Name__________________________________ Class _____ Date________
Biology Lab 1: The Microscope
Introduction
Most of cellular biology concerns objects that must be viewed with the aid of a microscope. It is
important to be able to use a student microscope fluently in order to successfully see cells and their
subcellular parts. The following parts are found on your microscope:
1. ocular lens - the eyepiece, 10X magnification
2. arm - supports scope and provides grip for carrying.
3,8. coarse and fine adjustment - allow for body tube or stage movement
and focusing an image for viewing
4,6,7. power cord, switch, and light – for illuminating the objects on the
stage
5. base - provided steady support.
9. condenser - concentrates or diffuses light before it passes through stage
opening. Settings range from 1 to 5.
10,11,12. stage, slide+coverslip, and stage clips - platform for slide; has
stage clips for holding a slide in position; has a stage opening in the
middle for allowing light to pass through a slide.
13,14,15. Low, high, medium power objectives - lenses mounted to
revolving nosepiece and located above slide; lens powers usually are
4X (low), 10X (medium), 40X (high)
16. revolving nosepiece - holds the objective lenses in position.
17. body tube - connects ocular to objective lens.
Terminology
1. slide = a small piece of glass onto which objects are placed for microscope viewing.
2. coverslips = small square pieces of plastic that are placed over an object on a slide to flatten it and protect the
objective lenses.
3. prepared slides = a premounted slide, often called "dry mounts" because a specimen has already been fixed on the
slide and preserved.
4. wet mounts = slide prepared by placing a drop of water on a slide, placing the object in the water (unless the water
contains the specimen), and carefully placing a coverslip over both.
SPECIAL NOTES:
1. When using your microscope, nothing should touch the scope lenses (including your fingers) except the
special lens paper that is made specifically for lens cleaning!
2. When focusing with high power, always look to the side while raising the stage to avoid contacting the
coverslip with the high power objective! NEVER TURN THE COARSE FOCUS KNOB WHEN
LOOKING THROUGH THE HIGH POWER LENS! THE LENS COULD BE DAMAGED!
3. To find total magnification, the powers of the lenses must be multiplied!
4. When putting a microscope away, turn off the light, unplug and wrap the cord around the scope base,
cover it, and put it in a secure area away from the table/countertop edge.
Procedure:
A. Simple Microscope Characteristics
1. Obtain a microscope and plug in the power cord. Turn on the light switch to on. Do not bump the
microscope while the light is on to prevent the bulb filament from breaking.
2. Look at the stage. It should be clean and dry. It should NEVER HAVE WATER OR ANY OTHER
SOLVENT/SALT ON IT. If it is wet, tell your instructor and then wipe it clean with a soft paper
towel.
3. Rotate the nosepiece and note that it locks in place when the lens is in viewing position. Find the
condenser and determine which settings allow most light and which allow least light by rotating it
while looking through the ocular.
4. Rotate the nosepiece to low power and turn the coarse focus. Note which moves, the body tube or the
stage.
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Name__________________________________ Class _____ Date________
Biology Lab 1: The Microscope
B. Basic Characteristics of Microscope viewing: lens, focus, and condenser.
1. Prepare a wet mount of a lower case "e". Put it on the stage and position the “e” over the stage
opening.
2. Locate the letter under low power first, and note the orientation of the letter with respect to its position
on the stage.
3. Adjust the condenser through all 5 positions to find the best view.
4. Move the slide in several directions while viewing the letter under the scope and note the directions in
which it appears to move.
5. View the letter under medium and high powers and try adjusting both coarse and fine focus for a clear
image. Under high power, move the condenser through all 5 adjustments to find the clearest image.
C. Depths of Focus
1. Prepare a wet mount of crossed threads or hairs of different color (any 2 different colors). Put the slide
on the stage so that the area where the threads cross is over the stage opening.
2. Locate the exact position where the threads cross under LOW power. Focus up and down with the
coarse focus and determine whether both threads are in focus at the same time.
3. Then, switch to MEDIUM power and again focus the coarse focus to determine if both threads are in
clear focus at the same time.
4. Lastly, switch to high power and adjust the FINE focus to determine if both threads are in clear focus at
the same time.
D. Estimating Microscope Sizes
1. Obtain a clear ruler (or a photocopy of one) with millimeter markings.
2. Place the ruler on the stage and bring some millimeter markings into focus under low power.
3. Position the ruler so that one marking is at the left edge of the field of view.
4. Count the millimeter markings able to be viewed (estimate partial increments) and record this number
as low power field size. Record the number.
5. Repeat this procedure to find the field diameter under medium power. Record this number.
6. Switch to high power and repeat the procedure, noting that the field diameter is less than one
millimeter. You must thus estimate the field diameter of high power by moving the ruler back and
forth to determine an approximate measurement. Record the number.
E. Observation of a prepared slide.
1. Obtain a prepared slide of some type of protist/algae/animal provided by your instructor. This is a
prepared slide, DO NOT PUT WATER ON IT!
2. Put the slide on the stage so that its coverslip is directly over the stage opening. View the organism
under low power first, focusing as clearly as possible on the cells. Draw the organism as detailed as
you can in the circle below marked "low power".
3. Switch to medium power and again focus clearly on the organism cells. Draw the algae as detailed as
you can in the circle below marked "medium power".
4. Switch to high power and again focus clearly on the organism. Again draw the organism cells as
detailed as you can in the circle below marked "high power". Label the object on each circle that you
think is a cell.
5. Show the width of one cell (strand) on each drawing. Make sure it is clearly labeled.
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Name__________________________________ Class _____ Date________
Biology Lab 1: The Microscope
Observations
Part A (general characteristics)
condenser settings: _____ = hi light, _____ = low light
other notes:
Part B (optics)
letter “e” orientation (arrangement and position on the stage)
letter “e” movements on stage compared to its apparent movement through lenses:
Part C (layers of focus)
low power:
Part D (field diameter)
low power (X40) FD:
medium power:
high power:
medium power (X100) FD:
high power (X400) FD:
Part E
low power
medium power
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high power
Name__________________________________ Class _____ Date________
Biology Lab 1: The Microscope
Questions
1. How do the optics of the microscope affect the orientation of viewed microscopic objects?
(besides making them look bigger!)
2. How is total magnification computed? If the eyepiece is 10X and the objective is 30X, what
is the total magnification?
3. What is the important purpose of a coverslip?
4. Why must you always look to the side when using coarse focus and the 40X objective?
5. What is the relationship between increasing the magnification and the depth of focus?
6. When a very small object is placed on a microscope stage for viewing, under what power
should it be viewed first, and why?
7. On each of the views below, estimate the length of the cell (marked length). Use a ruler and
SHOW YOUR WORK! Use the field diameters measured in lab. To calculate the lengths,
divide the drawn length of each organism by the drawing circle diameter, and multiply this
by the actual field diameter.
size of the Amoeba:
size of the plant leaf cell:
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size of the bacteria: