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-----Original Message-----Behalf
From: Forum for Physics Educators [mailto:PHYS-L@lists.nau.edu] On
Of Kossompaint
Sent: Wednesday, June 04, 2003 6:52 PM
To: PHYS-L@lists.nau.edu
Subject: Re: out-of-the-box thinking
Howdy-
From: John S. Denker
Sent: 6/4/03 4:39 PM
In your classes, do you set up situations where
out-of-the-box thinking is appropriate? Necessary?
Is it part of the routine procedure? Does it
get rewarded? Can you share some examples?
I am fond of including essay questions on my tests.
One of the questions I often ask during the acceleration section is
Below is a series of lines made by a machine that marks
the stripes on the street. If the machine always sprays the
for the same length of time, is the machine speeding up, slowingDefend
down,
maintaining a constant velocity or that can't be determined.
your answer.the
--- --- --- --- --- --- --- --- ---
Most students say that the machine is speeding up, giving the usual
reasons.
This is a really easy question since we use tape timers in the lab.
Over the years, though, a few students have noticed two problems with
question. Do you see them?them
Should I change the question, or isit good to let some students find
on their own? I give bonus points to students who find significantblind
alternative answers or flaws. I hope that this encourages students to
think
outside the box on tests, but it can also cause students to go down
alleys on other tests.liquid
* * *
For a bonus on the final I usually have this optics question.
In front of you is a soap dispenser. Ignore the orange soap at the
bottom; it is
not part of this question. Instead look at the two layers of
atindex
the top. The
top one is clear and the bottom one is blue. Which has a higher
ofis
refraction?
Since you can't see it., I'll tell you that the soap dispenser is a
cylinder. The students get to actually play with it.
Most of the students say that the blue liquid is one with the higher
refractive index because it is denser. Unfortunately, the clear liquid
the one with the higher index.the
I expect them to discover this by noticing that the when looking down
through the clear to the blue, there is significant total internal
reflection, but none the other direction. The vast majority who get
question right do this.that
However, several use the dispenser as a cylindrical lens and notice
the
clear part magnifies more than the blue part.
I'm fine with either answer, obviously.
Marc "Zeke" Kossover