Name: ______Date: ______

Activity: Observing a Newsprint Letter e

Goals:

  1. To use a microscope to observe a newsprint letter e.
  2. To find a specimen using the low, medium, and high power objectives of a light microscope.
  3. To discover what happens to the image of a specimen when using a microscope.

BackgroundInformation:

Microscopes are very important tools in biology. The term microscope can be translated as “to view the tiny,” because microscopes are used to study things that are too small to be easily observed by other methods. The type of microscope that we will be using in this lab is a compound light microscope. Light microscopes magnify the image of the specimen using light and lenses. The term compound means that this microscope passes light through the specimen and then through two different lenses. The lens closest to the specimen is called the objective lens, while the lens nearest to the user’s eye is called the ocular lens or eyepiece.

When you use a compound light microscope, the specimen being studied is placed on a glass slide. The slide may be either a prepared slide that is permanent and was purchased from a science supply company, or it may be a wet mount that is made for temporary use and is made in the lab room.

The microscope is an important tool and a serious scientific instrument for the biologist. It is also fun to use it to look at everyday things. Discovering what common objects look like under magnification is often surprising. By looking at a printed letter e under the microscope, you can practice focusing a microscope, find a specimen using all three objective lenses, and enter the microworld at the same time!

Materials: One lower case letter e in a strip cut from computer paper or newsprint, scissors

Procedure:

Place the strip of lower case letters in front of you. Be sure the letters are facing in the proper direction for reading – right side up!

  1. What I Know: Write a sentence or two about what you already know about how a microscope works.
  1. In the left-hand circle below, draw one letter e as you observe it with your unaided eyes.
  2. Click the low power objective (4X) in place under the body tube of your microscope. Use the coarse adjustment knob to raise the body up as far as it will go.
  3. Center the letter e over the stage opening. Use the stage clips to hold the slide in place.
  4. Use the coarse adjustment knob to focus the letter e. Draw what you see in the right-hand circle below. Be sure the pointer in your field of view is touching some part of the letter e.
  1. Click the medium power objective lens (10X) into place. Adjust the focus with the course adjustment knob. (Normally, you would not use the coarse adjustment for medium power, but for a newsprint slide it’s acceptable.)
  2. Draw what you see in the circle below.
  3. Click the high power objective (40X) into place. Use the fine adjustment knob ONLY to focus the letter e.
  4. Draw what you see in the labeled, right-hand circle below.
  • What happens to the image of the letter “e” as you go from low power to medium power to high power?
  1. Refocus your specimen in medium power. Slowly adjust the diaphragm under the stage to the appropriate light for viewing.
  • What happens as you adjust the diaphragm?
  1. As you look into the microscope, use your fingers to move the slide to the right and then to the left.
  • What happens to the image as you move the slide to the right?
  • What happens as you move the slide to the left?
  • Move the slide up, what happens?
  • Move the slide down, what happens?
  1. Analysis:
  1. How does the letter “e” as seen through a microscope differ from the way an “e” normally appears?
  1. How does the ink appear under the microscope compared to normal view?
  1. Why does a specimen place under the microscope have to be thin?

d. When is a microscope a useful tool for a biologist?