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An empirical study on a learning path on wave physics focused onAn empirical study on a learning path on wave physics focused on energyenergyVera Montalbano, Simone Di Renzone, Serena Frati

Department of Physics, University of Siena, Siena, Italy

IntroductionIntroduction National Plan for Science DegreeNational Plan for Science DegreeIn recent dec ades it has been detected in Italy a dec rease in enrollment in basic

sciences, i.e. Mathematics, Physics and Chemistry.

Italy is active since 2005 with a large and detailed plan t o remedy this problem

funded by the Ministry of Education and Scientific Research [3]

PLS (Piano Lauree Scientif iche, i.e. National Plan for Science Degree).

Strategy and me thodologiesStrategy and methodologies

Orienting to Science Degree by means of t raining

Laboratory as a method not as a place

Student must become the m ain character of learningJoint planning by teachers and university

PLS laboratoriesPLS laboratories

Laboratories which approach the discipline and develop vocations

Self-assessment laboratories for improving the standard required by graduate courses

Deepening laboratory for motivated and talente d students

methodological issues

Laboratories are realized by inquiry, i.e. students explore waves behaviour in

qualitative way, guess w hat can happen and suddenly test their hypothesis.

Complementary experience compared to what w as done in class

We focused our attention on topics in which the main difficulties in learning usually

appear [1 ] (disc ipl inary knots according to the Model of Educational Reconstruct ion

[4]) :

Waves as function of several variables: this usually is an hidden trouble. Even

brilliant students can use for long times functions of one and several variables

without any rea l understanding of deep difference.

Energy transport in order to distinguish waves from other periodic phenomena

Superposit ion principle is a fundamental concept and can clari fy many

phenomena in wa ve physics.

Analogy in waves phenomena: difficulties in this area are very common and

reported [5]).

Resonance: despite it is a relevant phenomenon which runs through almost

every branch of physics, many students have never studied it.

Everything can vibrate. Wave phenomena are everywhere. There are oscillations and

waves in springs, ropes, water. Sound and light are waves. Even more important in

physics is the wave phenomenon of quantum mechanics. When and how can it make sense

to use the same word, wave, for all these disparate phenomena? What is it that they all

have in common?

A first answer lies in the mat hematics of wa ve phenomena. Periodic behaviour of any kind,

one might argue, leads to similar mathematics. There is a more physical answer to the

questions. If it is possible to recognize deep similarities in different physical

phenomenology, then it is likely that we can describe them by mean of the same

mathemat ical tools.We proposed and are testing a learning path in wave physics addressed to talented

students. Some disciplinary knots were identified and laboratory activities were developed

in order to help understanding in learning processes [1]. Testing these activities in an

optional laboratory with high school student can be considered the first step in order to

develop a designed-based research learning path [2].

All activities are realized in an optional extracurricular laboratory within National Plan for

Science Degree .

Learning paths on waves

1] S. Di Renzone, S.Frati, V. Montalbano,Disciplinary knots and learning problems in waves physics,, Twelfth International Symposium Frontiers of Fundamental Physics (FFP12), Udine 21-23

November 2011, arXiv:1201.3008v1arXiv:1201.3008v1[[physics.edphysics.ed--ph], 2012ph], 2012

2] R.R. Hake,Design-Based Research in Physics Education Research: A Review, in Kelly,Lesh, & Baekeds.,Handbook ofDesignResearchMethodsin Mathematics, Science, andTechnology

Education,Erlbaum 2008, 493.

3] V. Montalbano,Fostering Student Enrollment in Basic Sciences: the Case of Southern Tuscany,in Proceedings of The 3rd International Multi-Conference on Complexity, Informatics and

Cybernetics: IMCIC 2012, ed. N.Callaos et al, 279 (2012). arXiv:1206.4261v1arXiv:1206.4261v1[physics.ed-ph], 2012, PLS Website, www.progettolaureescientifiche.euwww.progettolaureescientifiche.eu, accessed 2012 June (in Italian)

4] R. Dui t, Science Education Research Internationally: Conceptions, Research Methods, Domain of Research, EJMSTE, 3, 3-15 (2007);R. Duit, M.Komerek, J.Wilbers, Studies on

Educational Reconstruction of Chaos Theory,Research in Science Education, 27 (3), 339-357 (1997).

