Research Guides: Modern Physics: PHYS 2796: Lab Reports

Lab Report Template

PHY 2796 Modern Physics Laboratory (provide an informative title)

Your name, Department of Physics, Temple University

Abstract
This paper describes the required format of the lab reports of the experiments performed in PHYSICS 2796 Modern Physics Laboratory. It also serves as a template for your lab reports. An abstract is designed to give the reader: a) Knowledge of the general method employed, perhaps in one or two sentences. b) Results of the main measurements, including values and errors. c) Relation to other measurements. d) Relation to a theoretical prediction. Typically you write the abstract last. The margins for the report should be 1 inch (2.5 cm) all the way around. Use double spacing and 12 point fonts.

Introduction
Each experiment you will perform in this course played a very important role in shaping current-day physics. Your introduction should describe the thinking of the physics community before this experiment was carried out. That should involve doing some research at the library and with various textbooks. As such, information from a source should be referenced [1]. Place the references at the end of the paper and use proper technique. Websites are not accepted because they are not refereed or reliable. Likewise, you should also research and introduce the reader to the person or persons credited with carrying out the experiment. Sometimes this will be easy, for example the discovery of the electron. Sometimes this will be more difficult, for example the radioactive half-life experiment. We are not interested in trivial facts such as their birthdates and hometowns, but important information like their apparatus and its shortcomings. A well-research report will greatly improve your score.

Experimental Method
   A description of the experiment you carried out. The experimental setup should not be a recipe, but a set of text that describes all the various pieces of equipment used, their arrangements, any calibrations, any settings, how the data was collected, and other information deemed necessary for the reader to understand what is going on.
   A picture is necessary in all cases. Drawing such figures with a drawing program is required. Failure to do so will affect your grade. All word processing programs now include some sort of drawing tool. A good digital picture will also satisfy this requirement. Every student should create their own figures. Reference the figure as “Figure 1” and attach it and all the other figures at the end of the report. Each figure should have a title. If you would like to electronically paste the figures right into the text, you may do so as long as it looks good. Note, a figure inserted into the text should appear before it is referenced in the text. Leave some space between the figure and the text to set it apart. Typically figures in text are placed at the top of the page.
   Most of this section and the introduction can be completed BEFORE you actually do the experiment. Preparing for the experiment by reading the lab scripts and lab manuals is vital to successfully completing the experiments!

Theoretical Background
In this section you should derive the equations you will use to analyze your results. The derivation should start from some well-known physics equation and work to a final result. Each equation should be numbered and can be referred to by number. Try not to skip too many steps, but basic algebraic rearrangements can be skipped. A figure may be necessary. The lab script includes some of these and you can use them and fill in some of the gaps. The equations will look the best if you use an equation editor. Hand written equations are NOT acceptable.

   Figure 1 shows a block moving down an incline and the free body diagram associated with the block. The block has a mass m. The normal force FN, the force due to friction fk = mk FN, where mk is the coefficient of kinetic friction between the block and the ramp, and the weight of the block mg are shown. The ramp is inclined at an angle q. Notice the description of the figure in the text. The figure has just a simple caption/title and the text then explains it. Note the use of italics for all variables and the symbol font.
   The motion of the block of mass m moving on an incline can be described beginning with Newton’s Second law.
   Do not go overboard with the derivation. Short, concise and to the point is much more effective. Note that all equations should be numbered!

Results and Analysis
This section shows your data. The lab report should include data tables. Data tables can be created by your word processor and referenced as Table 1. Graphs must be referred to as Figures. Graphs must be plotted using graphing software (Excel, Mathematica, MathLab…). Hand-draw graphs are not acceptable. Theory lines (as derived in the earlier section) and data points must be separated. Data points should never be connected by lines unless you have collected a lot of data. A best-fit line (draw using data analysis tools) is necessary to correctly analyze the data. Using solid lines versus dashed lines works great to separate theory and experiment. You must have a legend. Sources of error should be identified and the consequences on the results carried through. Constants should not be sources of error. Human error is not acceptable.
It is the imperative that every final experimental result (and intermediate results, if appropriate) must be quoted with units and the experimental uncertainty. You are expected to use the techniques of estimating and reporting uncertainties in measurements as presented in the class discussion on error analysis. Your laboratory instructor will return your report ungraded if it is deficient in this regard.

Conclusions
The conclusion is a general summary of the experiment. What were the historical and science consequences of this experiment? How has physics changed because of this experiment? The lab report should be 5-7 pages in length without figures and tables. The course syllabus shows the order laboratory experiments will be carried out and the due dates of the laboratory reports. Late reports will not be accepted. Handing in something is better than nothing. The draft for each report is due on Tuesday of the following week after the experiment is performed. The more complete the draft the more comments can be made to the draft and the more refined will be the final copy. A draft will be graded out of 20 points and the final report will be graded out of the remaining 80 points, so it is really imperative that you complete the draft on time and that it is done as well as can be.
The lab script and relevant lab manuals for each experiment will be posted on BB course site. You should download the lab script the week before you will do the experiment. You should not rush through the experiments. Damaging the equipment is not acceptable. Please ask for help. Always set knobs to zero before turning the equipment off and on. These experiments should be fairly precise, so huge percent errors means you made a mistake. Teaching assistant will be available in the lab during regular class time all semester.

References
[1] Use Physical Review reference notation. In the second week of the course an information literacy session is scheduled to introduce you to information sources and research skills. You will need these skills for the remainder of your scientific career, especially as a teacher!

Things to Avoid in Your Reports

Vagueness: All language should be precise. Avoid words like “approximately,”“sort of,” et cetera. You can lose points by simply making unsubstantiated or uninformative statements. Never attribute uncertainties to nondescript causes like “experimental error” or “equipment error” or that standby of pre-med physics labs, “human error.” Statements like these will instantly cause your report to be marked down.
Nonscientific conclusions: You should report precisely worded scientific conclusions, i.e. “We found the mass of an electron to be 0.532 ± 0.019 MeV/c2” or “We verified the hypothesis that electric charge is quantized.” Do not include opinions (“This lab was great,” “This was a hard lab”). Do not include personal statements such as “We learned about the Hall effect.”
Blaming the equipment: Your task is to produce the best measurement possible given the equipment available. The limitations of the equipment should be treated scientifically, as terms in your uncertainty calculation. Do not use any section of the report for venting or complaining! A statement that, say, “the calibration of the galvanometer limits the precision of this measurement” is good; a statement that “this galvanometer should be replaced” or “We had to use a crummy galvanometer” is bad. (Note that this doesn’t mean you should shy away from commenting on how an experiment could be improved.)
Confusion between “error” and “discrepancy:” When you compare your results with their related “accepted” values, be aware that the word “discrepancy” has a meaning different from “error.” In physics, “error” is generally a synonym for “uncertainty.” It’s purely a function of how precise your equipment and analysis are, not the answer you got or how far it is from the textbook value.
Ungrammatical English: You’re expected to learn how to write professional reports. Good language is a critical aspect of this.
Second-person writing: Do not write the procedure as a list of commands: you are writing a report, not a manual. The procedure should be a past-tense, first-person narrative of what you did.
Excessive computer output: Excel can easily perform a repetitive calculation on a large set of data and report all the individual steps for each data point. This is completely useless and renders a lab report unreadable. You should give a detailed explanation of the basic calculation for a single data point, then give the result in compact table form for all the data points.