PHYSICS 444W/544: ADVANCED LABORATORY

Fall 2017

Jed Brody and Horace Dale

The purpose of this course is to broaden and refine your laboratory and analytical skills, to further your mastery of several fields of physics, and to communicate your results in written reports that are clear, concise, and complete. You will choose four of fifteen available projects, grouped by topic:

QUANTUM ENTANGLEMENT!!!

Quantum entanglement:  Shine violet light through a beta barium borate crystal to create pairs of entangled infrared photons, and demonstrate a violation of a Bell inequality.  This apparatus was funded in part by a grant from the Reichert Foundation.  

COMPUTER INTERFACING

Spectrometer interfaced with Arduino: Write a Python script to control a spectrometer interfaced with an Arduino microcontroller. Wow!

LabVIEW: Acquire basic proficiency in sophisticated interfacing software used in many research labs.  Record the IV curve of a diode, and derive the ideal diode equation.

ANALOG ELECTRONICS

Transistors: Study the properties and applications of bipolar junction transistors. Construct emitter followers, amplifiers, and a current source.

Op amps: Study the applications and limitations of op amps. Construct amplifiers, differentiator and integrator circuits, and a current source.

Chaos in electronics: Construct circuits that exhibit the Lorenz attractor and other chaotic phenomena. Prerequisite: op amps, either in this course or previously.

SOLID-STATE PHYSICS

Transient heat conduction: Use laser beam-bending to measure and analyze the "cold front" passing through a material dipped in ice water.

Hall effect: Fabricate silicon and copper Hall devices and measure Hall voltage and carrier density and type. Optional: if you do transistors or op amps before Hall effect, you can build your current source yourself!

LED statistical mechanics: Observe the Boltzmann distribution in LED emission spectra. Optional: if you do transistors or op amps before LEDs, you can build your current source yourself! And if you also choose Hall effect, do Hall effect before LEDs.

CLASSICAL MECHANICS

Rotary pendulum: Observe natural frequency, damped oscillations, resonance response, period doubling, and chaotic attractors in the motion of a rotary pendulum.

Collisions: Construct a digital circuit to determine the durations of collisions between metal spheres and a plate.

Water-column oscillations: Predict and measure the frequencies of oscillating water columns.

ASTRONOMY

Pulsating variables: Observe and analyze the light curves of variable stars.

Eclipsing Binaries: Observe and analyze the light curves of eclipsing binaries.

Exoplanets: Join the search for planets around other stars.

You will write lab reports for three of your four projects. Electronic submissions are welcome.

Since the refinement of written communication is a major goal of this course, you will have the opportunity to rewrite each lab report. The grade for the revised report will replace the original grade only if the new grade is higher, so you have nothing to lose.

Grades are determined as follows:

90 points Three lab reports (30 points each).

10 points Completion of the project that you don't write a report about.  (Show me the raw data.)

For safety, please do not wear open-toe shoes in the lab. Liquid nitrogen is used in some of the experiments.

Please do not hesitate to contact us if you'd like help understanding any experimental principles or procedures. That's why we're here.

Jed Brody

N308, 7-5580

jbrody@emory.edu

Horace Dale

N218, 7-4007

hdale@emory.edu

Statement from the Department of Physics:  We are all here in this class for the same reason:  to learn physics.  It is unacceptable to judge your fellow students by gender, race, or anything else.  Please treat your classmates with respect both in and out of the classroom.  If you have any concerns please talk with the teacher or the department chair, Prof. Eric Weeks.

INTRODUCTION

August 23. Project overview. Electronics tutorial (part 1).

August 28. Project selection. Electronics tutorial (part 2).

PROJECT 1

August 30

September 6

September 11

September 13

September 18

PROJECT 2

September 20.  Lab report 1 due.

September 25

September 27.  Lab report 1 returned.

October 2

October 4.  Lab report 1 (revised) due.  

October 11

PROJECT 3

October 16. Lab report 2 due.

October 18

October 23. Lab report 2 returned.

October 25

October 30. Lab report 2 (revised) due.

November 2

PROJECT 4

November 1. Lab report 3 due.

November 8

November 13. Lab report 3 returned.

November 15

November 20. Lab report 3 (revised) due

November 27 

CONCLUSION

November 29. Lab report 4 due. Course evaluations.

December 4. Lab report 4 returned in individual conferences.

December 7. Lab report 4 (revised) due.

Guidelines for Writing Lab Reports

Your lab report should be clearly written and correct. It will probably consist of five or six sections.

1. The abstract is a single short paragraph that summarizes the report. It gives the main objectives and conclusions of the experiment. Specific, quantitative results must be included. Many readers of scientific papers read only the abstracts and the figure captions before deciding whether the whole paper is worth reading. The abstract is sometimes in the present tense, never the future tense. I've often written my abstract by copying the conclusion section, rephrasing it a little, and adding an introductory sentence in front.

2. Introduction. This section introduces all the theory that the reader will need to understand the subsequent sections. Any equations that you'll use are given here with qualitative descriptions. Define all variables! If you like, you may briefly discuss the historical background and importance of the experiment.