5] N. S. Podolefsky, N. D. Finkelstein, Salience of Representations and Analogies in P hysics, AIP Conf. Proc. 951, pp. 164, 2007 PHYSICS EDUCATION RESEARCHCONFERENCE , (2007);

N. S. Podolefsky, N. D. FinkelsteinAnalogical scaffolding and the learning of abstract ideas in physics: An example from eletromagneticwaves , Phys. Rev. ST Phys. Educ. Res. 3, 010109

(2007)

6] J. N.Shive, Similarities of WaveBehavior (1959), http://techchannel.att.com/playhttp://techchannel.att.com/play--video.cfm/2011/3/7/AT&Tvideo.cfm/2011/3/7/AT&T--ArchivesArchives--SimilaritiesSimilarities--ofof--WaveWave--BehaviorBehavior, accessed 2012 June; J. N.Shive, R. L.

Weber, Similarities in Physics, Wiley-IntersciencePublication, New York 1982.

D ee p en i ng l a bo r at o r ie s f o r m o t i va t e d a n d t a l en t e d s t u de n t s r e al i ze d b y

Department of Physics, Univers ity of Siena (V. M., S. Di Renzone*, S. Frat i*)

L iceo Sc ient i f i co A ld i Grosseto (G. Gargan i )

PLS laboratories: Waves and energy (3 stud.) Sound and sur round ings(4 stud.)

Opt ional laborator ies, ext racurr icu lar learning paths, al l act iv i t ies real ized at Department of Physics

We are meet ing students for 3 hours almost every month and planning to c ont inue for last 3 years of

high school (15-18 hours each year)

S t ud e nt s e n de d t h e i r l e ar n in g p a t h o n w a v e s i n c l a ss b e fo r e l a bo r at o r ie s s t a rt .

M or eo ve r, t h ei r c l as s m a de an in st r uc t i on t ri p t o o ur d ep a rt m en t a nd p er fo rm e d a st a nd ar dlabora tory exper ience on d if f rac t ion and in ter fe rence wi th l igh t (e .g. in f igure) .

Students works together or in s imilar act iv i t ies, somet imes with dif ferent purposes, for the f irs t 10

labs. They present an annual report to their physics teacher for assessment .

By check ing the resu l t ing data in t he f i r s t year , i t a rose some learn ing d i f f i cu l t ies espec ia l ly in

ac t iv i t ies re la ted to t he labora tory [1 ] .

* t eachers enro l led in Master In Educational Innovation in Physics and Orienting - University of Udine

References

Shive Wave M achineWe chose to start by a series of activities performed by student by

using a Shive w ave machine[6]. This device, developed by Dr John

Shive at Bel l Labs in 50, consists of a set of equally-spaced

horizontal rods attached t o a square w ire spine.

Displacing a rod on one of the ends will cause a wave to

propagate across the machine.

Torsion waves of the core w ire translate into transverse waves.

Measures were obtained by using a camcorder and extract ed f rom

the captured images

dependence on space-t ime o f w aves impu ls ive and per iod ic waves

wave length and f requency

energy t rans fer

speed of p ropagat ion

superpos i t ion pr inc ip le

re f lec t ion and t ransmiss ion

For example, by coup l ing core w i res o f two Shive

wave mach ine w i th d i f f e ren t rod lengths , animpu ls ive wave can be re f lec ted and t ransmi t t ed

through the discont inuity. Students can measuref rom captured images a l l wave ampl i t udes and

speeds and ver i fy that energy is conserved.

