Microscope Lab
Biology
Mr. Banerjee
Microscope Lab
This lab will have you in teams. Each team must submit a lab write up. The lab write up for this
activity will be handwritten and in a duo tang. One person will need to read the directions at a lab
station while the other manipulates the microscope. It is essential that all team members become
familiar with the appropriate and efficient use of the compound light microscope so make sure
all of you use the microscope as instructed.
The most widely used scientific instrument in Biology is the Microscope. Without the
microscope, an understanding of the basic nature of life would not be possible. There are several
types of microscopes. Some use light to establish an image of a subject and others use electrons.
We will be using compound light microscopes to look at subjects that are 5mm or smaller. We
will use stereo microscopes (dissecting microscopes) to look at specimens larger than 5mm.
The compound light microscopes we will be using have three objective lenses. The shortest has a
magnification of 4x (scanning power), the middle sized one has a magnification of 10x (low
power), and the largest is 40x (high power). Look at the number on the lens to determine which
you have.
Materials:
compound light microscope
stereo microscope
lens paper
microscope slide
microscope cover slip
slide with the letter e (Students prepare)
slide with crossed threads (Students prepare)
slide with yeast organism (Students prepare)
(Prepared slides are expensive and very
delicate - be very carefully not to drop these
slides: you drop it...... you buy it!)
Yeast Preparation:
Yeasts are unicellular fungi that are used to make alcoholic beverages such as wine and beer, and
also in baking. They consume sugars and, through the process of fermentation, produce alcohol
and carbon dioxide.
Materials:

Compound microscope

1 cup warm water

One packet of active yeast

Microscope slides and cover slips

Dropper or pipette

1 tablespoon of sugar
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Microscope Lab
Biology
Mr. Banerjee
Instructions:
To begin, you need to prepare a yeast solution. Add the yeast and sugar to the warm water. Stir
and let it sit for 45 minutes. Once the yeast solution is ready, place a small drop onto a slide and
cover with a coverslip. Observe the yeast cells under high power. You may see some cells in the
process of reproducing. In yeast, this is known as budding.
Procedure Part A:
It is essential that you clean up your lab station thoroughly at the completion of the lab activity.
The cord of your microscope must be wrapped around the base (for storage and to avoid tripping
over cord) of the microscope and the plastic bag placed back over top (to keep dust from settling
on the lenses) when done. When moving the microscope to a new location ALWAYS hold one
hand under the base and the other should be firmly grasping the arm. You drop the microscope....
you bought it!!!
Using the diagram below become familiar with ALL THE PARTS OF THE MICROSCOPE and
be able to discuss their functions.(Knowing the functions of the parts of a microscope will be
essential for successful usage of the scope and performance on an upcoming test)
1. Ocular Lens (eye piece) - magnifies image
2. Nose Piece (turret) - allows user to rotate preferred objective lens into position
3. Objective Lenses - allows user to have multiple levels of magnification
4. Stage - specimen to be observed is placed on here
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Microscope Lab
Biology
Mr. Banerjee
5. Diaphragm - regulates amount of light passing through stage
6. Light Source - if you can't figure out the function of this you should not be in this class
7. Arm - one hand needs to firmly grasp this when moving a microscope
8. Stage Clips - these hold the slide in place on the stage (we will rarely use these)
9. Coarse Adjustment - used to move the stage up or down in large increments
10. Fine Adjustment - used to move the stage up or down in extremely small increments (fine
focus)
11. Light Switch 12. Base - one hand needs to be under this when moving microscope
Questions:
1- If total magnification is determined by Multiplying the ocular lens magnification by the
objective lens magnification, what three different levels of magnification can be achieved by
your microscope?
2- The thickness and transparency of the specimen being viewed under the microscope can vary
dramatically (ie: fly wing, dark green leaf).
A) What microscope part, which should be adjusted every time a specimen is placed on the
stage, would you use to establish ideal illumination?
B) Which setting might you use for the fly wing?
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Microscope Lab
Biology
Mr. Banerjee
Procedure Part B:

Place the microscope so that the arm faces you and the base is approximately 5cm from
the edge of the lab bench.

