2012

Instructors

Professor: Tobias Marriage (marriage@pha.jhu.edu), Office: Bloomberg 215

TAs: Christopher Brust (cbrust@pha.jhu.edu), Sean Cantrell (seancan@pha.jhu.edu)

Lab Guru: Steve Wonnell (wonnell@pha.jhu.edu)

Wiki

You'll need a wiki login to sign up for groups and labs. Also you are welcome to augment the experiment wiki pages with additional links/comments etc. To get a wiki login: Click "log in" at the top right and then click "request one". You'll need to fill out a form and then administrators authorize your use (if they so choose).

General Description

Welcome to the Advanced Physics Lab. In this class, you will carry out six experiments, some of which helped form the basis for modern physics. More importantly, you'll learn

• how to conduct an experiment with special attention to estimating systematic and statistical measurement errors,
• how to model the data/understand the goodness of fit (<math>\chi^2 </math>) and errors on model parameters,
• and how to present your work through scientific writing.

These three aspects essentially define the course. Each lab will be evaluated based on how well the three aspects are realized.

Groups

Labs are done in groups. In the first week students divide into 10 groups of 2-3 students each. Sign onto the wiki and add your names to the groups list.

Schedule

Lab times: Mondays 10:00-12:50, 13:30-16:20. You may come to either (or both) class periods. This is essentially when the professor and TAs will be available (note both TAs will not be present at both sessions). Each lab takes two weeks and therefore has two associated lab periods.

First Lab Period. Before the first lab period you should write an overview of the experiment and the procedure (essentially a draft of the introduction and the experiment sections of your report). Bring this to the lab to discuss the experiment with the professor and/or the TAs (Also they will "check off" your progress as part of the participation grade). In the first lab period you also take a first pass at experiment and data taking.

Second Lab Period. The next week you should have an initial analysis done of your data. You should bring a draft of your report with an initial data analysis section and any preliminary discussion. You should come to the lab in order to discuss your results with the professor and/or TAs.

The semester goes as follows. Unless noted otherwise below, final drafts of lab reports are due at midnight the day before the next lab begins.

Jan 30: Welcome Lecture

Feb 06: First Lab Begins

Feb 13: Latex Tutorial

Feb 20: Second Lab Begins

Mar 05: Third Lab Begins (Mar 19-23 is Spring Break)

Mar 26: Fourth Lab Begins

Apr 09: Fifth Lab Begins

Apr 23: Sixth Lab Begins (Due the day after reading period)

Labs

Responsibility for assistance and grading of labs will be split between the professor and TAs.

The labs are done in groups according to the following schedule:

Schedule 2012

Safety

Use your common sense in all situations. In these labs you'll encounter high magnetic fields (don't handle ferrous metals near them), weak radioactive materials (respect them), lasers (where protective eye wear -- provided), high temperatures (don't touch them) and other manageable hazards. When in doubt: ask the professor, Steve Wonnell or a TA.

Grading

Grades breakdown as

• 80% Labs
• 20% Preparation (bring in drafts as described in Schedule)

Each lab grade will be divided into three equal sections: experiment execution (20 pts), data analysis (20 pts), and presentation (20 pts).

Collaboration Policy

Execution of the experiment is a group effort, so is necessarily collaborative. Furthermore, students are encouraged to discuss experiments, analysis, and other course related issues with their peers (and, of course, with the instructors). However, each person should carry out their own data analysis (e.g., no code sharing), produce their own plots, and write their own report. Violations of academic ethics (e.g., plagiarism) will be handled according to JHU Policy.

Work Submission and Late Reports

We'll utilize Dropbox (www.dropbox.com) for submission of reports: each student will have a private dropbox by which to upload course materials for submission (and by which we can share files with you). If the dropbox fails, work may be emailed in PDF format to the instructor at marriage@pha.jhu.edu.

The reports are due by midnight on the day before the next lab begins. Sometimes, circumstances are such that one cannot get a report in on time (illness, grad school visits, etc). For this reason, each student is allowed one late report, which may be up to one week late. Use this wisely! After the first instance, a late report will result in having the awarded point total multiplied by 0.5. For example, an 88% score would become a 44% score.

All reports will be returned through dropbox as soon as possible and no later than 2 weeks from the submission due date. If you are missing a report evaluation, then notify the professor immediately.

Anatomy of an Experiment

This is an overview -- more detailed discussion will take place in tutorials.

Experiment Execution. The first step in executing an experiment is to have a good idea of the phenomenon being measured -- the reason why you're doing the experiment. Then you need to have a thorough knowledge of the experimental apparatus. With this preparation you will be able to take data. But obtaining measured values is not enough. You need both values and errors. You need to conduct the experiment in a way that estimates systematic errors and statistical errors. Systematic errors can be checked for by conducting the experiment in more than one way that should, e.g., give the same result and checking for discrepancies. Statistical errors may be obtained by repeating the experiment and evaluating the sample variance of the data or there might be an analytic expectation for the statistical error, as in the case of counting experiments.

Data Analysis and Interpretation. The input to data analysis consists of measured values and their errors. You then fit this data with some physical model. If the fit is "good", then you can believe the best-fit model parameters and associated model parameter errors. These model parameters tell you something about the physical world.

Presentation Lab reports constitute the language of the course. The sections of a report are

• Abstract -- Summarily say the aim of the experiment and what you used to measure the phenomenon. Then quote your result which is usually some physical parameter with errors.
• Introduction -- Describe the phenomenon being measured and any historical info
• Experiment Description -- Describe the experiment setup and procedure, including apparatus etc.
• Data Analysis -- Describe the model that you
• Discussion -- Interpret your results and discuss what may have gone wrong

Lab Report Specifications

The reports are to be created on a computer with computer generated graphics, plots, etc. The document preparation system for the reports is LaTeX. The computers in the PUC lab have various installations of LaTeX editors/compilers. You can also download freeware for your personal computers. The lab reports should have an abstract, an introduction, description of the experiment (apparatus and procedure), description of the analysis, discussion of results, a conclusion (including future directions), and a bibliography.

A standard strategy is to create your figures first in order to guide the body of the text.

Useful Texts

Data Analysis

• Bevington & Robinson, Data Reduction and Error Analysis for the Physical Sciences
• Press, Teukolsky, Vetterling, Flannery, Numerical Recipes in C (Available online)
• Lupton, "Statistics in Theory and Practice"

Latex

• Lamport, LaTeX: A Document Preparation System
• A Not Too Short Introduction to LaTeX: media:not_too_short.pdf

You might also find useful websites from previous years.