Transcript slides - University of Colorado Boulder

Developing and Researching PhET simulations for Teaching Quantum Mechanics
Sam McKagan, Kathy Perkins, Wendy Adams, Michael Dubson, Chris Malley, Sam Reid, Ron LeMaster, Carl Wieman
University of Colorado at Boulder
American Journal of Physics 76, 406 (2008)
http://phet.colorado.edu/quantum
Research on Student Learning with QM sims
PhET Project Overview
The Physics Education Technology (PhET)
Project is an on-going effort to create a suite of
interactive simulations and related education
resources that aid in the teaching and learning of
physics.
Interactive Lecture and Homework
– Photoelectric Effect
Interactive Lecture - Davisson-Germer: Electron Diffraction
Why did Davisson & Germer see electrons deflected only at certain angles?
[accepted to AJP; arXiv:physics:0706:2165]
All students (N=74)
After All students (N=59) Students who read (N=38)
7%
After
8%
reading,
21%
1%
lecture
36% 31%
before
47%
32%
w/ sim
92%
lecture
29%
w/ sim
Would the ammeter read zero current
or a non-zero current if you were to:
a. Double the intensity of the light? Why?
b. Increase battery voltage? Why?
c. Change material of target? Why?
•Elaborate Java- and Flash-based simulations
•Support for educators and students with resources for
both teaching and learning with these simulations
•Developed using the results of education research and
feedback from educators
•Research to formally assess their influence on student
learning and attitudes in a variety of settings
•A large number of simulations exist and are being used
in introductory physics courses around the country
•Can be used in lecture demonstrations, recitation
activities, or homework assignments
•All PhET simulations are free and available at
http://phet.colorado.edu
a
b
c
N
UW w/o Photoelectric Tutor (PT)
UW w/ PT [see Steinberg et al. AJP 64, 1370 (1996)]
40 20 65
85 40 75
26
36
CU Fa05 (reformed curriculum w/ sim)
87 85 91 189
CU Sp06 (reformed curriculum w/ sim)
88 84 86 182
CU Fa06 (reformed curriculum w/ sim)
78 77 90
94
CU Fa07 (partial implementation of reforms) 72 52 69
65
electrons are waves, explain with interference:
e.g.: ‘The electrons were only detected at certain angles because they were interfering
constructively and destructively. It was important because it meant they were acting like waves.’
electrons are waves, no explanation:
e.g.: ‘The reason for this result of seeing electrons only at certain angles is matter waves. The
electrons are traveling with a certain wavelength, making it so they can only be deflected at
certain angles.’
non-wave explanation:
e.g.: ‘Shooting electrons at a neatly arranged lattice, the electrons that bounce off will have a
higher probability of hitting another atom. Since all the atoms in the lattice are neatly
arranged, they will create a series of pathways that the electrons will bounce down. Therefore,
the angles they observed were the angles at which the electrons bounced down these “tubes”.’
blank / no explanation:
e.g.: ‘You got me. I didn’t read.’
PhET simulations in Quantum Mechanics
ANIMATION
Fundamental Principles
Watch electron waves
tunnel through barriers
Quantum Tunneling
and Wave Packets
Classic Experiments
VISUALIZATION
Visualize not just the interference
pattern on the screen, but the
process that creates this pattern.
Quantum Wave
Interference
Fire the
photon gun
Models of the
Hydrogen Atom
INTERACTION
Davisson Germer:
Electron
Diffraction
See how photon behaves as a wave as
it travels through space, and a particle
when it hits the screen.
Change the
spacing and
radius of atoms
See
electron
waves
diffract
off atoms
Rutherford Scattering Stern-Gerlach
Experiment
Fourier:
Making Waves
Find the tumor.
Conductivity
See spins
deflected
through
magnets
Semiconductors
Grab the semiconductors and put
them in the circuit
Lasers
Invite to
interact
Double Wells and
Covalent Bonding
Neon Lights & Other
Discharge Lamps
Configure your
atom’s energy
levels
Visualize phenomena that you can’t
observe directly, such as atomic
excitations, electrons, and photons
Nuclear Physics
Blackbody Spectrum
Band Structure
Directly manipulate fourier
components and get instant
feedback on how this
changes the transform.
See electrons ejected from plate with
varying speeds. Watch them speed up or
slow down when voltage is applied.
View light as photons or
waves. Compare and contrast
these representations to get a
complete picture
Compare the
spectra of the sun
and a light bulb
In-Class/Lecture
Use the sims as…
• an effective means of communicating the instructors’ visual
model to the students.
• a means for interactive engagement within class using the
Peer Instruction model with simulation-centered concept tests
or interactive lecture demos.
• a complementary learning-support tool for classroom demos.
• a short pre-class activity to prepare students for class.
Homework
Use the sims as…
• a method to promote active thinking with inquiry-based exercises designed
around the simulations.
• an alternative to or supplement for traditional introductory physics labs.
Photoelectric Effect
Sample Homework Problems
Lasers:
Student Responses:
Discharge Lamps
Instructors observed
that most students did
not know the correct
answer initially, but
many were able to
figure it out through
discussion. Graphs that
students drew, before
seeing multiple choice
options, closely
matched given options.
Laser explodes if
it builds up too
much power
Set up a chain reaction
Student Responses to Quantum Sims
Teaching with PhET simulations
Sample Concept Test
Simplified MRI
Photoelectric Effect
See time evolution of
wave functions
CONTEXT
See
electrons
jump
energy
levels
See the
paths of
alpha
particles
deflected
by
nucleus
Quantum
Bound States
Applications
“Great sims, I can't imagine QM without them.”
“The simulations were the best part of class, they practically answer physics questions all by
themselves. I would recommend continuing to develop these and add more. Without these I think I
would have been lost in the course.”
“I definitely not only enjoyed the simulations, but I'd go as far to say that the simulations taught me
the most about the course because I could really visualize the inner workings of the physics
processes that we going on.”
“I thought the simulations were great. It helped me to gain intuition about the topic. This is
especially useful in quantum mechanics where
Ranked one of the most useful aspects
it is not normally possible to directly observe
of the course on end of term survey:
the described phenomena.”
How useful were the following for your
“The photon ray gun I first saw in lecture and
learning? (1 – not useful, 2 – a little, 3 –
that was very important to understanding the
some, 4 – a fair amount, 5 – a great deal)
spread out nature of photons. I used the laser
posted lecture notes:
4.3
simulation on my own first and had to play
with it to get it to lase, which was a good
the lecture period:
4.2
learning experience.”
“This is what really clarified the difference
between P and N-type and to figure out what
orientation/arrangement is required for a LED
to work.”
“I related to this, for my mother has brain
cancer. She has MRIs frequently as you could
imagine. Now I know what is really going on
every time she has one done.”
Quantum Wave Interference
the homework:
the simulations:
posted homework solutions:
studying for exams:
problem solving sessions:
the textbook:
4.1
4.0
3.8
3.7
3.5
3.2
Acknowledgements
The authors thank the Hewlett Foundation, NSF, and the Kavli Operating Institute
for providing the support for the PhET Project. We also thank all the members of the
PhET Team and the Physics Education Research at Colorado group (PER@C).