In This Lesson:
Unit 2
Microscopes
(Lesson 1 of 5)
Today is Wednesday,
October 7th, 2015
Pre-Class:
Write down three facts you know about
microscopes. I will call on each of you for one of
them.
Please get a SMALL paper towel for your pair and
take a worksheet from the turn-in box.
Today’s Agenda
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Challenge Questions
Unit 2 Pre-Test
History of microscopes
Virtual microscopes
Real microscopes
Seeing atoms
Painting with fly hair
• Where is this in my book?
– Academic: P. 169 and following…
– Honors: P. 52 and following…
By the end of this lesson…
• You should be able to properly use a
microscope and describe its parts and their
functions.
• You should be able to distinguish between
types of microscopes, including their
advantages and disadvantages.
IMPORTANT NOTE
• Some of the information we need to learn
about microscopes will be discussed when we
do the Microscope Lab.
– If you’re absent that day, make sure you consult
the “Theoretical Data” file and the file called “Lab
– Microscope – Information” on my website
(Assignments section).
History of Microscopes
• In the beginning, around 1284, eyeglasses
were invented.
I still couldn’t see
the Bubonic
Plague coming.

http://www.spectaclesblog.com/wp-content/uploads/2009/09/spectacles-in-the-scriptorium-1352.bmp
History of Microscopes
• Around 1590, two Dutch
guys (Zacharias Janssen and
his son Hans Janssen) put a
bunch of lenses together in a
tube and noticed that they
brought small objects into
focus.
• Early light microscope!
– Janssen also claimed credit for
inventing the telescope, but
that usually goes to Hans
Lippershey.
http://micro.magnet.fsu.edu/optics/timeline/people/antiqueimages/lippershey.jpg
http://www.microscopy-uk.org.uk/mag/imgjan07/Fig004s.jpg http://www.history-of-the-microscope.org/images/Zacharias-Jansen.jpg
Light Microscopes
• Light microscopes, like the ones we’re using,
require light to pass through the sample and
into the eyepiece.
• Relatively inexpensive.
• Can see down to around the level of cell parts
– maybe a little smaller.
• Can use living things.
• Sometimes called optical microscopes.
Then a lot of time passed…
• Until we got to the early 1900s. The scanning
electron microscope was invented.
– Uses a beam of electrons to create images!
• It’s big, it’s bulky, it’s expensive, but it’s superpowerful. Does not allow for living specimens.
– Samples must sometimes be coated in gold!
• Does not require light to pass through an object.
• Can view objects about the size of the diameter
of an atom.
Types of Microscopes
• Scanning Electron Microscope:
http://img.directindustry.com/images_di/photo-g/schottky-emission-scanning-electron-microscope-sesem-237074.jpg
Electron Microscope Images
http://blog.lib.umn.edu/willow/bioarts/exhibition-ideas/
Electron Microscope Images
http://blog.lib.umn.edu/willow/bioarts/exhibition-ideas/
Electron Microscope Images
Trichinosis spiralis
(microscopic animal parasite from undercooked meat)
http://www.photosfan.com/electron-microscope/
Electron Microscope Images
http://www.photosfan.com/electron-microscope/
How “Far” Can They See?
• Let’s compare.
• Scale of the Universe
Scanning Tunneling Microscope
• Invented in 1981.
• Currently the most powerful microscope
available.
• Can see three-dimensional objects at the
atomic level.
• Video!
Willard Wigan
• And now for something a bit
more…unusual…having to do with
microscopes.
• This is real.
The Microscope Checklist
• So, let’s talk about the parts of a microscope.
• Head to your lab tables with your worksheets
and notebooks.
• Two people from each table should get
computers.
Parts of a Microscope
10. Eyepiece
9. High-Power Objective
1. Arm
4. Diaphragm/Iris
7. Low-Power
(Scanning) Objective
8. Mid-Power Objective
6. Stage Clips
5. Stage
11. Coarse Focus Knob
3. Light
12. Fine Focus Knob
2. Base
Parts of a Microscope
• Arm
– Supports the stage, eyepiece, and objectives.
• Base
– Supports the scope.
• Objectives and Eyepiece
– Magnify the sample.
• Stage and Stage Clips
– Hold the slide.
Parts of a Microscope
• Coarse Focus
– Focuses the image on low power.
• Fine Focus
– Focuses the image on higher powers.
• Diaphragm/Iris
– Controls the amount of light entering the
objective.
• Light
– Provides the uh…light.
Meet Your Microscope
• Follow this path on your microscope:
– When using a light microscope, light comes up
from the source through the diaphragm.
– It passes through the slide and the object
mounted on the slide.
– It goes into the objective lens, up the tube and
through the eyepiece lens, finally going into your
eye.
Handling Your Microscope
• First, only handle the scope by the base and
arm.
– One hand on the arm, the other underneath, as
though you’re carrying a giant teacup.
– See demonstration!
– Give it a shot yourself. Make sure everyone at
your table has an opportunity to pick up and set
down the scope.
Meet Your Microscope
• On low power, the light entering the objective is
magnified how many times?
– 4x
• However, it has to pass through another lens –
the eyepiece!
– The eyepiece magnifies 10x.
• Therefore, to find total magnification, multiply
eyepiece magnification by objective
magnification.
– What are the possible magnifications here?
– ALWAYS include magnification with any sketches you
draw. It’s like including units with measurements.
Virtual Microscope
• Now we’re going to do a little practice on a virtual
microscope.
• First, log into Quia and complete the Unit 2 PreTest as a pair.
• When you’re finished, launch the following
website:
– Virtual Microscope
http://www.udel.edu/biology/ketcham/microscope/sc
ope.html
• Close the tour and turn on the checklist.
• View the letter “e” on the microscope correctly,
then call me over.
Virtual Microscope
• http://www.udel.edu/biology/ketcham/microscope/scop
e.html
– Or Supporting Documents – called “Virtual
Microscope.”
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Close the tour.
Select the slide with the “Letter e” mounted on it.
Select “Checklist” from the upper left corner.
Complete each of the steps. You will need to
figure out how to do some of this on your own.
– Consider it a scavenger hunt!
• When you are finished, show me your results,
turn off your computer, and put it away.
Closure
• Using a whiteboard, answer the following
questions:
– Rank the microscopes in terms of increasing
magnification power:
• Light Microscope, SEM, STM
– What is the total magnification on your highpower objective? How did you calculate it?
• (show the equation)
Closure
• TED: Dee Breger – Visualizing Hidden Worlds
Inside Your Body