Clean the eyepiece and the objective lenses with lens paper only. Never use paper towels
or your shirt both of which may scratch the lens. Use a gentle circular motion when
cleaning a lens.

Plug in the microscope and turn on the light.

Open the diaphragm to the largest opening directly beneath the opening in the stage.

Turn the nosepiece so that the scanning power objective lens (smallest objective lens)
clicks into place directly above the opening in the stage. You will always start with
scanning power to locate the specimen before changing to higher magnifications.

Use the coarse adjustment knob and lower the stage as far as it will go.

Locate the slide with the letter e on it and place it on the stage SO THAT IT IS RIGHT
SIDE UP AND APPEARS EXACTLY AS YOU WOULD EXPECT TO READ IT!.
Move the slide so that the letter e is as close to the middle of the opening in the stage as
possible. DO NOT USE THE STAGE CLIPS. Most of our work will require moving the
slide on the stage and the clips tend to become more of an inconvenience than help.

Use the coarse adjustment knob and raise the stage as close to the lens as is possible.

Use the fine adjustment knob (moving the stage away from the lens) to get the letter e
CLEARLY FOCUSED (not blurry at all).
Questions:
3- While looking at the letter e through your microscope, gently move the slide to your left and
right and then up and down. A) What happen to the image when you move the slide to the right?
B)What happens to the image when you move the slide up?
4- Pay close attention to the orientation of the letter e while observing it through the microscope
at scanning power (40x). Using the plastic cup provided trace a small circle on your lab write up
and make a simple drawing of the letter e's orientation (how it now looks while under the
microscope).Accuracy is critical.
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Microscope Lab
Biology
Mr. Banerjee
Procedure Part C:




While looking at the letter e through your microscope gently move the slide so that the
letter e is as close to the center of the field of view as is possible.
Carefully rotate the nosepiece so that the Low Power Objective Lens (middle sized lens)
clicks into place directly above the opening in the stage.
While viewing the letter e pay close attention to how much of the field of view is
occupied by the letter.
Place the plastic ruler on the slide and look carefully at the number of millimeter lines
that can be seen in the field of view. The image below gives you an idea of how to
determine total diameter of the field of view.
1 mm = 1000 µm
Questions:
5- Knowing the diameter of the field of view at low magnification (100x) estimate the total width
of the letter e on your microscope slide.
6- Use the plastic cup to trace a small circle on your lab write up and in the circle draw the letter
e as it appears under your microscope at low power (100x)
Procedure Part D:

Remove the plastic ruler and move the slide so that the letter is exactly in the middle of
the field of view.

Lower the stage by turning the coarse adjustment one or two turns.

Rotate the High Power objective lens into position.

While looking at the stage from the side, use the coarse adjustment to move the stage so
that the lens is as close to the slide as is possible without touching it.
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Microscope Lab

Biology
Mr. Banerjee
Move your eye over the ocular lens and use the fine adjustment to focus the image.
Questions:
7- Use the plastic cup to trace a small circle on your lab write up and in the circle draw the letter
e as it appears under your microscope at high power (400x or 430x depending upon microscope)
8- Using the formula shown below estimate the diameter of the field of view at 400x
?
low power field of view
=
low power magnification
high power magnification
9- Why can't we simply place the ruler underneath the microscope at high power to determine
field of view?
Procedure Part E:

Rotate the nose piece so that the scanning power objective lens clicks
into place directly over the opening in the stage.

Prepare a slide with three different coloured threads & cover with a cover slip.

Place the slide with the crossed threads onto the stage.

Focus your microscope so that all three threads are clearly visible.

Move the slide so that where they cross over is in the middle of the field of view.

Carefully rotate the nose piece so that the low power (100x) is directly over the opening
in the stage

Move the slide so that you can observe where the three threads cross

Lower the stage by rotating the coarse adjustment one or two turns.

Rotate the High Power objective lens into position.

