Focusing on a specimen takes time and patience. When done correctly, it can be a valuable tool to see things that are not possible to see with the naked eye. If you use the coarse-adjustment knob to focus on an object with the high-power objective lens you will encounter several problems. Since the coarse-adjustment knob is used to find the specimen, combining this with the high-power objective lens could cause you to move the stage too quickly and break the slide under the lens. It will all make it more difficult to find the specimen because the field of view is decreased the higher you go with the objective lenses.

Cells and the Microscope

All living organisms are made up of subunits called cells. Most cells are too small for the human eye to see, so we must use microscopes to see them.

The most common type of microscope used in biological labs is the compound light microscope. In this laboratory we will look at different types of cells under the light microscope.

In this laboratory we will learn to use the microscope. We will look at prepared slides and make "wet mounts". We will observe the differences in appearance between cells of different Kingdoms, and we will identify organelles visible with the light microscope.

GOALS

Identify the parts of the compound light microscope.
Learn to use the compound light microscope.
Learn to make a wet mount.
Draw and identify cells belonging to: Bacteria, Protists, Fungi, plants, and Animals.
Learn to identify plant organelles in the microscope.
Observe Osmosis in plant cells.

To Do:

A. Identify the parts of the microscope

B. Animal cells Follow instructions. Draw cheek cell / list total magnification on all drawings

C. Onion epidermis cells Prepare slide following instructions Draw cells

D. Cell Plasmolysis Draw plant cell before and after plasmolysis

E. Observe cells from the different kingdoms Draw a cell of each type excluding archaea

USE OF THE MICROSCOPE

1. Moving and carrying Always carry the microscope by holding the arm with one hand while the other firmly supports the base. Do not tilt the microscope or the eyepieces may fall off and be damaged.

2. Cleaning Wipe the stage after each use with absorbent paper. Use ONLY Lens paper to clean the eyepiece, objective lenses, and condenser lens. Any other type of paper may make permanent scratches.

If you use immersion oil, always completely clean the oil from the lens before moving to a lower lens, or storing the microscope. Otherwise, you will make a big mess. Use only lens paper to clean the lens glass.

3.Binocular eyepieces Binocular eyepieces can be adjusted to each individuals eye distance. If the image is not a full circle, or there is more than one image, adjust the distance by pushing the eyepieces together or pulling apart.

4. Objective lenses Always start and end your microscope session by placing the lowest power objective lens in position. This will make it easier to prevent crashing the objective lens into the slide.

5. Coarse and fine adjustment The coarse adjustment knob should only be used with the lowest power objective lens. Once it is in focus, you will only need to use the fine focus. Using the coarse focus with higher lenses may result in crashing the lens into the slide.

6. Stage controls The slide is placed on the stage between clamps. The dial on the right side contains two sets of controls. One that moves the stage up and down, and one that moves the stage side to side. The image viewed through the eyepiece is often inverted, so you may need to move the slide left for the image to move right, or move the slide up for the image to move down.

7. The condenser The condenser is a lens that focuses the light on the stage. Always start by setting the condenser diaphragm to the smallest size possible and open it slowly until the slide is illuminated correctly. The condenser can help prevent the image from appearing washed out.

Directions for microscope use

1. Plug in and turn on the lamp. Turn the light to a medium high power.

2. Make sure that the lowest powered objective lens is down. Lower the stage to its lowest setting.

3. Position the slide in the clamps. Use the stage controls to make sure that the image is centered. It should be positioned below the objective and in the path of the light.

4. If a condenser is present, set the aperture dial on the lowest setting. (smallest opening).

5. Looking in the eyepiece, slowly move the coarse adjustment knob to find the specimen. If you are unsure that you are looking at the slide, move the slide from side to side. If the specimen is thick, begin by focusing on the side of the specimen and then moving the slide to the center.

6. Adjust the light for the best viewing using the condenser knob, and the light level controls.

7. To use a higher powered objective, click the new objective into position, and then refocus using the fine adjustment knobs. Always look when turning objectives to prevent crashing the lens into the slide.

8. When you are in focus, use the stage controls to scan the field and find a good example to observe.