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Right. Students just get to see me holding the photocopy, but
they try to
"hand wave" to get the answer. It's interesting to see how
they think, and
some of them change their answers several times!
We also discuss the word AMBULANCE and the positioning of the
letters. You
can write these with a marker on a piece of glass to show
what's going on.
Do you have the link to that cartoon?
Forum for Physics Educators
<phys-l@carnot.physics.buffalo.edu> writes:
Part of the problem is that books always talk about the left-rightmentioned. In
reversal
of mirrors, but the obvious front-back reversal is never
reality if you put L and R on your palms and look at it in amirror, the
mirror image has them on the same side, so is there really a L, Rback side,
reversal?
Don't you see the same thing as if you were looking from the
whenwould not appeal
you look at writing? If we were Australian aborigines we
to the R-L reversal, but rather to the compass pointreversal as already
noted.legend is that
Incidentally Sidney Harris has a funny cartoon on his website showing
Alice
on the other side of the mirror trying to get out, and the
she can't get out because some replaced the glass with Lexan.photocopy. All you
I assume the students are not allowed to handle the
needcourse you
to do is put your hand over it to see which hand it was. Of
havelooks the same as
to be careful to put the hand in the same position so it
the photocopy, with no reversals.careful to put
Of course you can make a non reversing mirror if you are
thethere were some
two plane mirrors at perfect right angles. As I recall
cheap children's toys that did things like that. Nonreversing mirrors
areasymmetries in your
very perturbing because you are used to seeing the
shaving mirror. When they are reversed you look lopsided.very expensive.
John M. Clement
Houston, TX
Mirrors are not well understood by most people, even my best
students. You
really have to do labs and ray tracing to figure out
how/where images form
in plane mirrors.
I show a photocopy of my palm each year and ask the kids
which hand it is.
I never get a consensus. Same thing with adults!
I have them look at the vertex of two perpendicular mirrors
for a double
image reversal. This is how others see you. They really like this!
Educational Innovations sells such a mirror, and it is
Feynman's insight
Forum for Physics Educators
<phys-l@carnot.physics.buffalo.edu> writes:
Those of us who are old enough can remember textbooks thatreferred to
images in a plane mirror as being "erect but perverted".Fortunately,
that choice of words has fallen out of favor - and
L Macisaacsimply makes it a mute point. We still have to struggle withhow to say
"Uranus" though.
Bob at PC
-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
bounces@carnot.physics.buffalo.edu] On Behalf Of Daniel
and down.'another 'SillySent: Wednesday, February 15, 2012 10:12 AM
To: Forum for Physics Educators
Subject: Re: [Phys-l] representing position and orientation
This very nice problem is discussed in a Feynman video at
http://www.youtube.com/watch?v=msN87y-iEx0
and the discussion may surprise. Dan M
On Feb 15, 2012, at 10:07 AM, chuck britton wrote:
Different representations for different situations.
This reminds me another 'representational' answer to
environment.Question' that occasionally comes up in an intro Physics
'Why does a mirror reverse left and right but not up
sez) use theof our having
I've heard 'serious' answers that 'explain' it in terms
and othertwo eyes - side-by-side - and our 'brain' figures it out
such foolishness.
An easy demonstration of what's going on is (as JD
floor or on therepresentation that works with a given situation.
If you look into a horizontal mirror (either on the
North, South,ceiling) it is clear that only up and down are switched.
plane then it'sEast and West are unaffected.
Same goes for a vertical mirror. If it's in the N-S
Down stay theonly the East-West directions that are switched. Up and
eastward, westward,same as do North and South.
Use the representation that works in a given situation.
.
At 4:07 PM -0700 2/14/12, John Denker wrote:
It is difficult or impossible to
express things in terms of northward, southward,
to do that.or other heading-related notions ... but we don't need
There are other (better) representations we can use.
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l