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The
Microscope, a Close-up Look for the Amateur
Master
Teacher: Jeff Duffy
Grade Level: 5-8
Time Allotment: 1-2
fifty-minute class sessions
Overview: Students
will make a microscope from a drop of water, then learn the basic parts and
functions of a compound microscope. They will observe fresh cells by preparing a
wet mount slide and learn the proper technique for setting up and using a
compound light microscope. Additionally they will calculate magnification and
field of view. Finally, they will
learn where to find information about objects that are not readily available in
the classroom to observe.
Subject Matter:
Science, Math
Learning Objectives:
The student will be able to:
ź
Demonstrate
a working knowledge of the vocabulary associated with the preparation of wet
mount slides and proper setup and use of a compound light microscope,
ź
Set up a
compound light microscope and make the necessary adjustments to accurately
describe the viewed item, and
ź
Calculate
the field of view, total magnification, and estimate the size of a viewed item.
Standards:
From the
National Science Education Standards, Grades 5-8:
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Develop
abilities necessary to do scientific inquiry,
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Use
appropriate tools and techniques to gather, analyze and interpret data,
ź
Use
mathematics in all aspects of scientific inquiry,
ź
Develop an
understanding of the structure and function in living systems, and
ź
Appreciate
that all organisms are composed of cells.
Media Components:
Video
Simply Science: Lab Skills Training and Review #125
Materials:
Compound microscopes: one per student ideal, one per three students acceptable
ź
Microscope
slides: at least one per student
ź
Cover slips:
at least one per slide
ź
Razor blade,
scalpel or knife: one, for the teacher only
ź
Paper towels
or bibulous paper
ź
Iodine and
dropper
ź
Small metric
rulers: one per student ideal, one per three students acceptable
ź
Beaker of
clear water and a dropper for each student
Prep for Teachers:
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Visit the
Internet or the library to examine the history of the compound light microscope.
ź
Be certain
that all microscopes are in good working order and those lenses are clean.
ź
Cue the tape
to the section titled “Microscope Skills”.
ź
Have small
patches of fabric, small print objects or other items with very fine detail
available for viewing with the “water drop” microscope. (Described in
“Introductory Activity”).
Introductory Activity:
Step 1:
Provide each student with a small piece of fabric, hair, or fine print and have
them observe with their unassisted eyes and then describe it.
Step 2: Have
them cover the object with a clean glass slide, then observe and describe it
again.
Step 3:
Finally, place a small drop of water on the slide. Have the students look
through the drop and describe what has happened to the image. (The curvature of
the water drop magnifies the image, forming a simple microscope.)
Step 4:
Encourage the students to try layering two slides to form a compound microscope.
Use the notion of magnifying a magnified image to begin viewing the video Simply
Science: Lab Skills Training and Review.
Learning activities:
Step 1: Tell the students that for hundreds of years, scientists have been using
microscopes to observe all types of objects. One of its most powerful
applications is in the area of life science, where it is arguably the most
important piece of technology.
Step 2: Start
tape where title “Microscope Skills” appears.
Pause:
Title “Compound Light Microscope” appears. Focus
for Media Interaction Ask students what this means. (A microscope of more
than one lens and powered by some form of visible light) Answers will vary.
Step 3: Play:
The supplies needed to prepare a wet mount slide are listed, followed by the
procedure.
Pause: Focus
The cover slip is tapped gently and the narrator says, “OK”. Have the
students duplicate this activity. Before further viewing, ask, “What do you
think she will see”? Listen to responses, then say. “Let’s find out.”
Step 4: Play:
Little is seen so iodine is applied to the specimen. Ask why the tissue was
applied to the point away from where the iodine was introduced. (To draw the
iodine across the specimen) Say, “Let’s find out what she saw after staining
with iodine.
Step 5: Play:
The procedures for placing a wet mount slide on the stage, and then focusing the
microscope are given.
Pause: She
says, “There you can see your wet mount” and a microscope image appears.
Step 6: Rewind
and Pause: The slide is placed under the stage clips Focus:
Say, “Let’s watch this again before we try it ourselves.”
Play: The
students will view the same segment again to emphasize the basic steps for
focusing. (Start on low power with the objective lens as close as possible to
the object). Note: Some microscopes may differ than those in the video in that
the stage may be fixed and the body tube moves.
Pause: She
says, “Now you can see your wet mount” and the slide view switches to a
close up of a nosepiece. Students should place previously prepared, unstained
potato smear on the stage and observe on low power. After all have succeeded in
viewing on low power, ask if a more detailed view may be made. (yes, on high
power) Focus Say, “Let’s see how
this is done.”
Step 7: Play:
This segment explains how a high power observation is made.
Pause: She
says, “There we have it” and a magnified image slides to the side of the
screen. Have the students follow the video demonstration and view their wet
mount slide on high power. Note: The distance between the slide and the high
power objective in the video is atypically great. Use only the fine adjustment
knob when on high power. After high power observations have been made, have
students compare those observations with low ones. Some should note that there
is greater detail on high power but a smaller area is seen.
Focus: Ask “How do you determine how much area you are viewing. Let’s
take a look.”
Step 8: Play:
A technique for measuring the field of view and calculating the powers of
magnification is shown.
Stop: She
says, “gives us a window into the world that can’t be seen with the naked
eye” and she looks over her shoulder at the microscope.
Step 9: Have
the students use rulers to determine the field of view of their microscopes or
brainstorm on other way that that task might be accomplished. Step 10: Calculate
the power of magnification for the different lens combinations.
Culminating activity:
Have the students prepare wet mount slides of various items from the classroom.
Cheek cells or scrapings from teeth are great. Diatomaceous earth, root hairs,
leaf epidermis, very small insects, or a drop or two of pond water are also
great to observe.
Cross-Curricular
Extensions:
COMPUTER
SCIENCE
Students may research different types of microscopes using the Internet. They
may also find sites that allow them to practice “techniques” using virtual
microscopes.
MATH
Students can calculate/estimate the real size of organisms viewed with the
microscope.
ART
Produce detailed drawings of objects viewed using the microscope.
SOCIAL
STUDIES
An explanation of the importance of the microscope and disease can be detailed.
Community Connections:
Students may visit a hospital, medical lab, or veterinary clinic to view the
microscope “at work.” Visit an observatory or optometrist to see other
applications for lenses.
Student Materials:
none
Updated: April 01, 2008
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