Introduction to the Microscope

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1 Title: Microscope Mania "Micro" (Greek!) refers to tiny, "scope" refers to view or look. Microscopes are tools used to enlarge images of small objects so they can be studied. The compound light microscope is an instrument containing two lenses, which magnifies, and a variety of knobs to resolve (focus) the picture. Because it uses more than one lens, it is sometimes called the compound microscope - in addition to being referred to as a light microscope. Purpose: to learn about the proper use and handling of the microscope and practice looking at a variety of specimen with a microscope. You will need: Compound microscope Glass slides Cover slips Eye dropper Microscope diagram The letter "e" cut from newsprint Scissors various specimens to examine Procedures I. Microscope Components and Handling 1. Carry the microscope with both hands --- one on the arm and the other under the base of the microscope. Go to the microscope storage area and properly transport one microscope to your working area. Remove the dust cover and store it properly. DO NOT plug it in or turn it on until instructed. 2. Examine the microscope. Use a microscope diagram sheet and information provided by your teacher to fill in the names and functions of each part listed on figure Attach the completed diagram in your lab journal. II. Determining Total Magnification Fig. 1.1 There are numbers stamped on the eyepiece and on each objective lens. Locate these numbers. You will use these to calculate the total magnification when using each lens. You calculate by using the steps below. 1. What is the magnification written on the ocular lens (eye piece)? 2. What is the magnification written on: a. the low power objective b. the medium power objective c. the high power objective

2 3. The total magnification is determined by multiplying the objective lens power with the ocular lens power. Copy the table below into your notebook and then calculate the powers of magnification for each objective lens. Band color Eyepiece lens power Objective Power (X) = Power of Magnification (X) = (X) = You are now ready to observe specimens using the microscope. You can do the following procedures (III-VI) in any order. You only need to complete 3 of the 4 procedures, so choose which ones most interest you! Be sure to record in your lab notebook what procedure number you are completing. III. Observing Specimens 1. Select a slide for viewing from those provided. Place the prepared slide on the center of the microscope's stage, directly over the clear hole. Put one stage clip on one edge of the slide to hold it in place leaving the other end free to move around. Turn your microscope's light source on, lower the stage, and position the lowest power objective lens over the slide. 2. Looking through the eyepiece, turn the coarse focus knob until the outlines of the specimen becomes visible. Then turn the fine focus knob to get the image as sharp and clear as possible. The basic shape of the specimen should be visible on low power. Now turn the nosepiece so the 10x objective is positioned over the stage. 3. As you slowly turn the fine focus knob you are actually moving in and out of many layers of the specimen, which is why some parts in the field of view may look blurry while some are sharp. This is simply because you are looking at a three-dimensional object and at high magnification the different layers seem much larger than they would without the magnification, even in tiny single-celled organisms! 4. In your notebook, cut out and paste a Microscope Mania drawing sheet. Fill in the sheet with the specimen name and power. You do not need to put your name on the sheet. 5. Make 3 drawings of the specimen, one on low power, one on medium power and one on high power be sure to identify the total magnification under each drawing. Use colored pencils to more accurately show what you are seeing. You will need a total of 3 Microscope Mania quarter sheets. 6. Now select one more prepared slide from those available. Sketch it at the highest magnification that is practical. Be sure to label your drawings and indicate the magnification use color as well. You will only need one Microscope Mania sheet to complete this step. **You should have a total of 4 drawings from this station One specimen drawn at low, medium and high (for a total of 3 drawings) and one drawing of a prepared slide at high magnification.**

