Microscopy and the Metric
The compound light microscope effectively magnifies in the range of 40x to 2000x. If an object under view is 10 nm in length without any magnification, what will be its viewing size at 40x?
at 2000x?
What is the equivalent size at these magnifications, in inches? Show your calculations.
The scanning electron microscope (SEM) employs electron bombardment to image very small specimens. Electron microscopes are used to image specimens that range from 1 nm to 100 µm in size. What is the equivalent in inches? Show your calculations
Microscopy and the
Metric System
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Lab Report Assistant
This document is not meant to be a substitute for a formal laboratory
report. The Lab Report Assistant is simply a summary of the
experiment ’s questions, diagrams if needed, and data tables that
should be addressed in a formal lab report. The intent is to facilitate
students’ writing of lab reports by providing this information in an
editable file which can be sent to an instructor.
Obser vations
Data Table 1: Calculating Magnification
Ocular Lens Magnification
x
Data Table 2: Diameter of a Viewing Field
Scanning Lens
Low Power Lens
High Power Lens
Exercise 1: Measuring Length, Weight, Volume, and
Temperature
Try the following conversions for practice.
240,000 ng =
mg =
g
50 cm =
mm =
m
Procedure
1. Length: A metric ruler is useful for measuring items of length. The ruler below measures in
mm, indicated by the small mm near 0.
a. How many mm are there in 1 cm?
, in a meter (m)?
(Ruler is not to scale. See ruler in dissection kit.)
b. Locate a measurable object to use for this exercise. If the object is long, obtain a yardstick
that includes a cm scale; they can be found in local hardware stores.
c. Record the length of the object below and do the conversions:
Name of object
Volume: Always pour an approximate volume of liquid into a clean beaker and then from the
beaker into the volumetric flask or graduated cylinder. This will minimize contamination of the
parent liquid source. Dispose properly of any leftover liquid. Do NOT pour it back into the
original container. Why?
When using a pipet or dropper to measure liquid, pour an aliquot into a clean beaker and then
draw up the liquid from the beaker into the pipet. NEVER try to draw up chemicals by mouth.
Why?
Weight: Use the pen scale from the lab kit to measure out exactly three grams of sugar. Make
sure to tare the bag before adding the sugar. Why must the bag be tared before adding the sugar?
How is the weight of the bag accounted for when the sugar is weighed?
Temperature
:
Practice converting the following with this conversion formula:
45°F =
°C
°C
62°F =
45°F =
98.6°F =
°C
98.6°F =
62°F =
Use a Celsius thermometer to measure the °C temperature of several different aliquots of cold
and warm tap water. Make sure to allow the thermometer to remain until the temperature is stable
and no longer changes. Record the temperatures:
°C
°C
°C
Questions
A. What laboratory equipment would be used to measure the following items?
5 g flour
The length of a frog ’s leg
38ºC
125ºF
Weight of a plant
Temperature of a fish’s body
*This answer may require some creativity. How could it be done?
B. Provide the calculation steps, including the conversion factor that would be needed to convert
the following measurements, and the final answers. Use U.S. and liquid units where appropriate.
248 g
536 mL
0.75 L
C. Provide the calculation steps, including the conversion factor that would be needed to convert
the following measurements, and the final answers. Use US and liquid units where appropriate.
3 cups
=
L
7,893 mg =
lb
2.25 oz
=
cc
36ºC
=
ºF
96ºF
=
ºC
145,000 uL =
tsp
D. What advantages does the metric system have over the English method of measurement?
What are the disadvantages?
E. Outline the steps necessary to accurately weigh 3.5 g of starch.
F. Outline the steps necessary to accurately pipet 5 mL of distilled water. Pour an aliquot of
distilled water into a clean beaker.
Exercise
Microscopy
2:
The compound light microscope effectively magnifies in the range of 40x to 2000x. If an
object under view is 10 nm in length without any magnification, what will be its viewing size at
40x?
at 2000x?
What is the equivalent size at these magnifications, in inches? Show your calculations.
The scanning electron microscope (SEM) employs electron bombardment to image very small
specimens. Electron microscopes are used to image specimens that range from 1 nm to 100 µm in
size. What is the equivalent in inches?
. Show your calculations.
Procedure
1. Parts of the Compound Light Microscope: Refer to a microscope as this section is read.
Label the microscope diagram that follows as the examination of the microscope proceeds.
a. What is the powerLens): The magnificaMicroscopess mtay haveonnthechangeable tocular
Eyepiece (Ocular of the ocular lens? tion power i s amped i ter outside of he lens.
lenses of different magnification.
b. Body Tube: Holds the ocular and objective lenses at the correct focal distance.
c. Arm: Used to transport microscope and hold the body tube.
d. Nosepiece: The revolving device that holds the objective lenses. May also be referred to
as the turret.
e. Objective Lenses: Consists of one or more lenses:
i. The scanning power objective lens is the shortest of the lenses. What is its power?
ii. The low-power objective is slightly longer than the scanning objective. What is its
power?
iii. The high-power objective is longer than the low-power objective. What is its power?
