Here we address advanced issues around lab reports, both formal and informal. This is a follow-up to the original Notes On Lab Reports which covers the basic structure of formal lab reports.
Basically, amateur hour is over. Consider the following notes on each section in lab reports.
The ABSTRACT contains One or Two paragraphs at most outlining what you did (the basic steps you went through to complete the experiment) and summarizing the results. Begin by stating why this was experiment done ("In this experiment the effect of pressure on a gaseous discharge in air is examined ..."). Next, state how it was done ("Using a vacuum system consisting of a turbomolecular pump ...") Finally state basic observations including any important numbers here such as key pressures ("at xxx.x torr the discharge was observed to be in the form of discs...") and measured spectral lines (just key ones since a table of twenty numbers is unsuitable for an abstract, something like "In the neon discharge a line at xxx.x nm was observed. This is not a neon line but rather was found to originate from nitrogen contamination in the tube ..."). Verbose abstracts with _too_ much information will be penalized marks.
The BACKGROUND consists of several pages summarizing specific theory and principles used in the lab. Include (1) basic configuration of equipment used, (2) the operating principles of anything unusual or special (e.g. a turbomolecular pump), and (3) explain any concepts required to understand the lab. Include expressions required for the prelab (If it was in the prelab, it was probably required to fully understand the experiment).
Diagrams of system components are required (e.g. a diagram of how a turbomolecular pump operates would be wise since a picture is worth 1000 words and no one wants to read a 1000 word description on how this pump works). Remember, though, that a picture without an explanation is useless. If you include a figure, REFER to it in the text that follows (that is the acid-test as to whether or not it is a useful diagram). Usually one decent figure paired with one decent paragraph is enough to explain a single concept as applied in a lab (although there may be several concepts worth discussing).
PROCEDURES explain what you actually did and the steps needed to perform the task. This should include enough detail to allow another person to duplicate the lab and obtain your results. Here you would NEVER include a cut-and-paste of this outline (unless your lab mark is too high and needs reduction) but would rather include a PROPERLY EDITED description of what you actually did. Avoid irrelevant details such as "I walked into the lab and took off my coat ...", "Our group consisted of three people, one turned the valves while the other picked his nose", or "We turned on the power switch as instructed by Mr. Csele" (I'm not kidding, I got that one once on a lab).
Literary diarrhea such as "We opened the needle valve by turning clockwise, it was a black valve with pretty blue labels, and we turned it until the gauge, which was a nice shade of red, began to increase ..." is completely unsuitable in a professional report ... instead try "Neon was admitted into the evacuated manifold using a needle valve until the pressure in the manifold was increased to xx.x torr as read on the Baratron gauge". See the difference in professionalism as well as pertinent details!). Before including a detail, ask yourself ... does the reader NEED to know this to reproduce the experiment? (The fact that the knob was black is irrelevant, I'm sure a green know would work just as well :). As well, specific details of 'what valve was turned when' are NOT required but rather a simple description such as "The manifold and tube were pumped to an ultimate pressure of xxx.xx torr then the manifold was sealed from the pump using the evacuate valve" or "a mercury spectrum tube was inserted into the power supply and a reference trace taken". It is likely that anyone in the world trying to reproduce this experiment would have similar, but not identical, equipment so details _too_ specific to this particular system are unnecessary. Another trap NOT to fall into is copying instructions from a text verbatim where they do NOT apply to this specific system (e.g. overzealous cut-and-paste).
Include relevant figures and numbers into the procedures (e.g. "The tube was pumped to 1.3*10-5 torr …", "A US-Lasers 808-5 diode laser operating at a measured wavelength of 806.6nm at a power output of 3.4mW was employed", or "20mA of drive current was used to excite the discharge"). Describe the figures you ACTUALLY used in the lab (as opposed to cutting-and-pasting the incorrect ones from a lab outline). Two or three pages should suffice since you would not mention every single step.
OBSERVATIONS detail what happened during the experiment and the results. Include drawings of observations if required to describe what you saw (and don't forget WORDS to describe the drawings - drawings of discs in a glass tube without words to go with it are a bit like inkblots and open to interpretation ... avoid this). Table of observed data (e.g. emission lines) are great however be sure to describe how they were observed/calculated (especially if the table has columns which represent the result of a particular computation such as error from a unknown) An example calculation showing the methodology for calculation is a must!
