Re: [Phys-l] unbiased experiments +- index of refraction

["LaMontagne, Bob" <RLAMONT@providence.edu>]

Maybe I'm just old and thickheaded, but 90% of what you have described is simply what is usually tagged as a "meaningful lab experience". Your claim is that that research has shown that these "discovery" or "inquiry" approaches are superior to traditional lab exercises, but you examples are what I feel are simply part of the spectrum of labs that are well thought out with specific goals in mind. I'm not sure what they are actually being compared to as a control. I really don't think there are many experienced faculty out there that simply have students robotically go through cook book procedures and call it a lab.

I guess I really don't have a grasp of what makes these "discovery" labs different enough to warrant a new name and an enthusiastic set of disciples. I certainly see that the motivation behind this approach is different enough to assign a new name, but the nitty gritty details of what happens in the labs sounds too familiar and close to what reasonable people already do.

Bob at PC

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of John Clement
Sent: Wednesday, May 13, 2009 12:17 PM
To: 'Forum for Physics Educators'
Subject: Re: [Phys-l] unbiased experiments +- index of refraction

> I hope there's more to "discovery labs" than this. I do an identical
> exercise with springs - one group studies the effect of mass on period,
> another studies the effect of amplitude, etc. The only difference between
> what I have described and what you have described is the point at which
> they encounter the equation for the period - at the begining of the
> exercise or at the end. I hope someone who has a strong definition of what
> a discovery lab actually is will chime in.

Actually the students shouldn't "encounter" the equation, they should
determine it from the lab.  The Modeling approach has them graph the data,
and if it is a straight line, just find the equation.  If it is not, then
they try different ways to make a modified graph by changing the X axis.  If
they have X vs t and it "looks like a parabola" graph X vs t^2 and see if
they get a straight line.  This is a fairly old fashioned approach.  Of
course the students have to follow some rules for taking the data so that
the data is analyzable by this approach.  If it is a 1/sqrt(x) relationship
they have to first make a graph of 1/x and then by noticing the curvature
try 1/sqrt(x).  So for most situations all they need is to recognize is
linear, inverse, square, and square root relationships.

In other inquiry programs they do use some fitting routines and this is
available in programs like Loggerpro.  I have come to like the Modeling
approach because it is less of a black box.

So an inquiry lab is where the students do NOT know what they will find, and
the vocabulary terms have not been introduced except where necessary.  So
for example period and frequency are necessary terms for the spring lab
described above.  In an inquiry lab students have to derive where possible
the equations, and represent the data graphically, pictorially, in words,
and finally by equations.  Then they have to present their results to each
other, and there may be a teacher led wrapup.

WARNING:  I have tried to provide a large number of tips and ideas.  As
usual I went overboard.  Some of this may be obvious, and some may not.  All
of this is found in the research papers and Arons.

However, the approach which works the best then uses the rest of the
learning cycle.  There is generally a wrap up where the teacher can define
terms.  At this point the students have the equation, but you have not used
the specific terms for the concept.  So if they measure the motion of a
battery driven car they have not heard the word velocity until that point.
Then the students solve problems.  This follows the learning cycle which is 
1. exploration
2. concept development (lecture?, vocabulary term definition)
3. application

Application could be other things than solving problems such as using the
initially established model to study other things.  Exploration has to
generally begin with some concrete preparation for the activity.  One can
also have a motivational demonstration here.  The preparation can be teacher
led, or it can be in a lab sheet form typical of Real Time Physics.

The example of the motion of the car as an inquiry lab has the students
making marks (placing markers) on the floor at each second or every other
second.  Then they have to draw the pattern of the marks, and graph the
data.  The pattern of the marks is called a motion map or a strobe diagram.
Notice that you have set up the condition that time is independent and
position dependent.  Usually it is better to have them solve problems using
only graphs and motion maps.

Virtually any lab can be turned around this way, but it is important to
integrate it into the teaching so it constitutes the first experience with
the concept before any terms are discussed.  Notice the lecture occurs in
the middle.  Generally inquiry labs do not have the traditional lab report
format because there is no hypothesis, just a question "What the heck
happens".  The conclusion is the derivation of the equation and the
presentation of the graph and picture, and it is important that a correct
description of the equation be made.  Students can be asked to describe the
meaning of the intercept and slope for the modified straight line graph.  So
for the car example they should say the equation x = 3m/s t means that the
car traveled 3m each second.  You can not accept the word per in the
meaning.  This is straight from Arons.

