Using Microscopes

Part 2

Stereomicroscopes

  1. Carefully remove the stereomicroscope (two eyepieces) from under your lab table. Always keep the cover on the microscope when it is not in use.
  1. What is the magnification of the lowest power?______Highest power?______
  1. How does the working distance affect the size of objects that can be viewed under the stereomicroscope compared to the compound microscope?
  1. Lay your hand on the stage of the stereomicroscope. Focus on the back of your hand and draw exactly what you see in color.

Specimen______

Magnification______

  1. Compare the movement of your hand seen through the eyepieces to the direction you moved your hand. Is it the same as in a compound microscope? Explain.
  1. Compound light microscopes work by having light pass through the objects to be viewed. However, not all objects are translucent (see through). Some objects are opaque (not see through); light cannot pass through them. Make wet mounts of an onion skin with iodine stain and a small piece of leaf. Observe both under low power.
  • How does your view of onion skin compare to your view of the Leaf?
  • If an opaque object is viewed through a compound light microscope, what will you see?
  1. Place a leaf under the stereomicroscope. Focus on the highest power and draw exactly what you see in color.

Specimen______

Magnification______

  1. How come you can see the leaf with a stereomicroscope, but not with a compound light microscope?
  1. Place either a coin or paper money under the stereomicroscope and focus on the eye of the person on the money. Draw exactly what you see in color.

Specimen______

Magnification______

Review of Microscopes

  1. Under which power, high or low, is the largest field of view?
  1. What happens to the field of view when you switch from low power to high power?
  1. Why do objects look three-dimensional under a stereomicroscope but not under a compound microscope?
  1. If a microorganism were swimming from right to left across your field of view under a compound light microscope, which way would you move the microscope slide to keep it in view? Why?
  2. If the same microorganism as above were swimming from right to left across your field of view under a stereomicroscope, which way would you mover the microscope slide to keep it in view? Why?
  1. Take a sample of pond water and make a wet mount. Look for moving organisms under high power. Find two different kinds of microorganisms and draw them in color.

If the microorganisms are moving too fast, add a drop of slowing solution to your sample.

Choose a minimum of any THREE extra specimens to examine. Make sure you write down the name of the specimen and the magnification used for best viewing. Below you will find a list of ideas, but anything that has microscopic structure will work.

Possible specimens:

  • Cheek cell stained with methylene blue
  • Scrape the inside of your cheek with a tooth pick
  • Rub the goo you collect on a slide and mix with a drop of methylene blue
  • Yeast cell stained with methylene blue
  • Onion skin stained with iodine
  • Cork slice
  • Pollen grain
  • Aquarium rock water

Anything else?