Roxane Ohl - Aug 15, 2019

Helping Students to Use a Microscope

by Roxane Ohl

Have students identify where the tissue is on the slide they wish to view and position the slide on the microscope stage, centering the tissue under the lowest powered (4X) objective lens. While they view from the side, have them move the objective lens as close to the cover glass as possible without touching the glass. While viewing through the microscope, have them slowly draw the objective lens away from the specimen using the coarse focus.

When they have the tissue in view, have students stop and use the fine focus to sharpen the image of the cells at the lowest magnification, then switch to the next higher objective lens and refocus. At this point they should only need to use the fine focus. From here, have students work up to the objective lens giving the magnification level required to view the specimen at the detail desired.

 

The underside of a leaf viewed at 400X total magnification

 

The underside of a leaf viewed at 400X total magnification. Note the paired guard cells surrounding each stoma.

It is a thrill for students to view tissue from plants they grow themselves. Students should be able to differentiate chloroplasts and guard cells (stomata) in fresh wet mount leaf specimens using the 10X objective lens (100X total magnification). Stomata are easier to see from the underside of the leaf. They are fairly well visualized at 400X magnification. Be sure to teach students to adjust the diaphragm to get the optimal/maximum amount of light.

Written by Roxane Ohl