First semester sophomore physics:
The advantages of waves &
oscillations with semi

coordinated lab
Walter F.
Smith
Physics
Dept. Haverford
College
Haverford PA
Conference on Laboratory Instruction
Beyond the First Year of College
Philadelphia, July 25, 2012
A tension in education:
depth vs. breadth
Sophomore physics:
varies quite widely
One common approach:
Modern Physics
Relativity
Quantum mechanics
Nuclear physics
Particle physics
Statistical mechanics
Approach to sophomore physics at Haverford College:
Rigorous quantum mechanics in lecture and lab
Lecture:
Advantages:
•
Quantum mechanics is very exciting to students!
•
Central to many hot areas of research (e.g. q. computing, q. info)
•
Philosophically challenging (e.g. entanglement, locality, …)
•
Required for many of our most impressive results (transistors,
solar power) and most important challenges
•
Gives students a real insight into the physics major
before they declare
Disadvantages:
•
Only 1

2 weeks on relativity in first 2y (during 1
st

year
e&m
)
•
There are many exciting areas of physics that don’t involve
q.m
.
http://www.latimes.com/news/science/la

sci

quantum

entanglement

20120707,0,802675.story
Our experience at Haverford:
•
Originally, students began study of quantum right after two
semesters of intro
•
Most students struggled, achieved poor understanding
•
New system:
•
Semester 1: Waves and Oscillations
•
Semester 2: Quantum Mechanics
•
Works very well!
•
Increased number of majors
(~12 per year, with student
body of 1200)
•
Excellent, supportive
atmosphere among majors
Advantages of Waves & Oscillations in the sophomore year:
•
Important in most areas of physics
•
Electricity & magnetism
•
Anything involving quantum
•
Acoustics
•
Plasmas
•
Nanoscience
•
Provides exactly the mathematical ideas and techniques
needed for quantum (and many other areas), in a less
intimidating classical context
•
Differential equations
•
Complex exponentials
•
Matrix math
•
Hilbert space and orthogonal function analysis (e.g.
Fourier analysis)
•
Eigenvalue
equations
•
Bra

ket
notation
Advantages of sophomore Waves & Oscillations (
ctd
.):
•
Most of material is new to students (e.g. coupled
oscillators), but connected to things they’ve studied
before & understand
•
Gives students a feeling of the challenge they will see in
upper

level courses
Text:
Connections to current research:
Whale calls:
Total internal reflection fluorescence microscopy:
Prof. Christopher Clark, Cornell Univ.
A.
Gunnarson
et al.,
Nano
Letters
8
, 183

188 (2008).
Connections to “everyday” life:
Magnetic
Resonance
Imaging
Quartz crystal
f
rom a watch
Dr. Erhard
Schreck
Web support with custom

developed
a
pplets & links to web resources
Custom

developed
c
oupled pendulum
a
nd Hilbert space
applet
Link to
Physical Review Focus
summary of
Physical Review Letters
paper on bat sonar
Prof. Rolf
Müller
, Shandong Univ.
Bra

ket
notation for coupled oscillators
•
Refreshing writing style
•
Humor when appropriate
•
Check it out Thursday in Poster Session I
Semi

coordinated lab:
Goals of our first

semester sophomore lab:
•
Transition to more independent lab work:
•
Second semester sophomore lab
•
Advanced lab (junior / senior)
•
Research
•
Provide common background of experimental expertise:
•
Simple electronics (input & output impedance, scope operation,
op amps)
•
Better understanding of optics
•
Coherent presentation of results
•
Three oral reports
•
Two full

length written reports
•
Reinforcing data analysis: Uncertainty analysis, curve fitting
Another tension in education:
creativity/exploration vs.
learning the ropes
Another tension:
Challenging your students to stretch themselves
vs. Discouraging them
Oral reports:
•
Presentations based on data graphs, tables,
etc. (not PowerPoint)
•
Given to an instructor
•
Presentations in pairs
•
Typically about 30 minutes
Overview of the lab:
Another tension:
Reinforcing understanding vs. introducing new material
•
At a variety of intervals
Connected to old material
(reading, class, problem sets,
lab, exams, other courses,
research)
•
Using different parts of the brain
•
New context
Half

credit, usually taken in the same semester as the
lecture component
First five weeks are single

week labs, done in unison by pairs,
coordinated with lecture.
Week 1: Input and output impedance for DC circuits
•
Essential concepts for all electronics
Week 2: High

& low

pass filters
•
Connects to complex notation for AC circuits in
lecture
Week 3: Resonant circuits
•
Connects to ideas in lecture
Week 4: Diodes
•
Crystal radio; synthesizing concepts
Week 5: Op amps
•
What is an amplifier? What is gain?
•
Feedback
•
The connection between a schematic & physical
circuit
•
Debugging
•
Last 9 weeks are a series of two week labs (plus a week off!).
•
Done in rotation by pairs of students.
•
Not coordinated with lecture.
Why only semi

coordinated?
•
Equipment costs
•
Allowing students to encounter some things in lab first
•
Variability in timing between the lecture & lab is OK
•
Less sense of competition for fastest completion
•
Students who’ve done the lab previously help the current
students, building camaraderie.
•
Dispersion relation of water waves
•
The beginnings of how to be
really clean
•
Challenging non

linear curve fitting
•
Dispersion relations can be
non linear
•
Torsional
oscillator (
TeachSpin
) & coupled oscillators
•
Connects to key concepts from lecture
•
Further practice with scopes, function generators
•
Computer acquisition of voltages
•
Reinforces concepts of Faraday’s Law, and creating
B
with current
wiki.brown.edu/confluence/display/
PhysicsLabs
/Experiment+120
•
Diffraction as a Fourier transform and spatial filtering
•
Connection to lecture
•
Deeper understanding of optics
•
Practice thinking in reciprocal space
•
Simple optical design exercise: beam expander
•
Optical setups using research

grade components
•
Aspects of laser safety
www.doitpoms.ac.uk/tlplib/DD1

6/image.php
•
Ultrasound imaging
•
Applications of wave ideas to a new context
3B Scientific
Shortcomings include:
•
Main equipment used for two of the two

week labs will never
be used again. (water waves, ultrasound)
•
In our current version of Advanced Lab, students don’t revisit
op amps. Students rarely use them in research.
•
Because the two

week labs are only semi

coordinated, the
connection to lecture is different for different students
Conclusions:
•
Sophomore:
•
waves & oscillations first semester
•
quantum mechanics second semester
•
semi

coordinated labs
•
High level of student interest
•
Students know what they’re getting into when they major.
•
First semester labs continue building a good foundation of
experimental skills and intuition.
•
Helpful to have a connection between lab& lecture, but exact
coordination is not necessary, or even always preferred.
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