INTRODUCTION
DOING THE LAB
YOUR LAB NOTEBOOK
DEADLINES
The labs in the Waves course will give you the opportunity to observe wave phenomena, deepen your physical insight, and sharpen your experimental physics skills. This document is intended both to provide some administrative information and to offer some advice that I hope will improve the quality and efficiency of your lab work. As you do the labs, keep in mind that physics is supposed to be fun (that's the primary reason for the existence of physicists).
In many cases there is some preliminary work that can be done before you arrive in the lab. The better prepared you are, the more smoothly and quickly the lab is likely to go.
Although you will frequently find that you will need more than just your allotted lab time to do a good job, you should resist the temptation to "take the data now and figure it out later." There are several reasons for this. First, you need to see your experimental results while you are doing the experiment so you can be sure that things are OK. You don't want to find out later that you spent all that time taking data that make no sense. Second, if you do discover something wrong with your results, you want to be able to find out what happened and fix it. Even if you return to the lab, the apparatus may well have been altered in a way that would make it impossible to track down a problem, such as an incorrect meter scale, that would be easy to catch while you were still doing the experiment. Third, since these experiments are supposed to be learning experiences, you should try as much as possible to integrate your doing of the experiment with your thinking about it. Finally, I'm more readily available to you while you're in lab and can help you with any problems that arise.
Your lab notebook should contain a clear record of what you did for each experiment. Ideally, it should be a real-time log of your work, although in practice you may add some explanatory material and data analysis later. In any case, it should look like a real-time record in the sense that the description of the experiment and the apparatus precedes the data, and so on. In no cases should you record data, with the possible exception of "trial runs," anywhere other than in your notebook. The record in your notebook should be self-contained and should not rely on the lab notes for completeness. Explain what you are doing in words; don't just write down pages of numbers and equations. Your notebook must be clear and complete enough for someone else to be able to reproduce your experiment by reading it. Each member of a lab group should have a complete set of data; do not refer to information in your partner's book. Photocopying of unique items is acceptable.
Try to record data in a logical way and include the relevant units and a description of what was being measured and how it was measured. Neatness is worth striving for. You should also pay attention to the uncertainties involved in your measurements. As you know, numerical results should not be quoted with more digits than are justified by the uncertainties in the measurement or calculation. At the other extreme, try to avoid using terms such as "large" unless the basis of comparison is very clear; try to use numerical values instead. If the data don't look right, try to find out why.
Use graphs liberally--a picture is indeed worth a thousand words. It is your choice whether to draw the graphs by hand or to use a computer; do whatever is more efficient for you. Several Macintosh computers are available in the waves lab for your use.
Many of the labs involve electronic equipment. In such cases your notebook should include a fairly detailed interconnection diagram, with connectors labeled and settings recorded. You should be able to put the experiment together based on your lab notes. If oscilloscope observations are involved, sketch the waveforms (with scales indicated) in your notebook.
In most cases you will be comparing your experimental results with some sort of theoretical prediction. You do not need to include derivations of theoretical results in your notebook, but you should show any calculations based on theory that you want to compare with your experimental results. Try to make the comparison between theory and experiment as clear as possible; plot both on the same graph, if appropriate, or make a table so the theoretical and experimental results can be easily compared. You should also compare the difference between the two sets of results with the uncertainties in each and think about whether the agreement is realistic.
You should use one of the large, brown notebooks as your lab book. Please use a pen when writing in your notebook. If you make an error, just draw a single line through the offending words or numbers; do not obliterate them because you may discover later that what you thought was an error was actually something significant in the data. Any graphs or other separate sheets of paper that you wish to include in your notebook should be taped or stapled securely to the notebook pages. I would prefer that you not keep the lab notes in your notebook.
Throughout your lab work keep the purpose of the experiment in mind. (By "purpose" I mean the scientific, not the educational, objective.) This purpose should be spelled out at the very beginning of your writeup, and should reappear in the conclusions that you draw at the end. The conclusion is perhaps the most important part of your lab write-up, for it is there that you must explain what your experiment meant. Do not simply summarize your experiment--tell what you have shown. Answer questions like the following. Have you verified any physical laws? If you measured a physical quantity, how well does that number agree with the literature value? What is the dominant source of error in the experiment? How could the experiment be improved the next time it is done? What is the logical next step?
The labs for this course continue to evolve, and your suggestions for improvements are always welcome. In addition, if you have an idea for an experiment that you would like to do in place of one of the standard experiments, talk with me about it and I'll see if we can work something out.
Notebooks are due Friday at 3 pm. You may give your notebook to me in person, leave it in the waves lab on the blue round table, or slide it under my office door if the door is closed. I will put your notebooks in the waves lab when they have been graded. Grades will be assigned on an A-F scale
A Completion of work beyond the requirements of the lab.
B A good basic job
C Noteworthy shortcomings
D Lab done, but quality very poor
F Not present or no report
Last Updated on 1/20/99