Tools of Magnification
Using the Microscope
Students should begin the focusing procedure by moving the low power objective into place. Then, each student should center his or her slide over the opening in the microscope stage and secure the slide with the clips on the stage. If the microscope has a light source, be sure students have the light aimed up through the paper in the slide.
Initially, the diaphragm should be adjusted to its largest opening. Delicate objects require less intense light than more dense objects and materials, and if the image is too bright (seems washed out) when viewed through the microscope, help students reduce the amount of light by partially closing the diaphragm.
NOTE: Low-power dissecting type microscopes may not have a light source below the stage.
With the lowest power objective in place above the print material on the slide (not all microscopes have multiple objectives), have students use the coarse focus knob to move the tip of the objective as close to the cover slip as possible.
Instruct students to look through the eyepiece and use the coarse focus (depending on the microscope) knob to move the objective gradually away from the paper until the print comes into view. Remind students that the sample will come into focus when the objective is very close to the stage.
Tell students to use the fine focus knob to sharpen the appearance of the image further. The newsprint on the slide should be centered in the field of view. Each student should have an opportunity to adjust and focus the microscope.
After drawing their observations of the printed material on the "Magnification Observations" student sheet, some students may wish to study the newsprint at a higher magnification. Instruct students to gently rotate the middle magnification objective into position over the slide and adjust the focus using the fine focus knob only. This objective is longer and will come closer to touching the surface of the cover slip, so students must use caution not to break the cover slip.
- Moreno, N., Tharp, B., Erdmann, D., Rahmati Clayton, S., Denk, J. (2008). The Science of Microbes Teacher’s Guide. Houston, TX: BioEd.
- Caprette, D. (2005). Light microscopy: Instrumentation and principles. BioEd Online. Baylor College of Medicine: Houston, TX.
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Grant Number: 5R25RR018605