Physics III Lab

Spring Term 2014

General Information

Instructor:    Galen C. Duree Jr., PhD

Office:    Room DL102                       Phone:    872-6025                                 Box:    182


Office Hours:      9:00 AM - 9:30 AM  M T Th F  &  4:20 PM - 5:30 PM M T  Th F

The last lab experiments, entitled "Interference of Light from Two Slits", the write-up for which begins on page 5-23 in the lab manual, were conducted in CL117 this week, on Tuesday, May 13, 2014.

The lab reports are due in the green bin outside my office by 5:30 PM on May 23, 2014.

For this lab, you have two tasks.  (1) Using the He-Ne laser, determine the slit spacing between two different pairs of slits.  (2) Determine the wavelength of a diode laser using the two slit pairs that you measured with the He-Ne laser.  In order to do this, you will be using Logger Pro to record intensity vs. position.  Make sure that you perform at least two different trials (so you will have two separate files containing your data from Logger Pro) for each slit pair.  Measure the spacing between adjacent bright fringes using the "Analyze" and "Interpolate" functions in Logger Pro.  For each spacing measurement, determine the d value (part 1) or the wavelength (part 2).  Then average all of the d values or wavelength values for a given slit pair together and calculate the standard deviation.  These will be the values that you will report to fulfill the task requirements.  Do NOT calculate the average fringe spacing unless you want to propagate the uncertainty to get the d or wavelength value.  You will get a low report grade if the uncertainties are not calculated correctly and, unfortunately, there will be no time for you to redo the calculations!

Include at least one graph from each of the experiments (one for each laser/slit set), so there should be a minimum of 4 graphs included in your lab report.  However, it may be just as easy to include all 8 so that you have a record of all of the bright fringe locations when you do the analysis.

After this lab (and you turn in your report!), you are done for the year!!

Lab Report Format

A complete lab report must have the following sections:

Make sure that you address the specific tasks that I give you!  If you perform great analysis and have insightful conclusions, but do not address the tasks that I give you, do NOT expect a very good grade on your report - no matter how much effort you put into it!

Do not forget to update your Table of Contents and to number the pages in your lab notebook!

The first page of your report must have a title, the name of the P.I. (explicitly indicate who was the P.I.), the name of the lab assistant, and the date that the report was turned in (not the date that you performed the experiment!).

*Abstract - a BRIEF description of what you were investigating, how you conducted the experiment and your conclusions based on your experience.  Try to write the abstract with 150 words or less, but still communicate important information.  The abstract should not be a discussion of what you are going to do in the lab.  The abstract cannot be written before you have analyzed your data.  In the lab notebook, skip a page or two so that you can write this in at the beginning of the report after you have analyzed your data.

Introduction - a discussion about any details that you think would help someone perform the experiment.  This should include a discussion about the model or the method selected for performing the tests.  If you use models (equations) in your analysis, list the models in this section and describe what each of the variables represent.  Do NOT include formulas for calculating averages and standard deviations.

*Procedure - a detailed description of what you did in the lab.  At the beginning of this section, place the date and the time that you began the experiment.  This section must include a schematic, detailing how things were connected, where appropriate.  The raw data must appear in this section immediately following the description about how the data was taken.   A person must be able to read your procedure section and be able to duplicate your results without having the lab manual present.  Do not do any calculations in this section, just record how you performed the experiments and record the raw data.  If the data is taken by computer, you must specify the path and filename where the data is stored.   This information must be listed in this section right after the description of how the data was taken.  Do not simply list all of the files generated at the end of the section.

This section MUST be signed by the instructor before you leave the lab.  If you turn in a report without the signature, it will not be accepted!

Analysis - a sample of the calculations made in the lab.  **This section should include a sample of the error calculations and propagation of errors used in your analysis.   The final data that you are analyzing to generate conclusions, the values with appropriate uncertainties, must be shown in this section.  The actual calculations for each one does not have to be included, as long as you show an example for one, but you may include them all if you wish.  The calculations may be done by the computer, but include printouts of the worksheet in your lab book.  Any graphs or printouts that are placed in your notebook must occupy one whole page and be trimmed to fit within the page and not hang outside of the notebook.

*Conclusion - this section must have a conclusion that is based on your experiments and analysis.  If your conclusions do not following logically from your analysis, your grade will be deducted significantly.  This section must also contain a brief description of significant factors that you think affected your data, in particular, the uncertainties in your data (factors that contributed to the error in your experiment).  A good thing to keep in mind is to think of this report as a report you are submitting as part of your job responsibilities.   If you do not think your boss would accept what you have to say, it is a safe bet that I will not like it either.

The asterisks indicate the sections that I will pay closest attention to.

Modified May 15, 2014 by Galen C. Duree Jr.