Using a Microscope 1

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LAB: Using a Microscope

Part 1. Who uses microscopes?

Glencoe (2002) Chapter 2.2 Viewing Cells

People use microscopes to see things that are difficult or impossible to see with the “naked eye.” For example, doctors use microscopes to watch microbes, to identify disease organisms, to learn how molecules work together, and to witness how brain cells transmit impulses through the nerves. Manufacturers of drugs examine how cells produce chemicals, and how cells react to ingested drugs. Manufacturers build machines in the nano-scale. Forensic investigators study evidence. For example, they can tell from viewing a hair at high magnification whether it was pulled out or fell out on its own. Gemologists examine the crystalline structure of rocks and minerals.

The microscope has improved since it was first invented in the 1500s by a maker of reading glasses.

By 2015, microscopes became able to image objects a million times smaller than a human hair (Turk). We can now see single atoms.For this lab, will be using compound light microscopes. The maximum magnification of our school machines is 400x life size.

1. Explain what “compound” means.

Part 2. What are the parts of a microscope?

Glencoe (2002) Reference Handbook p. 859

2-13. Label the parts on of a microscope on the diagram below, using all the words from this word bank.

armcoarse adjustment cover slipeyepiece slide fine adjustment diaphragm clip illuminator stage high-power objective lens low-power objective lens

Part 3. How does a microscope operate?

Watch “How to Use a Microscope” at (6.20min)

Setup

  • Use one hand to grasp a microscope by its arm, and use your other hand to support its base.
  • Set the microscope on a table with its arm facing away from you.
  • Unwind the cord, and plug in the microscope.
  • Turn on the microscope light, also known as the illuminator.
  • Lower the stage as far as possible using the coarse adjustment knob.
  • Turn the revolving nose piece to move the low power objective lens (4X), which is the shortest lens, over the light source.

Use

  • Secure the prepared slide to the stage using the stage clips. Some microscopes allow you to move the slide around in different directions.
  • Start with the lowest magnification.
  • Bring the slide image into focus by turning the adjustment knobs (first the coarse knob, then the fine adjustment knob).
  • Adjust the amount of light shining up through your sample using a wheel or similar tool under the stage, known as the diaphragm. Brighter is not always better.
  • To view your specimen at a higher magnification, lower the level of the stage, then rotate the nose piece so that a high-power objective lens is over your specimen. Look through the eyepiece lens to see the final enlarged image. Re-focus with the fine adjustment knob.

Care

  • Set the low power lens over your specimen.
  • Lower the stage as far as possible.
  • Carefully remove the slide from the microscope, and clean off any debris left on the microscope with a tissue or paper towel. Check if the slide or cleaning paper require biohazard treatment or disposal.
  • Turn off the light.
  • Unplug the microscope.
  • Wrap the power cord around the arm.
  • Carry the microscope to its storage place.

Part 4. Use a compound light microscope

Consider the light source for a microscope.

14. A “light” microscope uses light to view an image. Where does this light energy come from? Name two possible sources.

15. What part of the microscope controls the amount of light that shines on a slide?

16. How is this part of a microscope similar to the human eye?

Examine animal and plant cells with the microscope, using two slides that you make yourself.

“Cheek Epithelial Cells: How to Prepare a Wet Mount Microscope Slide” at .

“Onion Skin Epidermal Cells: How to Prepare a Wet Mount Microscope Slide”at

Glencoe Life Science (2002) Chapter 2.1 “Cell Structure”

17-20. Draw both images below. Label at least two parts of each cell.

Cheek cell / Onion epidermis cell

21. How much magnification did you require to see these cells clearly?

Consider depth of field. This means, how can you see layers, or one structure on top of another? Examine four slides prepared with three threads of different colors lying across each other.

22. Which two slides are the same—with the same color thread on top, in the middle, and on the bottom?

23. Consider the direction of an image seen with our microscopes. Bunny Hoest and John Reiner have authored a series of “Howard Huge” comics. Examine a “Howard Huge” comic under the microscope. Write here how the title appears in the microscope.

24. In what two ways do our microscopes change the direction of an image?

25-28. Draw a diagram of another image you view with a microscope. Use a prepared slide (we have feathers, leaf cross-sections, stems, human hair, human tissues, fingerprints, and diatoms) or make a slide from an object that you bring in from home. Make sure that you stay safe and sanitary in terms of chemicals used, sharp edges, etc. Check with your teacher if you have any concerns. Identify your object, the magnification you used for this diagram, and its key parts. Describe below how at least two of the key parts work. Cite any online sources used.

Sources

"How Are Microscopes Used Today?"Reference. N.p., n.d. Web. 20 Feb. 2017.

Thorsten, C. "CR Scientific: Microscopy Experiments: The Five-Minute Food Color Stain."CR Scientific: Microscopy Experiments: The Five-Minute Food Color Stain. CRS CR Scientific LLC, Mar. 2007. Web. 20 Feb. 2017.

Turk, Victoria. "This Microscope Can See Down to Individual Atoms."Motherboard. N.p., 11 Mar. 2015. Web. 20 Feb. 2017.