In This Activity, You Will Do the Following

Name ______Date ______Block ______

In this activity, you will do the following:

• Label and describe the functions of the parts of a compound light microscope
• Calculate total magnification and measure specimen through a light microscope
• Observe and draw specimen as seen through a light microscope

1. microscope labeling and function

Label and briefly describe the function of each microscope part.

II. Using the Microscope

1. Always locate your specimen using the ______power objective lens.
2. Focus your specimen first with the ______adjustment knob, then sharpen the image with the ______adjustment knob.
3. Without turning the knobs, rotate the nosepiece to the next objective lens. Then sharpen with the ______adjustment knob.
4. When finished using the microscope, always return the nosepiece to the ______power objective lens, remove the slide and cover the microscope.
5. Always carry the microscope ______.

III. TOTAL MAGNIFICATION:

The total magnification of the specimen is calculated by multiplying the magnification of the eyepiece by the magnification of the objective lens. Complete the following table.

IV. Using a Light microscope

1. Prepare a wet mount of the letter “e” on your microscope slide. Add a cover slip and examine under low power. Make a drawing under low power, using pencil only. Your drawing should represent accurately the field of vision.

1. When you view the letter through the microscope, how does it appear? ______
2. Find the diaphragm. Look through the eyepiece as you turn the diaphragm. What do you observe?

______

1. Look into the eyepiece and twist it left and right. Notice the line inside that rotates as you twist. What do you think is its function? If your microscope does not have a line, find one that does.

______

1. View the specimen through the microscope and have your partner push the slide to the left. Which direction does the “e” appear to move? ______

1. What happens when you move the microscope slide away from you? In what direction does the “e” move? ______

1. View the specimen under Medium and then High Power. Make an accurate drawing in pencil under the power of your choice.

V. MEASURING THE FIELD OF VIEW:

When you look through the microscope, the “circle of light” that you see is called the field of view. Knowing the diameter of the field can help you estimate the sizes of the specimen you are viewing.

Place a clear ruler on the stage. Looking through the microscope, focus on one of the lines. Position the ruler so that one of the vertical lines dividing the ruler in millimeters is just visible at the left edge of the field of view. The distance between the first and second vertical lines is 1mm. How many mm can you see in your field of view? ______

Make a drawing under low power.

a. If each millimeter is equal to 1000 micrometers (m), what is the diameter of your field of

view under low power in micrometers? ______

b. Switch the objective lens to medium power. Use the clear ruler as you did earlier. What is the diameter in mm? ______What is the diameter in m? ______Make a drawing under medium power.

c. The high power objective has a field of view approximately 450 micrometers. Why would it have been difficult for you to use the plastic ruler as you did under lower power and medium power? ______

d. What are the benefits of using a high magnification? What are the drawbacks? ______

VI. Depth perception

1. A compound microscope lacks depth perception. It is capable of focusing on only one layer at a time. To see this, cut two threads, a light color and a dark color, so they are no longer than 2 cm. Without letting your partner see, cross the threads on a slide and make a wet mount. Have your partner view the slide under low and then medium power. Determine which thread is on top by first lowering your stage all the way. Slowly raise it until a thread comes into focus. The first thread to focus is the one on top. Check your results with your partner!

c. Draw the threads as they appear under low and medium power.

a. Under medium power, estimate the thickness of the threads in m. ______

VII. Explore

Choose at least two other specimens offered or approved by your teacher. Sketch your specimen under low and medium power. Label your specimen and determine the total magnification. Also, estimate the length or diameter of the specimen. Check your estimation: It should be the same whether through low or medium power!

VII. Analysis

Match the microscope parts with their functions.

_____ diaphragma. brings objects slowly into sharp focus

_____ eyepieceb. brings objects into rapid but coarse focus

_____ stagec. regulates amount of light entering microscope

_____ fine adjustmentd. is attached to revolving nosepiece and contains a lens

_____ low power objective capable of 4X magnification

_____ nosepiecee. contains a lens capable of 40X magnification

_____ coarse adjustmentf. supports slide

h. turns to change from one power to another

i. contains a lens capable of 10X magnification

VII. Conclusion: Describe the data a microscope enables a scientist to gather. What microscope functions can you use to help you view your specimen more clearly?

______

______

______

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