While looking at the stage from the side, use the coarse adjustment to move the stage so
that the lens is as close to the slide as is possible without touching it.
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Microscope Lab

Biology
Mr. Banerjee
Move your eye over the ocular lens and use the fine adjustment to focus on the area
where the three threads cross
Questions:
10- Use the plastic cup to trace circle on your lab write up and in the circle draw the crossed
threads as it appears under your microscope at high power (400x or 430x depending upon
microscope). Use the coloured pencils that are available to properly represent each of the three
threads.
11- Were all three colors clearly focused (all three equally clear at the same time) at scanning
power? Low power? High power?
12- Depth of field is the amount of vertical space in focus at a particular magnification. What
seems to happen to the depth of field as magnification increases?
13- Working distance is the space between the objective lens and the stage. What seems to
happen to working distance as magnification increases? Why should we lower the stage before
rotating the nose piece to high magnification?
14- What seems to happen to the diameter of the field of view as magnification increases?
15- Explain why it is important to move the specimen we want to view to the very middle of the
field of view before switching to a higher magnification.
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Microscope Lab
Biology
Mr. Banerjee
Procedure Part F:
Most specimens we will look at this year will require a "Wet Mount". This will involve using a
small square plastic cover slip to compress the specimen into a small a vertical space as possible
and create a tight seal so that it stays in place on the slide. The next procedure will take you
through the basics of how to make a wet mount preparation.

Acquire a single hair from either you or your partner.

Place the hair in the middle of a clean blank slide

Add two drops of water at the center of the slide where the hair lays across it.

Take the small square "Cover Slip" and let the edge of the slip rest on the slide and lean
at a 45 degree angle over the hair where the drops of water were added.

Allow the cover slip to fall, keeping the one edge in contact with the slide, over the hair
and form a tight seal with the two drops of water.

Turn the nosepiece so that the scanning power objective lens (smallest objective lens)
clicks into place directly above the opening in the stage. You will always start with
scanning power to locate the specimen before changing to higher magnifications.

Use the coarse adjustment knob and lower the stage as far as it will go.

Place the slide on the stage of your microscope attempting to position the area where the
hair is over the middle of the opening in the stage.

Use the coarse adjustment to focus.

Carefully view the hair under low power and high power as well.

