HONORS LIVING ENVIRONMENT
MS. ETRI
TOPIC 2: LAB TOOLS AND LAB SKILLS
PART 3: MICROSCOPE USAGE AND OTHER LAB SKILLS
LIGHT MICROSCOPES
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________________________________________________________________________________
Send light through a path that first focuses the light into a light beam and then passes light through a
sample, which creates an image.
TWO TYPES
1. ________________________________________________


Use a ___________________ lens to magnify an object
Cannot reach high magnification
2. ________________________________________________
 Allows light to pass through an image
o As a result, the specimen must be very small or very thin.

Uses _______________________________ to magnify an object

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Monocular microscopes have one eyepiece
Binocular microscopes have two eyepieces
(reduces eye strain)
PAPER MICROSCOPES?!
https://www.ted.com/talks/manu_prakash_a_50_cent_micr
oscope_that_folds_like_origami?language=en
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PARTS OF THE MICROSCOPE
HOW TO HANDLE A MICROSCOPE

Hold the microscope with one hand around the ____________________ of the device, and the other
hand under the _______________________.

Do not touch the lenses of the microscope. Oil and dirt from your fingers can scratch the glass.

Clean smudges on the microscope glass with ________________________. Or, ask your teacher to
clean the lenses for you.
o
Any other material (such as tissues) can scratch the glass of the microscope.
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Never use coarse adjustment on high power! It will move the stage up and scratch the lens.
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When finished using the microscope, rotate the nosepiece to ___________________________ and
turn the stage down to its lowest setting.

Cover the microscope with the _______________________ to protect it from dirt and debris.

Turn off light source when not in use.

Clean slides when finished.
TOTAL MAGNIFICATION
 When you are seeing an object through the eyepieces of a compound microscope, the image that you
are actually seeing is magnified twice: by the _________________________ AND the
_________________________________ you are using to view an object.
TOTAL MAGNIFICATION = _____________________________________________

We can see better detail with higher powers of magnification, but we cannot see as much of the image.
CALCULATING TOTAL MAGNIFICATION (COMPOUND LIGHT MICROSCOPE)
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Scanning (red)
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Eyepiece/Ocular Lens
Objective Lens
10X
4X
Low Power (yellow)
High Power (blue)
Total Magnification
100X
40X
NOTE: The magnification power of the eyepiece is usually 10X.
FIELD OF VIEW

_______________________________________________________________________________

***As _____________________________ increases, the _________________________ decreases.***

The size of a microscopic field of view can be determined on low power using a device called an optical
micrometer. An economy version of this can be made by placing a clear metric ruler on the stage of a
microscope and using it to estimate the field of view.

The light microscope is used to look at cells or other similarly sized microscopic objects, so small units
of measure such as ________________________________________ are used.

Remember: 1 millimeter = __________________ micrometers.
___________________ millimeters = 1 meter
HOW DO SPECIMENS APPEAR WHEN THEY ARE VIEWED UNDER A MICROSCOPE?
_______________________________________________________________________
WHEN YOU MOVE THE SLIDE LEFT, WHICH WAY DOES THE IMAGE APPEAR TO MOVE?
_______________________________________________________________________
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*If you move an image to the right, when you look through the microscope, it will appear to be moving left!
CALCULATIONS INVOLVING FIELD OF VIEW
1. FINDING THE SIZE OF A MICROSCOPE FIELD OF VIEW
 REMEMBER: When given a ruler, the black lines represent the measurement markings. You
should count the spaces in between the black lines for your entire FOV to obtain an accurate
measurement.
 How many millimeters is the microscope field of view?
_______________________________

How many micrometers if the microscope field of view?
______________________________.
2. FINDING THE SIZE OF MULTIPLE CELLS IN A FIELD OF VIEW

How many millimeters is each cell? ________________________

How many micrometers is each cell? _______________________
3. ESTIMATING CELL SIZE WHEN THE FIELD OF VIEW IS KNOWN

Approximately what fraction of the FOV does the ameba take up?
________________________
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If the field of view on the left image is 3mm, approximately how large is the ameba in the image?
In mm:
In um:
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The student is now viewing the ameba under high power (40X).
The specimen appears 4x larger than it was under low power
(10X)
The specimen appears larger because the field of view
decreased.
PREPARATION OF A WET MOUNT
1. Obtain a clean microscope slide and a coverslip.
a. A __________________________ is very thin, permitting the objective lens to be lowered
very close to the specimen.
2. Place the specimen in the middle of the slide.
3. Using a ___________________________________, place ONE
drop of water on the specimen.

Don’t use too much or the water will run off the edge
and made a mess!
4. Place the edge of the coverslip on one side of the water drop at a
_____________________________________
5. Slowly lower the coverslip on top of the drop of water.

Try not to trap any air bubbles under the coverslip. If air bubbles are present, gently tap
the surface of the coverslip over the air bubble with
a pencil eraser.
6. Remove any excess water at the edge of the coverslip with a
paper towel.

If the specimen begins to dry out, add a drop of
water at the edge of the coverslip.
7. Place the slide on the stage and view it first with the red-banded
objective. Once you see the image, you can rotate the nosepiece to view the slide with the different
objectives.
STAINING
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________________________________________________________________________________
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________________________________________________________________________________.
Common stains: Lugol’s iodine and Methylene blue
o Methylene blue is often used to
stain animal cells to make the
nuclei more observable.
Place a drop of stain at the edge of the coverslip.
Place the towel on the opposite side of the coverslip.
o This will draw the stain through
the entire specimen without
moving the coverslip.
INDICATORS

Chemical compounds used to detect the presence of other compounds or to test if a substance is an
acid or base.
COMMON INDICATORS
1. Litmus Paper: determines whether solutions are
______________________________ (doesn’t provide the actual pH).
o
Turns _____________ in acids, ________________ in bases.
2. pH Paper: determines the actual pH number.
o
When dipped in solution, paper turns different shades of various
colors.
o
Paper is then compared to a scale to determine the _______________________________.
3.
Bromothymol
Blue
o
Turns from _______________ to ___________________ when carbon dioxide is present.
o
Used to indicate respiratory activity (turns yellow as carbon dioxide is released).
4. Lugol’s Iodine/Solution
o
Brown solution that turns ____________________________ in the presence of starch.
5. Benedict’s Solution
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o
Detects the presence of simple sugars (glucose).
o
Must be heated for a short period of time.
o
Turns from blue to orange-red/brick red when glucose is present.
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