Pulse star t ing from short rods

Pulse star t ing from long rods

Similarities in PhysicsShive Wave Machine

Pros

- easy student interact ion

- superposition principle

- measure , T, v

- energy considerations

- simple study of waves

stationary and resonance

Cons

- one-dimensional wave

- no study of diffraction

and interference

Shive Wave Machine was developed in order to point out

similar features of waves as they propagate, reflect,

superpose, resonate, etc. [6].

Analogies are displayed among the behaviors of waves onmechanical, acoustical, electrical, optical, electromagnetical

systems.

Students were invited to consider

different wave phenomena and find

speed, frequency an wavelength range

Mechanica l waves: ripple tank, vibrating string,

vibrating membrane, .. . .

Pressure wa ves: sound, ultrasound, .. . .

Electromagnetic waves: radio waves,

microwave s, light, infrared, ultraviolet,

X rays, gamma rays, .. . . ..

Then, they had the ta sk of recognizing beats, reflection,

refraction, interference, diffraction, Doppler effect.

Sound refraction

Snells law for waves

on a liquid surface

ResonanceIn order to introduce students to resonant systems, we start

with a mechanical system, a ma gnet suspended from a spring

which can be forced by induction by an electromagnet.

Students studied this system focusing on energy.

Electromagnetic induction can easily transform mechanical

energy into electrical energy. Moving magnet induce a EMF in

the solenoid that can move elect rical charges.

Enveloping the outside of the e lectromagnet w ith aluminum is

possible to observe the damping due to eddy currents

Pendulum and dumping: copper plates were placed on theelectromagnet for studying damping vs thickness of the metal.

The dr iv ing force in the exper imentalsetup is suppl ied by a solenoid. To

a l lo w i t s m od ul a ti on , a m o sf ett ransistor acts as an elect ronic

switch. A funct ion generator appl ies

a square wave of given f requency to

t h e m os fe t g at e, r es ul ti ng in amodulat ion of the DC current

provided by the power supply to thesolenoid. The solenoid forces the

magnet t o osc i l la te a t t he samefrequency of the square wave:

changing the f requency is i t possible

to study the resonant condit ion of

the magnet-spr ing system.

Can induct ion t ransform

electr ical energy in

mechan ica l energy?

Students d iscover t ha t t h is isnot always possible .

If they try to modulate anelectromagnet, only in fewcases the energy transfer ismassive.They changed f requencies inthe system on the lef t and

observed that only for onefrequency there is a massive

osci l lat ion of the mechanicalsys tem.

They measure the per iod of t he osc i l la t ing sys tem wi thout

e lec t romagnet and comparethe f requency wit h the one

measured before.

Sal t fee ls soundBy using a speaker connected to a funct ion generator, aresonant system can be obtained by placing a metal plate

over i t . When sound is resonant with one f requenc y of theplate, salt s tar t jumping leaving f rom the v ibrat ing surface

and cumulat ing in f ixed zones. The f igures formed by salt

(Chladni f igures) depend on the shape of plate, mater ial ,

thickness and boundary condit ions (existence of constrained points) .

In this case is very easy to recognize resonance.

The RLC circuit w as taken in account too.

Work in progressT hi s y ea r, t h e f in al t a sk w a s t o a na l ys e d if fe re nt n at u ra l p he no m en a i n

o rd er o f c h oo si ng t h e m o s t s ui t ab le f or e ne rg y t r an sf er .

These laboratories seemed to be very successful, but sometimesstudents showed some learning difficult, in collecting properly and in

using correctly the experimental data in order to describe physical systems, because theyare little accustomed to face open situations. Students are very smart in using new deviceor in simple lab task such as measure a period, but they are showing a certain naivety indealing with open problems .

In the meant ime, we are real iz ing a system that can be used for looking for resonances by

us ing the Shive wave mach ine, in o rder t o improve too ls on ana logy .

University of SienaUniversity of Siena

PLS areaof Univers ity of Siena

Next year it will be faced the problem of tuning a resonant system inorder to maximize the energy transferred from the naturalphenomenon chosen by students.