First exercises in how to use a microscope correctly

 

Pick one of the following exercises, then go on with the ‘real’ specimens (plant and animal cells).

 

A.               Letters

 

Material: microscope, glass slides, coverslips, glass rod (Glasstab), a glass of water, newspaper, tweezers, paper, pencil, eraser/rubber, paper tissue or cotton cloth

 

1. Cut out a letter from the newspaper (preferably ‘ü’ or ‘ä’).

2. With the glass rod transfer a drop of water onto the slide. Then add the letter to the drop of water. Cover with a coverslip as described in the instructions on how to make a wet mount.

3. Focus with the scanning objective and adjust the diaphragm to achieve the best contrast.

4. Move the slide a little to the left while you look through the microscope, then a little away from you. What happens to the image?

5. Center the specimen again. Switch from the scanning to the low power and then (carefully!) to the high power objective. What changes occur as you watch, for example, the dot on the letter?

6. Switch back to the scanning objective and get the letter in focus. Carefully remove the eyepiece. How far away do you have to place your eye to see the letter in focus? Why is this so?

7. Place a piece of transparent paper over the opening of the body tube so you get a focused image of the letter on the paper. Describe the image.

8. Note down all your observations.

 

 

B.      Sand grains

 

Material: microscope, glass slides, coverslips, glass rod (Glasstab), a glass of water, grains of sand (Sandkörner), tweezers or long needle (Lanzettnadel), paper, pencil, eraser/rubber, paper tissue or cotton cloth

 

1. With the glass rod transfer a drop of water onto the slide. Then add a few sand grains to the drop of water. Cover with a coverslip as described in the instructions on how to make a wet mount.

2. Compare the forms and sizes of the grains.

3. How can you find out about the three-dimensional structure of the grains?

4. Often there are air bubbles trapped in the wet-mount. How does an air bubble look like under the microscope when you see it in cross-section (Querschnitt) / when you look directly at its surface? Make a sketch.

5. Write down your observations.

6. Make a drawing of a sand grain. Don’t forget to write down the magnification and the name of the specimen.