Physics 128A, Advanced experimental physics, Fall 2013
In Physics 128L, you will work through a set of modern
physics experiments. In the process you'll learn how to use several
types of equipment, plan and execute a measurement,
collect and analyze the data, draw specific and substantiated
conclusions, and present it all in a scientific manner.
David Stuart, email@example.com, Broida 5113.
Teaching assistants: William Flaherty, Johnathon Frey, Alexander Walter
Bob Pizzi (firstname.lastname@example.org)
and Dan Bridges (email@example.com)
Below is a list of announcements and useful links; it will be updated over time.
- If you are enrolled in the course via extension, so that your
name does not appear in the standard roster, please send me an email
so I can make sure that you are on the mailing list.
- The lab assignments for the Monday/Wednesday section are
- The lab assignments for the Tuesday/Thursday section are
- The first day of class is Thursday, Sept. 26. We will meet in
Broida 3314. If you are in the MW section, then the first day will
be Monday, Sept. 30th, also in Broida 3314.
- A lab notebook. This must be a bound (not looseleaf, not perforated) notebook,
containing quad-ruled paper (aka graph paper).
You will need TWO of them, since the TAs will be grading one lab
while you need to be writing up the next one.
If you have a carbon-paper notebook, then a single notebook is acceptable
because you can keep the carbons while the TAs grade the originals. However, I encourage you to go
with the two notebook approach.
- Access to the lab writeups.
The bookstore sells a bound copy, but the same information is available here.
- Access to data analysis software. Wolfram's Mathematica
It is installed on all lab computers, many UCSB computer-cluster computers, and in the PSR.
If you want a copy on a personal machine, you can buy a ($45)
one-semester or ($74) one-year temporary license, or a ($140) regular copy,
There is no physics department or UCSB license with additional discounts.
You may also use igor
which are installed on all the lab computers,
or the online plotter.
MS Excel is insufficient.
- A place to keep your computing work-in-progress.
I recommend a USB thumb drive, but some students may prefer
uploading data to Dropbox, email, or some such.
(Data will usually survive week-to-week on the computers in lab,
but they're multi-user computers so do not trust this.)
- A sourcebook for statistics and data analysis.
An Introduction to Error Analysis: The Study of Uncertainties in Physical Measurements, by John Taylor.
Last year some people got along with Internet resources.
During the first week, Sept. 26 - Oct. 3, we will discuss introductory material and do some common exercises.
The remainder of the quarter will be divided into four two-week
blocks during which you will do experiments of your choice selected
from a set of 13
You will do 4 of these.
Enter your preferences via doodle before Saturday. (M/W students
should do that
T/R students should do that
During the 10th week, you'll carry out a measurement of your own design.
Each "block" will have the same format.
- "Pre-lab lecture week": Sep 26 - Oct 3. We will meet in Broida 3314.
- Experiment Block #1: Oct 7 - 17.
- Experiment Block #2: Oct 21 - Oct 31.
- Experiment Block #3: Nov 4 - 14. (Holiday on Nov 11)
- Experiment Block #4: Nov 18 - Nov 28. (Holiday on Nov 28)
- "Design your Own Experiment" week: Dec 2 - 5.
- Final exam week: No activity.
- On Day 1, you and your partners will show up (having read the
lab and met with your lab partners)
prepared to give a short, 2 or 3 slide talk introducing it.
Every group must prepare such a talk; a random subset will be picked to actually deliver it.
These talks are worth 15% of your grade.
- On days 1-4, you will work independently on the labs,
keeping all of your data/procedures/observations/comments in a
professional-style lab notebook.
The TAs, staff, and professor will circulate to help you.
The notebook is worth 60% of your grade.
The grading breakdown for the logbooks is here.
Attendance is required, firstly because your labmates expect you to work as a team, and secondly because we're paying attention.
- On the first day of the next block you must hand
in the previous block's notebook, plus a 2-3 page synopsis or mini-writeup.
The writeup is worth 25% of your grade.
The grading breakdown for the papers is here.
- Learn how to perform careful, organized, documented and systematic measurements.
- Learn proper methods of data analysis.
- Learn how to draw specific and meaningful conclusions.
- Develop a tough-minded and skeptical scrutiny of results.
- Understand issues of precision and uncertainty.
- Become familiar with operation of standard equipment.
- Learn how to interact with equipment you have not used before.
- Appreciate the limitations of apparatus.
- Learn to clearly and concisely present your methods and results, both verbally and in writing.
- Learn general science-world conduct such as collaborating with a
partner, following safety practices, keeping an honest lab notebook, writing concise, sensible reports, and giving short presentations.
