How to Write a Good, if not Perfect Lab Notebook

Transcription

1 How to Write a Good, if not Perfect Lab Notebook Ashley Carter - Advanced Optics Lab Why are good lab notebooks important? A complete, legible, thorough lab notebook allows anyone to be able to perform the experiment you have done, even yourself! For example, Dave Samuels, a chemistry student who went to Japan for an internship at Sony, used his lab notebook to setup a Mach-Zender interferometer 1. With his background in chemistry he said that it would have been very difficult to setup that system without having the advanced optics lab. In such a case, it is essential that your lab notebooks contain all of the pertinent information about the experiment you have done. That way at a later date you or somebody else can easily reproduce your work. Furthermore, keeping a good lab notebook is a good habit to get into. If your actual lab notebook contains illegible experimental data or is incomplete then it will be hard to publish papers or patent devices. To prove this point I would like to relate two anecdotes about very bad notebooks. The first is about LeMonnier, a French astronomer that actually discovered the planet Uranus. His notebook was so incomplete that he concluded that Uranus was a comet, and instead someone else (Herschel) is credited with the discovery. The second is about Gordon Gould who did some interesting work on the uses of lasers when they were first being developed. Sadly, he had his notebook witnessed by a candy store notary and didn t document private communications. As a result he had several legal battles before he was awarded some of the credit for his work 2. The lesson of both stories is that good lab notebooks are important. How should I organize my lab notebook? The first thing that a good lab notebook should have is organization. There should be a table of contents on the first page with all of the labs/prelabs referenced. At the top of each lab/prelab should be the title of the experiment, the date, and the names of any collaborators. Then each section of the lab/prelab should have the question pasted in the notebook at the beginning of the section and should be followed by the experimental setup, data, results, and conclusions. Other variations are possible, but a reasonable organization of the lab notebook will allow the reader to scan to find the desired measurements. For each lab section (or new experiment) there should be an experimental diagram and procedure. First you should build the experiment for that section and verify that it works. If it does then you should draw a diagram of it. Label all of the distances and objects. Make sure that variable object parameters like focal lengths, pinhole sizes, magnifications, etc. are recorded. To make drawing the diagram easier you may want to develop a series of symbols for commonly used objects and just have a key. Other objects you can represent with a square and identifying initials. Please see Figure 1A for an example of a good experimental diagram. After the diagram you should write down any procedures or helpful hints that weren t in the lab question that you taped into your notebook. Don t assume anything is obvious, because usually it isn t.

2 After the experiment is built and diagramed you should relate the outcome. The outcome could be a picture, an observation, or a table of data points. A picture should be titled and labeled. Plus any generalities should be noted. See Figure 2 for a properly drawn picture. An observation should be clearly stated. Tables of data points should be labeled appropriately with the right units and titled. Also the error in the data should be noted. Finally, any outcome should be analyzed immediately after it was observed to make sure that you are seeing what you expect. Analysis may mean to draw a graph or calculate some value. For a graph make sure that there is a title, the axis are labeled properly, and the data points are shown as is the case in Figure 1C. For calculating a value, make sure that the calculation is referenced or clearly written in your lab notebook with all of the steps. Also make sure to solve in terms of variables and not plug in actual numbers until the end. After the graph or calculation be sure to note any errors that might have propagated through your measurement. Then box any value or observation that answers the questions asked by the lab. Lastly make sure to compare your answers to what you expect. Don t say that the answer is close, it is either within the error (and therefore what you expect) or not 3. If the answer is not what you expect you may need to do the section over, or at least explain what other errors could have caused the faulty measurement. Don t lie about your data to get an answer you think is correct. It is much better to be honest and relate what you saw. As long as someone can follow your lab notebook and produce the same result, then you are not wrong according to your procedure. How can I make my lab notebook better than good? Keeping a good lab notebook is easier if you have the right tools. A notebook with page numbers is a must. Quadrille ruled is also nice so that it is easier to draw pictures, tables, and graphs. A larger notebook with pages big enough so that 8.5 x11 pieces of paper can be taped into it is very convenient as well. Plus the notebook should be labeled with your name, phone number, address, or anything that would identify it as yours should it get lost. A pen must be used, not pencil. This will prevent smudging and any urge to erase. A ballpoint pen is usually the best, since felt tip pens tend to bleed or smear and can become very messy. Lab notebooks are much better if you do everything in the section at once. Sometimes you might want to put something off until the end, or do something at home. This is good in theory, but usually if you don t write anything down for a section, chances are you will remember less later. Plus as the lab progresses you will get more tired, so that putting things off until the end, becomes not doing things at all. Another reason is that sometimes lab sections build on each other so that if you don t have one section completed, it is harder to do the next section. The other way to improve your lab notebook is to ask the TA or professor questions. This especially helps if lab questions are open ended or aren t clear. The TA or professor can tell you what they were expecting when they wrote the question. However, make sure to write down any assumptions that you make about what the question is asking for later use. Plus, the TA or professor can tell you other exciting things to look for that might not be explicitly written in the lab question. Also, they can

