Lab Exercises

In this laboratory, you will examine a variety of specimens in order to learn good microscope technique. You will perform activities that demonstrate the key concepts of magnification, resolution, slide manipulation, field of view and depth of field.

Observations on the letter "e".
When a slide of the letter "e" is placed on the microscope several observations can be made. The picture below illustrates the orientation of the letter "e" viewed with the microscope. How is it different from what you might have expected? Try drawing the letter "e" rightside up and then as it appears here. Furthermore, if you move the slide to the left across your microscope stage, the letter "e" seems to move to the right. What will happen if you move the slide away from yourself?

Total Magnification of 40X Total Magnification of 100X

Next, observe the letter "e" with a higher magnification lens. The fine texture of the paper should be more visible. Additionally, some of the letter "e" is now missing from your field of view, since the specimen is too enlarged for you to see all of it at one time. This explains why you must carefully center small specimens within your field of view, before changing lenses. The higher the magnification of the objective lens, the smaller the field of view.

Depth of Field
This concept can be understood by focusing on three overlapping colored threads. Notice the textural details visible in the yellow thread. Both the red and blue threads are out of focus. Because the red and blue threads lie either below or above the yellow thread, they are in a different plane of focus. To determine the relative position of all 3 colored threads, you must raise and lower your objective lens slowly (known as "focusing up and down") and observe the order in which the threads go in and out of focus. As your objective lens approaches the slide, the first thread to come into focus is on the top. Understanding the concept of depth of field will help you visualize the structures within a thick section of tissue or a large single-celled organism.

Continue on to Lab Quiz.