The CONCLUSIONS are usually a page or two summary explaining the observed results. Here you'd include a summary of observed results and quite possibly repeat (but in a very condensed and summarized form) some observations in order to illustate some effects (for example, you might include one drawing of observed 'discs' in a gas discharge to illustrate such an effect). Do not include a chart of observed spectral lines here but instead discuss where they came from (you might mention a few specific lines, but don't include an entire table again). In the case of a spectroscopy experiment with, say, neon gas you'd identify lines _NOT_ from neon here (anything blue and violet is definately not from neon) and postulate where they came from.
REFERENCES should not be on a separate page but rather as a footnote on each page. If you used a diagram from a reference in the background section quote the source as a footnote on that page. Similarly if you quoted that the red line of krypton gas has a known wavelength of 647.1nm, use a footnote to show the source of this figure (e.g. "Source - NIST eBook"). Marks will be deducted for numbers and figures without proper references.
... and keep lab reports in third-person, in terms of "... was done" or "the chamber was pumped" as opposed to "We pumped the chamber" or "My buddy sat on his butt watching us" ... keep personal opinions and descriptions out of lab reports.
Where a lab report asks you to answer questions, consider the following helpful hints:
Base answers on scientific fact, not colloquialisms. If one were to ask "Why is a dielectric filter better than a gel filter?" one could say "It isolates one colour better than others" but that is vague, and certainly not worth much as an explanation in terms of explaining why it is better (it is also not worth much in terms of marks!). Among other things, we never speak of 'colour' - in scientific terms always refer to wavelength. 'Colour' is a subjective thing, wavelength is something one cannot argue about (e.g. is the 488nm line of the argon laser blue or cyan? Regardless, one cannot argue about wavelength.
A better answer would be "dielectric filters offer a much more narrow spectral passband than gel filters which frequently allow wavelengths spanning hundreds of nanometers (FWHM) to pass. In contrast, even an inexpensive dielectric filter might feature a passband of less than 20nm." This is scientiic, and based on fact (or observations).
When a question is asked such as "why is a p-i-n diode best suited for this purpose" one is expected to research a p-i-n diode ("Googling" a manufacturer's website and examining datasheets is a good idea) to determine the characteristics for which it excels. One might mention that such detectors are fast (quoting speeds like "frequently, risetimes of such diodes are less than 20ns"). One could even contrast other detectors to point-out why these detectors are slower (or at least quote speeds of other types for comparison).
Many answers to questions from a particular lab might well be found in the SOPs and related manuals for equipment in the lab.
When a questions looks simple, such as "What is a monochromator ?", it probably requires more explanation than "a box tha separates colours"! The correct proedure to answer this question would be to describe what the thing does and how it does it. Again, "googling" a commercial manufacturer of such equipment will likely provide a wealth of information including optical arrangement (Ever hear of "Czerny-Turner"?? You should). If a lab has only seven questions, but counts as a full lab, one expects each question to have a decent and complete answer, not superficial.
Where a question says "Compare ..." the correct answer will likely present data from an experiment in the form of a table as well as a discussion (in WORDS) interpreting the data. If one was comparing, for example, the intensities of transitions between the 3p-3s and 5s-3p quantum systems, you'd start with a table of data then a paragraph describing the interpretation. The table of data might include the wavelength, precise levels involved (to attribute them properly to a quantum system), and both observed (raw) and normalized intensities. Where a normalization is undertaken, one must describe how it was done and the unity reference employed. As for discussion, comments like "In all cases, transitions in the 3p-3s system revealed higher overall intensities than those in the 5s-3p system however the presence of helium in the discharge was found to increase the intensity ...[yadda yadda] ... by and average 50%. The logical interpretation of these results suggests that helium provides a direct pathway to ... [yadda yadda] ... as described in Csele, in section 4.3"). One might even include a diagram from a reference (4.3.3 ?) showing how a particular effect works.
Condensed lab reports do not always have discrete sections, however essential observations and conclusios must be included where required.
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