3 give you hints for the best or fastest way to setup the experiment for each section. This can improve your results or at least increase the amount of time you are able to spend exploring. Probably the most beneficial advice is what to do if you make a mistake. If that happens then just cross through the mistake once so that it is still visible, and don t erase, white it out, or obliterate it. Mistakes are results too and you want to be able to look back and see that you made them 4. If you made an error and there is not enough room to fix it, then write down a reference to another page where there is enough room to fix the mistake. Also make sure that before the correction you note that it is a correction from whatever page, and that after the correction you write down that you are continuing from whatever page. Do not rip out, or add pages to fix mistakes, or in general 3. Remember what R. Coueto said, It is a notebook, not a neat book 2. You will make mistakes so that your lab notebook is not perfect, but these are to be expected and actually add more than they detract from the notebook. How do I keep a legible notebook? Although your lab notebook doesn t have to be pristine, it does have to be legible and reproducible, so some level of neatness is required. This is especially painful for people that are bad at drawings or handwriting. To correct bad drawings use a straight edge, protractor, or grid lines whenever possible. For bad handwriting write more and make your words bigger. If you write bigger, it is easier to see in general and letters are wider spaced for easier determination. If you don t use abbreviations or short phrases then it will be easier to determine the word from the context clues. Compare the three writing samples in Figure 3. Notice that the bigger and wordier samples are the easiest to read. For both of these problems and neater lab notebooks in general it helps if there is lots of white space. White space can be used to break up sections and also different parts within sections. Plus if things need to be added later, then there is always room to add them. A neat lab notebook is easily accomplished with the aid of computers. If there is a nearby computer that is able to print then it is much easier to have a neater notebook. Graphs can be plotted on a computer, printed out, and taped into the notebook. Oscilloscopes that have printers can print out a trace which can be taped into the notebook (make sure the tape doesn t cover any data because the ink on the trace may be dissolved where the tape is). The digital camera can take pictures of optical phenomenon which also can be printed and taped in. Plus, for students with really bad handwriting a section summary can be typed up quickly and pasted in for a neater notebook. However, this all depends on having a computer, oscilloscope, or digital camera that works. This is not always the case so depending on these devices is not a good idea. Awknowledgements The author would like to thank Marty Boyd for his input on how to overcome bad handwriting, as well as Bob McLeod, Carol Cogswell, and Ed McKenna for their evaluations of my labs. This paper was done as a part of the Advanced Optics Lab class at University of Colorado. Tuition was funded by OSEP.

4 1 private communiqué with Dave Samuels

5 Figure 1A: This is a lab notebook excerpt from the crystal optics lab where a student observes what happens when a half waveplate is rotated. Comments in red indicate good and bad observations about the lab notebook techniques. Setup contains measurements and a legend Good procedure for alignment of the setup

6 Figure 1B: Continuation of Figure 1. Don t scribble out just cross out once Show error in measurements Good to show calculations for columns in table Good to graph as you go so you know if data looks good, in this case the ½ waveplate was clipping so need to retake data

7 Figure 1C: Continuation of Figure 1. Now data looks better Always comment on trends of graphs and possible errors

8 Figure 1D: Continuation of Figure 1. Compare what you got to what you expect

9 Figure 2: This is an example of a good picture from an excerpt of a lab notebook on the crystal optics lab. The student draws very detailed pictures of what the output beam from a conscopic crystal setup looks like. The student titles and labels each drawing and provides measurements. In the text P2 refers to the second polarizer.

10 Figure 3: Example of bad hand writing from a lab notebook on the crystal optics lab. The student is trying to explain what limits the isolation of back reflections off of a mirror when two polarizers and a quarter waveplate are used to eliminate them. In the first paragraph the student writes too small and the text is illegible. In the second paragraph the text is still small, but the student writes more so that the reader can tell from context clues what is being said. In the third paragraph the student writes bigger so that the text becomes legible.