3. Procedure. This section contains a description of the experimental process. In principle, someone should be able to reproduce your experiment after reading this section. The procedure, unlike the lab manual, is always in first or third person, never second person. (Incorrect: Turn on the laser. Correct: We turned on the laser. Correct but less clear: The laser was turned on.)

4. Results. This section is for your experimental data tables and all other unprocessed data collected during the experiment. (The text must refer to every table and figure. Example: "Figure 1 shows….") I tend to combine this section with the subsequent section and call it "Results and discussion."

5. Analysis and discussion. In this section, the theory from the introduction is applied to your own data. Manipulation of the data from the results section is presented here. Graphs showing functional relationships among experimental parameters are usually the best way to present your findings. It is frequently desirable to show theoretical curves and experimental data values on the same plot.

6. Conclusion. What do you want the reader to remember about your report? What results or insights are you proud of? How can you clearly and concisely summarize what you've learned? If appropriate, comment on the limitations of your findings, or suggest future work.

Your lab report will be graded with the following in mind:

Understanding: Do you correctly explain the physics underlying the experiment?

Completeness: Have you left out anything?

Clarity: Is your report clear and to the point? Define variables as you introduce them. Remember that units are very important. Include units in the axis labels of graphs and the headings of tables.

Ambiguity: This is very important! Think about ambiguity, and avoid it. Examples:

· "Inadequately focused, we could not see anything with the microscope." In this sentence, what (or who?) was inadequately focused?

· "In free space, he came up with a value of c = 2.99796 * 10⁸ m/s." In this sentence (from an actual lab report!), who (or what) is in free space?

Both examples illustrate the common error of a misplaced modifier.

Poets want every word to mean as many things as possible; science writers want exactly the opposite. Every single sentence in your report should have only one possible interpretation.

Significant digits: Be reasonable. Do not show ten significant digits in your results unless there are ten significant digits in your raw data.

Uncertainties and error propagation: This is a sophisticated subject. Here's a useful overview:  http://www.physics.umd.edu/courses/Phys261/F06/ErrorPropagation.pdf.

Captions: Figure captions go below the figure. Table captions go above the table. (This is an arbitrary but universal rule; check any journal.) Only the first letter of each sentence is capitalized. The first sentence in a caption is typically a fragment, as in “Figure 1. The apparatus.” Subsequent sentences, if there are any, are complete sentences.

Equations: Even sentences containing equations should be punctuated normally. Avoid sentence fragments. The format for equations is as follows:

We now will study the beloved Pythagorean Theorem,

a² + b² = c². (1)

Equation (1) shows.... (Notice the period in the previous line!)

Spelling and grammar: Proofread.

Most common grammatical error: Run-on sentences (specifically, comma splices, which are common in informal writing but inappropriate in scientific papers).

INCORRECT: I love writing lab reports, I weep at the beauty of my work.

CORRECT: I love writing lab reports; I weep at the beauty of my work.

CORRECT: I love writing lab reports, and I weep at the beauty of my work.

CORRECT: I love writing lab reports. I weep at the beauty of my work.

Another common grammatical error: Not knowing the difference between "its" and "it's."

Accommodate your reader: Good scientific papers accommodate both the "lazy reader" and the "thorough reader":

• The "lazy reader" reads only the abstract and the figure captions. All the evidence that you've accomplished something interesting should appear in the abstract, figures, and figure captions. The abstract should stand on its own and make sense to someone who hasn't read the rest of the paper. Each figure with its caption should similarly make sense to someone who hasn't read the rest of the paper.
• The "thorough reader" (possibly a "lazy reader" impressed by your abstract and figures) wants to read a continuous narrative from start to finish. This reader will ignore your figures and tables until the text refers to them; you should guide your reader to each figure and table whenever you want your reader to look there.

Plagiarism: Plagiarism is a violation of the Emory Honor Code. You are expected to write your laboratory reports on your own. Any unique phrases lifted directly from any source, including the internet, must be enclosed in quotation marks with the source clearly identified. All sources that you studied to gain understanding while preparing to write your laboratory report, including links to the internet, should be listed at the end of your report under References. If you are ever in doubt, identify the source of your material. In particular, be sure to cite the source of any graphics you download into your report.  I don't like to be bossy, but I'd like to help you avoid the mistakes made by former students.  Therefore, just to be helpful, I'm providing a list of things that you may not do:

• You may not copy entire paragraphs from any source.  In physics papers, we almost never quote exact text.
• You and your lab partner may jointly generate figures and tables, but you may not jointly produce text.  You may not write a single report and then do a sentence-by-sentence paraphrase to generate a "second report."
• You may not do a sentence-by-sentence paraphrase of any document.  I know it's hard to come up with a unique explanation of a technical topic, but the idea is to understand it well enough to pull the sentences "out of your head" (or your notes).
• You may not use anyone else's data in lieu of data you're suppose to record yourself.  You may, however, cite anyone else's data for purposes of discussion.
• If you don't even show up in lab, you may not use your lab partner's data.  Equivalently, you may not share your data with a so-called lab partner who doesn't even show up in lab.