Label this microscope diagram with the appropriate part names and their functions:
a
b
c
d
e
f
g
h
i
Parts not included in microscope are:
2. Focusing the Microscope:
If the microscope includes an oil immersion lens, place a drop of immersion oil on the slide cover slip
before rotating the lens into place. The function of the oil is to minimize light diffraction through the
slide and subject so that greater detail can be seen. After using the oil immersion lens, clean excess oil
off of the lens and the slide with a lens cloth. Never tilt a microscope when using oil or if viewing a wet
slide. Why?
3. Operating the Microscope:
a. Obtain a clean slide and cover slip from the slide box. Place the slide and cover slip
separately on a paper towel or other soft surface to reduce the possibility of scratching
them.
b. With scissors, cut a letter “e” from an old magazine or newspaper.
c. Place the letter in the center of the slide.
d. Follow the instructions in Section 6 below to make a wet mount of the letter.
e. Following the directions outlined above under Handling and Focusing the Microscope,
place the prepared slide on the microscope stage. Leave the scanning lens in place and
focus so that the letter is clearly viewable. Make drawings of the letter in the boxes below
as instructed.
Side of the slide furthest away from student
Side of the slide closest to student
f. What is observed? Microscopes invert the image on the slide. This means that the subject
will appear to be 180° rotated and reversed from the actual image viewed on the slide.
g. While viewing the letter through the lenses, move the slide slightly. What do you observe
about the movement of the letter and slide when viewed through the lenses?
h. Use the directions above to view the letter at the higher objective powers. On the drawing
made above, circle the portion of the letter that is viewable as successively higher power
observations are made. What is your conclusion about what happens when higher power
objectives are used?
4. Total Magnification Calculation: Typically, the ocular lens of a microscope will be 10x,
but it may be higher or lower. The power is recorded on the side of the lens.
a. Rehot dsit he ocular 1. power of the microscope that you are using? It may be 10x or 15x.
Wc ar i t in Table lens
b. The objective lenses also have the magnification power recorded on their sides. What
powers do the objective lenses on the microscope have? Record them in Table 1.
c. Now, calculate the total magnification of the viewing area by multiplying the power of
the ocular lens with that of the objective lens in use. For instance, if a microscope has
a 10x magnification ocular lens and a 4x objective lens in place for viewing, the total
magnification will be 40x (10x multiplied by 4x). What other view magnifications are
possible with the microscope? Calculate the total magnification for each set of lenses in
Table 1.
Table 1: Calculating
Magnification
Ocular Lens Magnification x
5. Diameter of Field:
a. With the low-power objective in viewing position, place a short transparent metric ruler
on the stage.
b. While viewing the ruler through the lenses, measure the low-power diameter of field of
view in mm. Convert this measurement to ?m and record in Table 2.
c. 2.witonvtertthe easurements po wer oHow ves,htoting itnformation r, en usefulfor hen viin wing
S C ch o m other higher t o ?m. bjectimig n this he diamete bi mm, w each e Table
microscopic subjects?
Table 2: Diameter of a Viewing Field
Scanning Lens
Low Power Lens
High Power Lens
6. Depth of Field: Prepare a wet mount slide of three differently colored crossed threads using
the wet-mount technique described above. Place the slide on the microscope stage with the
thread crossing area in the center of the viewing area. Focus carefully, moving the scanning
objective lens up and down, taking care not to break the cover slip.
Record the order of the threads in this table. Note that, when one thread is in focus, the others
appear blurred. Why? When you focus on another thread, what happens to the thread that you
were viewing?
Depth
Top
Middle
Bottom
Switch to high power and focus on one thread, then focus on another thread. What do you
notice about the depth of field? Can you see as much of the thread in focus at the high power
as you could at the low power magnification?
7. View an animal cell:
a.
Observe the prepared slide under the microscope, beginning with the scanning lens and
then proceeding to higher magnification levels. Locate the nucleus in several cells. Locate
the cytoplasm and the plasma membrane. On a sheet of paper, make a drawing of a few
cells, and label the observed parts.
8. View a plant cell:
a. Observe the slide under the microscope, beginning with the scanning lens and
then proceeding to higher magnification levels. Locate the cell wall and the
nucleus in several cells. Make a drawing of a few cells and label the observed parts.
b. Count a column of cells, stacked end-to-end, across the field of vision under high-power
magnification.
c. F. Based on the field of vision measurement you calculated above, compute the average
length of one cell in the column of cells with this formula:
?m average length of cell = ?m diameter of field of view ÷ total number of cells in the column.
d. What differences were noted between the animal cells and the plant cells?
e. How do the differences dictate the form of the organism?
Discussion
A. What is the purpose of staining cells before viewing them under a microscope?
B. What type of microscope would you use to view the following organisms? There may be
more than one correct response for each.
Strep throat culture
Structure of a bird feather
Earthworm digestive system
DNA structure in the nucleus
Cells from plant leaf
C. Summarize the capabilities of each of the microscopes listed in Table 2-3 below.
Table 3: Summary of Microscope Capabilities
Type of Microscope
Dissecting
Compound Light
Scanning electron
Transmission electron
Laborator y Summary
1. What have you learned from doing this laboratory?
2. Why is the information presented in this laboratory intrinsic to all future studies in biology?