3 IV. Preparing a wet mount of the letter "e. 1. Cut out a letter "e" from the pieces of newspaper provided. 2. Place it on the glass slide so it looks like an (e). Figure Make a wet mount of the letter e. *See diagram on the last page for instructions on how to make a wet mount. 4. Make sure the low objective is pointed toward the stage. Turn on the microscope and place the slide on the stage; making sure the "e" is facing the normal reading position (see the figure above). 5. Using the course focus, on low power, focus until the "e" can be seen clearly. Use a slide Microscope Mania information/drawing sheet record your observations and draw what you see. Draw it exactly how it appears in the microscope. Does it take up the whole circle, part of the circle or some of the circle, etc. 6. Be sure you label all your drawings with the total magnification represented. 7. As you are looking through the eyepiece, move the slide to the upper right area of the stage. Describe what happens. Now, move it to the lower left side of the stage. What direction does the image move? Record these observations in your notebook. 8. Re-center the slide and change the objective to medium power. You will notice the "e" is out of focus. DO NOT touch the coarse focus knob, instead use the fine focus to resolve the picture. Draw the image you see of the letter e (or part of it) on high power. Use a Microscope Mania sheet to complete this step. 9. Locate the diaphragm under the stage. Move it and notice the changes in light intensity as you do. 10. Remove the slide. Carefully remove the cover slip. Throw away the e, rinse the slide and cover slip and carefully dry them with a small piece of paper towel. **You should have a total of 2 drawings/descriptions for this station: one from #5, and one from #8.** V. A Hair s Width 1. Make a wet mount with a few 1/4" to 1/2" pieces of human hair from one person using a drop of water on a slide, and cover with a cover slip. *See diagram on the last page for instructions on how to make a wet mount. 2. Observe the hair, draw and write a description of it on a Microscope Mania observation/drawing sheet. Look at the end that came from the head of a pulled hair (the root). Record what you see on another observation/drawing sheet. Draw what you see on medium power. 3. Repeat this with a sample of a different colored hair. Record what you see on another Microscope Mania observation/drawing sheet. Draw what you see on medium power. 4. Find someone with hair that is dyed. Make a wet mount sample and observe/draw. Are there any differences compared to natural hair that hasn t been colored? **You should have a total of 4 drawings/observations from this section: 2 from #2 (the hair and the root), 1 from #3 (the different colored hair only, not a drawing of the root), 1 from a dyed hair specimen.**

4 VI. Spice it Up 1. Prepare a dry mount of a sample of salt, sugar and pepper. For each sample, transfer a small amount onto the slide with tweezers. Remember to start focusing on low power! 2. Under low power, observe the salt crystals. Focus on medium and then high power. Use a Microscope Mania sheet to draw what you see. 3. Examine the sugar sample. Use a Microscope Mania sheet to draw what you see on high power. 4. Examine the pepper sample. Use a Microscope Mania sheet to draw what you see on high power. 5. Now choose another spice, make a dry mount and record your observations on high power using a Microscope Mania sheet. **You should have a total of 4 drawings/observations from this section: 1 each from step #2-#5** When you are finished with a microscope - turn it off. Clean up your slides and cover slips and return them to the box. Place the low power objective in place and lower the body tube. Cover the scope with the dust cover. Place the scope back in its proper place. How to Prepare a wet mount for a specimen Procedure 1. Place the specimen on the microscope slide. 2. Place one drop of water on the center of the specimen. 3. While holding the cover slip upright, carefully place one edge of the cover slip next to the water. 4. Slowly lower the upper edge of the cover slip onto the water. The objective is to minimize or eliminate air bubbles under the cover slip. 5. After you have covered the specimen with a cover slip, an absorbent towel can be placed at the edge of the cover slip to draw out some of the water, further flattening the wet mount slide.

5 Conclusions: Answer the following questions in your notebook. You only need to answer the questions about the procedures you did. The answers are based on the work you have just completed using the microscope. Questions (Observing Specimens) 1. What difficulty did you have when you observed your samples under the microscope? 2. What surprised you about what you saw under the high power that you couldn t see under low power? Questions (The letter e ) 1. What happens to our view of an image as you increase the power of magnification? 2. What did you observe about the orientation of the letter e when viewed through the microscope? 3. Why would you want to wet mount a specimen? Questions (A hair s width): 1. Did you see any differences between the hair that had been dyed and that which was a natural color? 2. Describe what the root looked like. Did this surprise you? Questions (Spice it up) 1. What does table salt look like? 2. What did the sugar look like? 3. What was unique about the spice you chose? 4. Why did you need to make a dry mount of these instead of a wet mount?

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