Attempt to locate the numerous scales of protein that make up the human hair.
Questions:
16- Knowing the diameter of the field of view at different magnifications, what is the
approximate width of your hair?
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Microscope Lab
Biology
Mr. Banerjee
Procedure Part G:
You will prepare and observe cells from both a plant (onion) and an animal (your own cheek
cells!!).
Materials: You will need the following materials: glass slide, coverslip, toothpick, iodine stain,
onion tissue, and your own cheek cells.
Procedure:
17. use the plastic cup to trace circle on your lab write up and in the circle draw the prepared and
observed samplings of both types of cells as possible and sketch them.
You are also required, on your sketch, to label any visible parts or organelles, as well as list what
magnification you used. Lastly, you need to write down any other interesting observations
(difference between cells, cool things you saw, etc.).
For the onion cell:
1. Get a glass and place a small amount of onion tissue (peel a single layer) in the center.
Place a cover slip over the sample.
2. Add a small drop of water and follow the method for staining with iodine stain indirectly
to the tissue. Careful, Iodine is not toxic, but it will stain both you skin and your clothes.
3. Put the slide on the microscope, making sure the microscope is on LOW POWER!
4. Go through the three powers, focusing each time, making sketches, and writing down
observations. Be sure to write what magnification you used for each sketch.
5. Be sure to label any parts you see. You may be able to see: cell wall, nucleus, and
cytoplasm.
For the cheek cell:
1.
2.
3.
4.
5.
6.
Clean off your slide from above and add a drop of iodine to the empty slide.
Use the blunt (not sharp) end of the toothpick; gently scrape the inside of the cheek.
Swirl the toothpick end on the slide, now with cheek cells, in the iodine drop on the slide.
Place a coverslip on the stained cheek cells.
Observe under the microscope like you did for the onion cell above.
Record what you see in the field of view used and the magnification used.
Don’t forget to clean up!!
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Microscope Lab
Biology
Mr. Banerjee
Yeast cells observation.
Questions:
18- Use the plastic cup to trace a small circle on your lab write up and in the circle draw the
yeast cells as it appears under your microscope at high power (400x). Draw yeast cells that you
see ”budding”.
Procedure Part G:
It is essential that you clean up your lab station thoroughly at the completion of the lab activity.
The cord of your microscope must be wrapped around the base (for storage and to avoid tripping
over cord) of the microscope and the plastic bag placed back over top (to keep dust from settling
on the lenses) when done. When moving the microscope to a new location ALWAYS hold one
hand under the base and the other should be firmly grasping the arm. You drop the microscope....
you bought it!!!
Using the diagram below become familiar with ALL THE PARTS OF THE STEREO
(dissecting) MICROSCOPE and be able to discuss their functions.(Knowing the functions of the
parts of a microscope will be essential for successful usage of the scope and performance on an
upcoming test)
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Microscope Lab
Biology
Mr. Banerjee
The stereo microscope (aka: dissecting microscope) is used to look at objects too large to be
viewed under the compound light microscope (organs, entire organisms). The "stereo" ocular
lenses give the user a 3D view of the specimen.
First: Acquire a leaf from the back of the room (greenhouse), use your scissors to remove a leaf
from one of the many plant species from the greenhouse. Depending on the height of your
specimen you may need to raise or lower the microscope body to insure ideal focusing. Use the
height adjustment knob to set to the appropriate height if needed. Place the specimen on the stage
and then follow the procedures described below.
EYE SEPARATION: Different users may have eyes that are closer together or further apart.
The stereo microscope allows the user to adjust the distance of the ocular lenses by doing the
following:
1. Grab the left ocular with your left hand and the right ocular with your right hand as close
to the base of the scope as is possible
2. Rotate the two lenses in opposite directions or back together to adjust them to the ideal
separation for your eyes
EYE FOCAL LENGTH: There is a possibility that your right eye has a different focal length
than your left. To accommodate this possibility you have the ability to focus the left eye ocular
independently of the right eye. Follow the steps below to be sure you are able to look at the
specimen perfectly focused.
1.
2.
3.
4.
5.
6.
Place both eyes comfortably over the ocular lenses
Close your left eye and focus the scope for your right eye using the focus knob
Close your right eye and open your left.
Focus the scope for your left eye using the left eye adjustment (turn to the left or right)
Open both eyes and the specimen should be perfectly focused for both eyes
Each user may have to make minor adjustments to be sure the specimen is perfectly
focused both of their eyes.
ILLUMINATION: The switch on your stereo microscope allows you to illuminate your
specimen from above, from below, or from both sources. Very dense specimens might be best
illuminated from above only. Specimens with transparent regions may be best illuminated from
below. Other specimens may be best illuminated from both sources. It is very important that you
TRY ALL THREE to determine which is ideal for the specimen you are trying to observe.
1. The single master switch must be in the on position for any light to be provided
2. The pair of switches may both be in the off position and no light will be present
3. Try illuminating your specimen from above, below, and both by working with the pair of
switches on the opposite side of the stage as the master switch.
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Microscope Lab
Biology
Mr. Banerjee
MAGNIFICATION: Your stereo microscope has two levels of magnification. Rotating the
objective lens will change alternate magnification between 10X and 20X. While looking at your
specimen turn the objective lens clockwise until you feel it snap into place and notice the change
in magnification. Choose the most ideal magnification for the specimen that you have placed on
the stage and focus the scope so that the area of the specimen you are looking at is not blurry.
DRAWING:
19 - Use the larger diameter end of the plastic cup at your bench to draw a circle on your lab
answer sheet. Make a simple sketch of your specimen in the circle. AS ALWAYS, accurate
drawings are essential. If I cannot immediately tell what you have drawn you will receive no
credit. Extra credit mat be awarded for exceptional drawings.
20 - List three things that would be best viewed with the compound light microscope and three
things that would be best viewed with the stereo microscope.
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