Using a Microscope
In order to view objects that are not visible to the naked eye, we will be using
a compound light microscope. This requires you to make slides of the object
you wish to view and cover them with cover slips. Read some basic rules of
microscopes below and see what slides we will be preparing in lab.
Microscope Rules
You should have the parts of the microscope labeled before beginning lab
today. There are 2 important rules to remember when using your
microscopes:
1. Always carry your microscope with one hand on the arm and the other under the base.
2. Begin by using the low power objective lens (usually yellow) and focusing your slide
with the
coarse adjustment. When the object is clear, carefully switch to the high
power objective (blue) and
USE ONLY THE FINE ADJUSTMENT to focus.
Viewing slides- newspaper letter
1.
Obtain a letter “e” slide.
2.
Place the slide in the center of the stage of your microscope with the low-power objective (yellow) in
place. Keeping both eyes open, look through the eyepiece and focus using the coarse adjustment. Make a
sketch of the letter under low power on your paper, labeled: Letter – Low power.
3.
Move your “e” slide to the left. Which direction does it move under the microscope? ___
4.
Move your “e” slide up. Which direction does it move under the microscope? ________
5.
Center your “e” while looking through the eyepiece.
6.
Without moving anything, carefully switch to the medium power objective and use the fine focus to
correct any blurriness. Then switch to high focus. DO NOT USE THE COARSE ADJUSTMENT ONCE
YOU ARE ON HIGH POWER! Use the fine adjustment to focus. Make a sketch of the letter under high
power on your paper, labeled: Letter – High power.
Letter-Low power
Letter-High power
Preparing slides- onion cells
1.
To make a wet-mount slide, get a microscope
slide and piece of onion skin. Add one drop of iodine
solution. IODINE WILL STAIN!
2.
Sit a coverslip at a 450 angle like shown in the
picture and drop it carefully over the liquid. DO NOT
PRESS DOWN ON THE COVER SLIP OR IT WILL BREAK!
3.
Place the slide on the stage under low power (yellow). You are looking for onion cells that look like
light yellow bricks. They are easier to see if you adjust the diaphragm to dim the light. Once they are focused,
draw them under low power, labeled: Onion – Low power
4.
Without moving anything, carefully switch to the high power objective (blue). DO NOT USE THE
COARSE ADJUSTMENT ONCE YOU ARE ON HIGH POWER! Draw a few cells under high power,
labeled: Onion – High power. Carefully clean off your slide.
Onion-Low power
Onion-High Power
Pond water
1.
Get a drop of pond water with some sediment on your slide. Carefully place the cover slip on top. Place
the slide on the stage under scanning power (red) and begin by looking for anything moving. You can switch to
low power (yellow) but don't use high power with the pond water.
2.
Carefully clean and return your slide and cover slip. Make sure your microscope is back on low power.
Unplug and cover it. Answer the analysis questions on your paper.
Analysis
1. What did you notice happened to the orientation (which way it was facing) of your newspaper letter when
you saw it on the slide compared to looking at it under the microscope?
2. Which power allows you to see with the most magnification and detail?
3. With which power should you never use the coarse adjustment to focus?
4. What was the most difficult step to complete while using microscopes?
5. What was the purpose of the iodine on the onion slide?
6. Describe what you saw in the pond water. Why do you think we only used low power?