Determine the Position of an Object When Viewed Through a Microscope

Name______Date______Period______Microscope Lab Several important techniques and ideas must be mastered to use a microscope. Just knowing that a microscope magnifies things and knowing how to prepare a wet mount are not enough. Knowing how and why your microscope works will enable you to use it better. The techniques and hints presented in this investigation will help you use your microscope correctly.

Objectives  Determine the position of an object when  Find the proper depth of field for objects. viewed through a microscope.  Prepare a wet mount properly.  Use the diaphragm correctly.  Make proper scientific drawings.

Materials Microscope Medicine dropper Water in a beaker Microscope slide Scissors Cover slip Thread, 2 different colors Newspaper Absorbent cotton

Background Information Rules for Microscope Use 1. Always carry the microscope in front of your body with two hands: one holding the arm and the other supporting the base. 2. Always start out with the lowest power objective (4x, red), center and focus your object, then move up to the traditional low power objective (10x, yellow). Focus again before moving up to high power (40x, blue) objective lens. 3. Always use the fine adjustment knob under high power and never the coarse adjustment knob which is to be used only on low power. 4. Always store the microscope on low power with the stage as far down as possible. 5. Always return the slides to their proper location for storage and never put the microscope away with a slide on the stage. 6. Always turn the microscope off before unplugging. 7. Use only lens paper to clean the lenses. 8. Never drag the microscope across the desk. Place away from the edge of table/counter.

Rules for Scientific Drawings 1. Use white unlined paper and use a pencil to draw & shade and colored pencils to color (if required). 2. If you are drawing a specimen from a microscope, draw a circle to represent the field of view and make your drawing to scale. 3. The name of the specimen should be centered and underlined at the top of the drawing. 4. Lines for labels extend from the diagram to the right and should be parallel and end at the same point on the page. 5. Labels are printed beside the line, not above it. 6. The magnification (if applicable) should be centered below the drawing. To determine magnification: 1. Multiply the power of the eyepiece (ocular) lens by the power of the objective lens. The power of each is written on each lens. 2. Eyepiece= 10x; Super Low Power (red)= 4x; Low Power (yellow)= 10x; High Power (blue)= 40x. 7. BE AS NEAT AS POSSIBLE. Example of a correct scientific drawing: Example of an incorrect scientific drawing: Anacharis

40x

10x

10x Use 4x to focus, then move to 10x for low power

40x Use 4x to focus, then 10x , then up to 40x for high power

2 Procedure Part A. Position of Objects When Viewed With a Microscope 1. Prepare a wet mount of a lower case letter “e” from a piece of newspaper. a. Cut out an “e” and place the letter “e” on the slide. Position the cut out “e” so it faces you as it would on a newspaper page. b. Put a drop of water on the “e”. c. Place the cover slip over the “e” by placing at a 45o angle over the letter “e” and gently lowering it on top of the “e”. Be careful not to trap air bubbles under the coverslip. 2. Place the wet mount of the letter “e” onto the microscope stage. Position the slide on the stage so that the “e” faces you as it would on a newspaper page. 3. Observe the “e” using LOW POWER (start with 4x, then move to low power 10x objective lens) on the microscope. Focus the “e” with your coarse adjustment knob, then with the fine adjustment.

a. Circle the letter “e” that looks like your letter “e” when viewed on low power.

b. What is the position of the “e” viewed with the microscope compared to its position on the stage? ______

4. While looking through the eyepiece, move the slide slowly from LEFT to RIGHT. a. What direction does the letter move as seen through the microscope? ______

5. While looking through the eyepiece, move the slide slowly from RIGHT to LEFT. a. What direction does the letter move as seen through the microscope? ______

6. While looking through the eyepiece, move the slide TOWARD YOU. a. What direction does the letter move as seen through the microscope? ______

7. While looking through the eyepiece, move the slide AWAY FROM YOU. a. What direction does the letter move as seen through the microscope? ______

8. Viewed with a microscope all objects will be oriented in a manner similar to the “e”. a. How will all objects appear under the microscope in relation to their true position on the stage? ______b. How could you position objects on the microscope stage so they are viewed right side up? ______

Before starting Part B, throw away your “e” in the trashcan, dry your slide and clean up.

3 Part B. Use of the Diaphragm 1. Prepare a wet mount of a few strands of cotton. (Follow Procedure Part A #1) 2. Observe the cotton fibers with LOW POWER (10x obj lens). While looking through the microscope, change the amount of light entering the microscope by adjusting the DIAPHRAGM. (move wheel at far end of stage). a. Under what diaphragm setting are the cotton fibers sharpest? Circle one. 1 (little light) 3 (medium light) 5 (maximum light)

3. Change to HIGH POWER (40x obj lens) and observe the cotton fibers (Remember DO NOT use the coarse adjustment knob on high power, only use the fine adjustment knob to focus.) Again, readjust the amount of light entering the microscope by changing the diaphragm. a. Under what diaphragm setting are the cotton fibers sharpest? Circle one. 1 (little light) 3 (medium light) 5 (maximum light)

4. All objects viewed under the microscope will require adjustment of light. Many problems associated with microscopic observation can be overcome by adjusting the diaphragm for proper lighting.

Before starting Part C, throw away your cotton in the trashcan, dry your slide and clean up.

Part C. Depth of Field 1. Obtain a pre-made slide with threads (DO NOT put water and a cover slip over them). 2. Locate the strands under LOW POWER. Center the slide so you are looking at the point where the strands cross. Adjust the diaphragm for proper lighting. a. Can both strands be seen clearly at the same time under low power? ______3. Change to HIGH POWER and observe both strands where they cross. a. Can both strands be seen clearly at the same time under high power? ______b. Explain why it is impossible to observe objects clearly at different depths at the same time when on high power. ______

Make sure everything is neat for the next class. Turn off the microscope, unplug it, and wrap the cord neatly securing it with the zip tie.

Raise your hand when your group is finished cleaning up for the teacher to come and release you from your lab station.

Make sure your name, date, and period are at the top of the paper and turn it in to the area designated by your teacher.