Bacteriology 102: Using the Phase-Contrast Microscope

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Here are quick and easy directions for using the phase-contrast microscope for viewing wet mounts of living specimens. As these are already set up by the instructor, all one has to do is insert the slide and then focus with the 40X objective (without oil) – starting as low as possible and then focusing up. That's it. As time permits, we will get into the optics of phase-contrast microscopy and what it takes to adjust the lens systems for optimal high-contrast observations.

This page covers the same procedures as the handout passed out on the first day of lab. Match the numbers on the following steps to the numbered parts on the photo.

1  Objective lenses: Do all focusing and observing with the 40X objective lens (at least through the first half of the semester). Usually this is the lens already in place, having been used by the instructor to align the optics.

2  Stage: Insert slide as shown in the diagram below. The slide is secured on its sides, and the clamps do not ride over the slide.

3  Keep this unit pushed in! Never pull it out as doing so defeats the whole purpose of using the phase-contrast microscope. Instructor can explain.

4  Coarse adjustment knob: Looking from the side, use the coarse adjustment to bring the slide and lens as close together as possible without touching.

5  Fine adjustment knob: Looking through the microscope, use the fine adjustment to bring the image into focus.

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Page last modified on 9/15/02 at 6:00 PM, CDT.

John Lindquist, Department of Bacteriology

University of Wisconsin – Madison