You will also learn some modern physics, by doing it.
- Learn Mathematica (STRONGLY PREFERRED) or another reasonably-professional data analysis system.
(If the Mathematica learning curve is too steep, the "next best thing" is Igor Pro,
a spreadsheet-like program also installed on the lab computers.
If you need to retreat temporarily to a spreadsheet like Microsoft Excel or
it's better than nothing, but a spreadsheet-dependent semester will score no higher than B.)
For simple plotting, you may also use an
that can then import the data to Mathematica.
- Have you given a public talk before? Most people haven't at your level, but in a few years you will.
Consider these talks as practice for your first APS meeting.
Frank Hertz experiment
For reference, these were probably 10-minute talks.
- The paper on each experiment should be a short (2-3 page) synopsis of the experiment with an abstract,
an introduction, statement of the experimental method, discussion of
results with ~ 2 relevant figures, and conclusions.
The idea here is that you learn how to selectively and concisely
present relevant data and present a coherent, conclusive result.
A sample is shown here: example lab pdf
(sources: latex, figure,
There are important safety issues in any lab work, of which you must be aware.
Some examples of safety hazards are intense light sources (lasers and gas discharge tubes),
electrical hazards (high voltage or current), radiation sources (radioactive substances or X-ray machines),
I require that you start each experiment by doing an assessment of the safety issues.
You will need to take steps to carry out your experiments safely; this is part of acting like a professional experimentalist.
- Look for safety-related information in the lab manual.
- Look for safety-related information in the equipment manuals.
- Ask an instructor about anything that concerns you.
- Include safety in the planning discussions with your lab partner.
- Communicate clearly and unambiguously with your lab partner while working.
Important safety rules that everyone must follow are:
- You must never work alone. There must always be at least two people in the room.
- Never leave activated equipment unattended without approval from an instructor.
- If any accident occurs, you must immediately report it to an instructor.
How to do well
This course is quite different from most of your past classes.
Skills that you have honed in past coursework may not apply, and you will need a completely different skill set.
For some of you, these may come as naturally as algebra. For others, they might take a while to develop.
Learning those skills is a primary goal of this class.
Here is my advice on how to approach things.
- Accept that you are confused. Identify what you don't understand.
This part never changes. If you know what you are doing, it is just an exercise, not research.
- Formulate a set of specific questions.
Pick some questions for which you think you know the answer, and confirm that.
Pick some questions for which you can find an answer.
- Plan a method for answering at least one of these questions.
- Carry out your plan.
- Go back to 1.
This approach works to attack problems of any scale.
You can use it to understand a completely new physical phenomenon or to debug why your car won't start.
Note that this is just a rephrasing of the scientific method.
It works for things that are not always recognized as science,
such as figuring out the behavior of financial markets or people--including yourself.
The methods you use to answer questions will not just be experimental.
You will need to do substantial reading on your own to understand the
theoretical issues underlying your experiments and how your equipment works.
We have equipment manuals and a small library of books that you may check out;
they must be returned by your next lab period.
You should do such reading before you begin your labs.
From it, you should develop a plan of action before you begin.
Careful preparation is important because you won't have much time to work with the equipment.
(This is true in most experimental work, e.g., when using shared equipment like a telescope.)
An important part of being prepared is understanding how your equipment works.
Before using it, you should plan to fiddle around to learn about it.
I encourage fiddling, but be careful not to break things.
The best way to avoid that is to read the manuals beforehand and plan your fiddling.
If the equipment is not working, or if you break it, notify an instructor promptly.
You will not get in trouble for breaking something, but you will be in trouble if you don't tell us about it.
Since time with the equipment is limited, you should carefully document everything that you do.
You might not expect something to depend on the temperature or the time of day,
but you should still record both. It could be helpful after you have collected all your data.
For example, you might find that one particular set of data is completely inconsistent with the rest.
By knowing when that data was recorded you can correlate it with other effects;
perhaps someone powered on some other equipment that caused interference.
It is also useful to analyse the data as you take it. This can help you quickly identify problems.
For example, if you are measuring voltage vs current,
you should make a table in your logbook where each row is one measurement and has columns for:
the time of the measurement, the voltage, the current, and any relevant comments.
Then, as you are filling in the table you should also plot the data, e.g., on the opposite page of your logbook.
Your plot might reveal a trend that can inform your subsequent work,
such as helping you decide to use larger or smaller voltage steps to
either go faster or with finer steps.
It will help your experiments succeed if you prepare well, clearly write down your plan,
and fully document your work as you go. This is also what we will look for while grading your logbooks.