ISPP REMINDER                                                                                    January, 2004
HAPPY NEW YEAR ! !
OUR NEXT MEETING. . .
the 20th Annual Tri Physics Meeting: ISPP, Physics West and Physics Northwest
                                                                              . . . is at Elmhurst College
                                                                                            Wednesday
                                                                                             January 14
NOTE TIME -------- 5:30 - 9:00 p.m.
5:30 for Pizza before the regular meeting at 6:30. A map and directions are enclosed.
Earl Swallow and Marie Baehr will be our hosts.  Don’t miss it!


ANNOUNCEMENTS…
 
February 10 (Tuesday)             Northeastern Illinois University – Paul Dolan and Joe Hermanek           
(This will be a Bill Conway memorial meeting.  Bring phenomena Bill used to share)
March 9 (Tuesday)                   Loyola University Chicago – Gordon Ramsey
April 8 (Thursday)                    Lake Forest College – Bailey Donnally and Mike Kash
May 10 (Monday)                    Northwestern University – Art Schmidt
June 9 (Tuesday) (tentative)    Columbia College Chicago – Pete Insley
 
May 11, 12      Physics Day at Great America

Arizona State University in Tempe invites high school physics, chemistry, and physical science teachers nationwide to enroll in summer graduate courses in physics pedagogy, interdisciplinary science, and contemporary physics.  Modeling Workshops are included.  The program can lead to a Master of Natural Science degree.  A NSF grant provides stipends, some free tuition, and free housing.  http://modeling.asu.edu/

St. Viator High School, Arlington Heights, will have openings for physics and physical science in 2004-05. Call Fr. Tom von Behren or Dan Leyden at 847-392-4050.
 
AT OUR LAST MEETING…

John Milton (DePaul University) took a cue from Ann and Debbie and began the meeting with a phenomenon.  The Physics Teacher December issue describes on page 548 an experiment with an empty pop can and a styrofoam sheet.  John pulled out a blue block that I estimated to be about 50cm by 50cm by 7cm.  He charged the top of the Styrofoam with a fur and placed the pop can on it.  The can rolled to the edge and stopped.  He faced the can in various directions and it did the same thing.  John rubbed the block again being sure to get all the edges.  The can now rolled off the edge.  When John covered part of the block with aluminum foil, the can rolled up to the foil and stopped.  John replaced the block with one that appeared to be about 75cm by 75cm by 2cm and repeated the experiment.  Once or twice the can stopped mid board but most of the time it continued to the end.  Someone suggested John try a conducting ball so he got a ping-pong ball covered in conducting paint and tried that.  It rolled around in random patterns, starting and stopping, until it would roll off or get stuck. 

Gerry Lietz then tried to use an electrometer with an overhead dial to examine the field above the board.  He needed to hold the probe about 20cm above the block to avoid pinning the meter, so it was hard to detect variations of the field near the surface.  Nice idea though!  A lively discussion of surface charge distribution, induction, and other ideas followed.  This was an excellent phenomenological presentation.  Thanks John and Gerry.

We then did the announcements listed at the top of this Reminder.  In addition, two of the teachers from the Latin School contingent, Jonathan Legenche and Steven Cobesly are both in their first year teaching.  Ann and Debbie presented them with New Teacher Bags.






Gordon Ramsey (Loyola University) brought two mailing tubes.  One had a 5.5cm diameter and one had an 8cm diameter.  They were both about 60cm long.  Both had caps on one end.  Gordon showed that he could remove the end cap and asked, “What happens to the resonance frequency of the tube as I remove the cap?” 


Gordon brought an air blower with him to blow into the tube and excite resonance.  He showed us how it worked and we listened to the resonance with the tube closed.  He asked the question again and we answered.  In general everyone agreed that the open tube will have a higher pitch.  Some said the frequency will double.  Others weren’t sure about that.
 
The open and closed tube equations were put on the overhead along with some wave diagrams.  There was the usual discussion of pressure and displacement nodes.  When solved for frequency the equations predicted the frequency should double.
 
Gordon then sounded the closed and open tubes and passed out sheets with tube and frequency data.  In the small tube the pitch went up almost an octave (D3 and C#4) and the large tube fell significantly short (C3 to B4).  We generally agreed the shortage was due to end effects. This was a very nicely done phenomenological presentation.  Thanks Gordon.



Martha Lietz (Niles West High School) has brought “ranking tests” to us in the past.  They are always instructive.  This time she had three wooden blocks made out of 15cm sections of 2x4.  She placed a small metal weight (300g ?) on each and connected them together in a line with rubber bands hooked over thumbtacks.  She passed out a paper showing a diagram of the blocks with the rubber bands labeled.  There were diagrams showing one block, two blocks, and three blocks.  The students then were supposed to rank the forces in terms of the stretches of the rubber bands when pulled.  Which were equal and which were larger?  Then “carefully” explain your reasoning.  Then tell how “sure” you were from 1 to 10.

We gave our votes and were pretty sure we were correct (we were), but Martha said her students had to think hard and draw in the forces carefully.  Then she pulled the blocks along the table to show us we were correct.  Mike Matkovich said he connected his blocks with spring scales.


Martha gave us some sources for ranking problems that she has used and found helpful:

www.prentishall.com; Teaching Innovations in Physics and Interactive Physics by Cindy Schwartz.

Ken Bowen (Latin School) has been thinking about impedance and got the rest of us started thinking about it.  The question seems to me to be what systems can be better understood using impedance and what systems cannot.  I’m still thinking.

