, what lens should you begin with? How should you proceed from there?
The$Compound$Microscope$ Student$Data$Pages$ Name: THE MICROSCOPE and letter "e" 1. Locate and learn each of the following parts of the microscope. Check them off the list below as you find them. Ocular Fine Adjustment Knob Coarse Adjustment Knob Rotating Nosepiece Arm Stage Clips Diaphragm Mirror Body tube Base Objectives 2. How many objectives does your microscope have? 3. How many times does each objective magnify? 4. Which objective is closest to the stage when it is pointing straight down? 5. Look for the number on the ocular. How many times does the ocular magnify? 6. How many lenses does the light pass through? 7. What is your total magnification using the 4x objective? The 10x objective? The 40x objective? 8. Does the stage move up or down? 9. Does the stage move up or down? 10. Is the image in the same position? If not, describe its position under the microscope. 11. Which way does the image move? 12. Which way does the image move?
13. Sketch of the "e with the 4x objective. Name of specimen Objective used to make drawing Estimated size of specimen 14. Is the field of view larger or smaller with the higher power objective? 15. Draw the "e" as seen under the 10x objective. Name of specimen Objective used for drawing Estimated size of specimen
16. What has happened to the size of your field of view? Draw the "e" as it appears under the 40x objective and label. Name of specimen Objective used for drawing Estimated size of specimen 17. As you changed objectives while looking at the "e", did the position of the "e" change? What happened to the field of view? What happened to the actual size of the specimen? 18. What is the diameter of the 10x field of view in microns? 19. What is the diameter, in microns, of the 40x objective? PROCEDURE: COLORED PAPER 1. How does this compare with the picture as seen with the naked eye? Make a sketch of the colored paper as it appears under the microscope. Name of specimen Objective used
2. What is resolving power (resolution)? 3. How can magnification help us? 4. How can resolution help us? 5. How can too much resolving power be a handicap? Final Observations: 1. Why should you never use the coarse adjustment knob while using the high power objectives? 2. Why must the bottom of slide and the stage be kept dry? 3. What is a parfocal microscope? What is the advantage of this? 4. What is the total magnification using the three objectives of your microscope?
5. What is the diameter of the field of view with each objective? 6. Was it easier to estimate the diameter of the letter e using the 10x or 40x objective? Why? Which estimate do you think is more accurate? 7. What three things should always be given with a drawing? 8. When first placing a slide on the microscope, what lens should you begin with? How should you proceed from there?