There are examples which are purchasable.  The Real time physics labs by
Thornton, Sokoloff are good templates for one style of lab.  Workshop
Physics is a complete course based on inquiry labs which is purchasable.
They are more cookbook than the Modeling method.  Modeling starts with blank
sheet of paper and graph paper.  Students are introduced to the equipment
and shown what it can do.  They brain storm the variables, and then with
your help they decide which variables can be actually measured.  Then they
measure them, and create the lab reports.

Now there are certainly labs where the students would never figure out the
equation.  So if they measure the incident and refracted angles they can do
a graph.  They can even get an approximate equation, so there has to be a
point where you suggest the functionality or give them a sheet where it is
derived using a simple diagram.  They can then use the equation to make a
modified graph to verify that they get a straight line, and the index can be
determined from the graph.

Then there are labs where there is no possibility of taking data because of
physical or time constraints.  Newton's gravitational law is an example.
However they could take data from a simulation.  I created one at:
<http://users.hal-pc.org/~clement/Simulations/Physlets/Gravitational/Gravita
tional%20Force.html>
Or go to www.hal-pc.org/~clement
Then Science simulations
Then to Gravitational force

There is evidence that simulations can work fairly well, and sometimes
better than physical experience.

Modeling generally has a fairly rigid lab report style, but notice that the
results are aimed at building understanding of the phenomena.  Some of the
purchasable labs have vital questions interspersed between activities, and
are structured to help students build a coherent model of the phenomena.

Incidentally this is generally called guided inquiry not "discovery" because
the word "discovery" has had some bad connotations.  In the past, various
teachers tried giving the students stuff to work with and let them play with
it in the hopes that they would "discover" physical principles.  The amount
of guidance depends on the students.  If you have all students who score
~10/12 or above on the Lawson test you can probably eventually give them
equipment and let them go at it.  But in the early labs they have to be
prompted to figure out the variables and be taught how to use the equipment
to measure them.  Students at the lower end of the Lawson test will always
need more guidance.  Modeling by providing a fairly rigid format may work
better with lower level students.  Curricula like RTP have a lot of reading
in the lab forms, so students who are very allergic to reading may not take
to them well.  So of course it is your judgment what style to use.

The Modeling style of teaching does not use a huge number of labs.  It only
uses one or sometimes 2 labs every few weeks as a paradigm at the beginning
of the cycle.  Workshop Physics has a studio format and uses many more labs
or lab activites.  There is no evidence to suggest that one is distinctly
better than the other.  There are other materials which are purchasable from
the AAPT.

And when students have finished solving problems they need to present the
solutions to each other and ask each other questions.  If the teacher stands
there and presents solutions, the student thinking stops.  Actually it is
better if students can struggle with an initial hard problem which is
solvable by the group, but not by the individual.  Then after solving it the
teacher can present an algorithm which might be useful, and then give some
more "rich context" problems.

So inquiry should not stop with just the labs, it needs to extend to the
problem solving.  Michelle Perry showed that algorithms can shut down
thinking and prevent transfer, but Schwartz showed that algorithms after
struggling with a difficult problem may not prevent transfer.

Notice that along with the inquiry it is necessary to have students
represent the physical concept by graphs, pictures, words, and lastly
equations.  If possible have them present all of these when doing problems.
There is evidence that kinematic problems should first be solved using
motion maps and graphs without use of equations.  Then equations can be
encouraged later.  The trick here is that students have to use and
coordinate the various portions of the brain which independently make sense
of the phenomenon.  They have to be able translate between these various
representations for full understanding.

But one step at a time is advisable.  If you are already using multiple
representations, then converting verification labs to inquiry should help.
But getting some of the published PER curricula can give you some instant
labs, or ideas for modification of existing labs.

Actually a lab where one measures that refraction index after already
knowing the equation can be inquiry if the students compare the values, and
can use it as an application.  One application would be forensics.  In this
case the object of the lab is to learn about the materials with the
incidental practice in finding the refraction index.

As an aside why is it usually index of refraction when refraction index is
plain simple English.  We say consumer index not index of consumers.  I
suppose it is similar to what do you say when you greet someone in the
morning (good morning), but how about the afternoon and night?  You don't
say good night as a greeting, but rather as a leave taking!  This is our
Germanic language heritage.  Index of refraction may be a foreign derived
form, and not good sturdy Germanic English.

John M. Clement
Houston, TX

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