Posted by
Barbara Foster on
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Hi, Mayandi
Optimizing Light Microscopy has tons of little experiments scattered
through it. We have a few copies (less than 10) left. Also,
don't forget Caroline Schooley's wonderful GEM progam. I'm sure
that there are a lot of things there. (Caroline
Schooley<
[hidden email]>)
Very there are three experiments which I strongly support:
a. Use of hand lens to differentiate between object and the image formed
by a lens. I have my students find the focal length by capturing
the image of the over head lights on the desk top. Once they know
the focal length, have them look through the lens at their fingernail at
the following distances: inside the focal length; then, holding
lens steady, move finger further out. At focal length finger will
disappear; beyond focal length it will reappear, but upside down.
You can tease them about "At no time did your finger leave your
hand!"
This expt is great for talking about the 4 General Cases of Lenses,
finding focal point, measuring focal length, On-axis versus off-axis
imaging, and focal plane)
b. For diffraction, you can actually just shine light past the edge of a
single-edge razor blade and image on the wall. Also, if you have
the kids VERY gently separate their fingers, hold their hands about
10" from their faces, and view a distant light source, they will see
Fraunhofer fringes between their fingers.
c. Then there is Pol... this is a real treat. I have a big
set of polars (I think you can get them from Edmund Scientific) that are
about 10" x 10". I put one down on an overhead projector (you
need to use the old-fashioned ones with the big boxy base) then use
something like a shoe box to create a spacer, then put the other one on
top, with a weight. That gives me a little "Pol Theater"
in which I can do all sorts of experiments. The result is projected on
the wall or a screen
I usually start with something like a clear plastic party plate
that has a pattern embossed. Show them the plate in regular light
(clear, no color) then between crossed polars, projected onto the screen.
The results are really dramatic. The color is directly related to the
stress and different thicknesses resulting from the molding
process. This opens a wonderful discussion on how fast light
travels through different materials (a great time to do the glass rod in
a beaker of water trick and Snell's Law), then refractive index (an
important optical property used in crime labs to tell where glass comes
from in a crime scene). That leads to the discussion of
birefringence (different RI sitting in different direction) which the
treasured Shinya Inoue so graphically illustrated by cutting two long
rectangles of wood: one WITH the grain and one AGAINST the grain (aobut
1" x 1" x 8"). I think there was a hole drilled
across the short end so that the wood could be suspended from a
chord, like a chime. Each block was then hit with a rubber mallet.
They make very different sounds, depending on what the impulse wave
encounters (with or against the grain). The analogy can then be
made for light. By the way, of course, Shinya being Shinya, he
stained and finished). There are a lot of follow-on
experiments: making optical wedges with cellophane tape, optical
additon and subtraction, etc. Also, if you have access to
microscopes, there are baby cameras that can be place in lieu of the
eyepiece. There are a whole raft of experiments on growing crystals
under the microscope both between crossed polars and in normal
brightfield, and, even if you don't do the Pol unit, the kids will get a
big kick out them.
I hope that this was helpful.
Best regards,
Barbara Foster, President
Microscopy/Microscopy Education
7101 Royal Glen Trail, Suite A
McKinney TX 75070
P: (972)924-5310
Skype: fostermme
W:
www.MicroscopyEducation.com
MME is now scheduling customized, on-site courses through July
2008. Call us today for details
That should get you st
At 10:06 AM 2/14/2008, Mayandi Sivaguru wrote:
Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal Dear members
of the list, We are planning to offer a one week summer program for 8th
and 9th graders on “Optical microscopy and imaging techniques”. I kindly
request your input on any available book or literature at this level with
basic geometrical optics, optical path, image formation, contrasting
techniques including polarization information and any available easy to
understand tools and kits (especially for diffraction patterns) that
could be used for the students to make mini projects.
Thanking you in advance and I greatly appreciate your suggestions and
recommendations.
Shiv
Mayandi Sivaguru, PhD, PhD
Microscopy Facility Manager
8, Institute for Genomic Biology
University of Illinois at Urbana-Champaign
1206 West Gregory Dr.
Urbana, IL 61801 USA
Office: 217.333.1214
Fax: 217.244.2496
[hidden email]
http://core.igb.uiuc.edu