Nate Unterman (Glenbrook North High School) has been discussing color mixing and brought his bowling pins.  Nate turned out the lights and set the pins up on the demonstration table.  He had a slide projector illuminate them with various gels and asked us to determine the color of each of the eight pins.  We looked at them in red, blue, green, yellow, magenta, and cyan lights and tried to guess their color in white light.  Then Nate turned on the lights and we checked our guesses.  The pins were the above colors plus a white and a black.
 
Nate passed out a sheet with two pages.  The second page is a nice student worksheet.  The first sheet describes how Nate got the bowling pins and matched the paint colors with the slide colors.  Thus must be carefully done because not all gels are identical.  Nate described a nice procedure for matching gels and paints and had a few tips on painting pins. Someone suggested dichroic filters for theatre lights give a pure spectrum color but they go for $40 each.

John Thompson (DePaul University) has been looking at Gerry Lietz’s green laser pointer and wondering how it works.  Most green lasers are actually infrared laser at 1064 nm and a doubling crystal that gives a 532 nm wavelength.  These lasers are around $2000.  Could a doubling crystal be in Gerry’s $135 laser?
 
Gerry was reluctant to let John cut his laser apart to see, so John found another way.  He set up a prism and directed a red laser through it and we saw the dot on the front board.  Then he directed the green laser through it and the green dot appeared next to the red one.  He then focused a video camera on the dots and showed them on the monitor.  He then covered the paths of the green and red from the prism.  We looked closely and clearly saw a third dot.  It would be in the infrared region.  So this is the infrared beam that originates in the laser.  There must be a doubling crystal!
 
John was amazed that they could manage to sell the laser for $135.  Those crystals are very delicate and expensive.  Thanks John!
 
Ann Brandon (Joliet West High School) said whenever she teaches Newton’s 3rd Law she gives two students 5N spring balances and tells one to pull with 1N and the other to pull with 2N.  Cute!
 
Ann also brought some masks that were the giveaway from November.  When a light shines on the concave part, it looks convex from certain angles and the face follows you when you move.  I couldn’t see it, but almost everyone around me did.  I tried it at home and my family saw it (sort of).  It seems the angle of the light beam to the mask is critical.  It also helps if the light is bright.  Ann used the overhead projector.



Gerry Lietz (DePaul University) asked the questions “How does digital photography Work?  How big are the pixels?  Why does infrared look white instead of red?”
 
Gerry set up his camera 4M from a red file folder with a 22cm width.  The camera has a focal length of 4.5mm.  Gerry took the picture, and read the memory card into Photo Editor by Microsoft.  If you box the red folder the program will tell you it’s 72 pixels in width.  If you don’t believe it, you can enlarge the folder until you can see the pixels and just count them.  So
 
(220 mm/4000 mm) = (72 pixels (x)/4.5 mm)

72 pixels = .2475mm
 
1 pixel  = .0034mm = 3.4µm

We then went into a discussion on resolution.
 
Gerry had a camera he had taken apart to look at the pixels.  They are coated individually, in groups of nine, to make them sensitive to particular colors.  Then the colors are averaged.  Gerry also passed out a nice sheet (in color) from Michael McCreary of Eastman Kodak explaining how everything in the camera worked.
 
A fine discussion followed concerning why infrared looks white.
 
John Milton (DePaul) reminded us of the 1994 Demo show that ISPP did at Notre Dame.  John Bozovski videotaped it and John Milton transferred the video to CD.  He indexed the video so you can watch any of the demonstrations individually.  And he gave us each a copy.  What a great giveaway!  And another great meeting!
 
Submitted by Pete Insley

For any information regarding ISPP contact Gerry Lietz at DePaul University, Physics Department, 2219 N. Kenmore Chi. IL 60614 phone (773) 325-7333 e-mail glietz@depaul.edu
BRING FRIENDS           BRING IDEAS ! !           SEE YOU THERE ! ! !

Directions to Elmhurst College

From the North: Take the Tri-State Tollway (I-294) south to the exit marked "I-290 West/U.S. 20-Lake/Ill. 64-North Avenue." Turn left (south) on Maple and proceed across the railroad tracks to campus. (Maple Avenue becomes Prospect Avenue south of the tracks.)

From the East: Go west on the Eisenhower Expressway (I-290), following the signs marked "I-290 West/Rockford." Exit I-290 at St. Charles Road West. Proceed 1.5 miles to Prospect Avenue, then north to campus.

From the South: Traveling north on the Tri-State Tollway (I-294), go past the Cermak Road plaza to the exit marked "I-290 West/U.S. 20-Lake/Ill. 64-North Avenue." Proceed north on I-290 to St. Charles Road, west 1.5 miles to Prospect Avenue, then north to campus.

From the West: Travel east on the East-West Tollway (I-88) past the Oak Brook plaza to the York Road exit off the Tri-State Tollway South (I-294) merge lanes. Proceed north on York to St. Charles Road. Turn west to Prospect Avenue, then north to campus.

From the Northwest: If you are traveling east on I-290), take the Ill. 83 South exit. Turn east at North Avenue (first stoplight), and proceed one block to West Avenue. OR Take I-355 south to North Avenue (Ill. 64) and proceed east approximately five miles to West Avenue. Turn right (south) on West Avenue and proceed to Third Street. Turn left (east) onto Third Street and proceed to Maple Avenue. Turn right (south) on Maple Avenue and proceed over the railroad tracks to campus. (Maple Avenue becomes Prospect Avenue south of the tracks.)

From the Southwest: Take Ill. 83 north to St. Charles Road. Then travel east on St. Charles to ProspectAvenue, then north to campus.
Park in the lot marked 1 in the campus map below and enter the science center, the building in the lower right corner of campus map.