As in any essay, typos can often be encountered in a lab report. Some can be innocent (e.g. misspelling) and ignored; in the end what matters is the scientific understanding and interpretation of the results. But what happens when a little typo can completely alter the experimental outcome as well as shake the confidence of whether the author does understand what they are talking about, and not copy-pasting numbers and graphs?
Below I am listing three of the most extravagant examples of lab report "typos" that made me cry like Phoebe:
1. How long can a Fresnel diffraction pattern be?
Fresnel diffraction is observed when a spherical wavefront reaches a diffracting object such as a slit. Typically in a Physics lab, this experiment can be done with the use of a laser, an objective or other strong diverging lens, a slit (preferably that can be varied to observe patterns for various slit widths) and a detector to scan the pattern and record the light intensity changes. Brilliant. And since we are talking about the average lab environment, the optical bench is expected to be 1 meter or so and hence the beam's divergence (applying basic trigonometry) should cause overall a diffracting pattern of a few cm long. So far, so good. But to be fair, you don't even need to do the calculations and estimate the size of your pattern, your light source is in the visual spectrum and hence by placing a white card or simply your hand in front of the detector, you can see yourself the pattern and evaluate it's length.
Below is a graph produced by a student after conducting their Fresnel experiment. And this is a graph presented in their submitted lab report.
There's actually numerous points here raising questions (e.g. what does "Value" measured in mV refer to?), but the most fascinating was how their diffracting pattern was measured at various distances (not specified what was the zero point) that stretched for a few... km long! In fact, their overall pattern appears to be around 4km. What a setup!!! I mean, LIGO's arm was 4km each. I do enjoy bragging about our
new teaching labs but this exceeds imagination.
Possible explanation: the lecturer understands that the x-axis values are in fact time (ms) that takes the detector to move across and the student labeled the axis without converting time values (automatically recorded by a software) into distance.
2. Electrons the size of The Sun
Another very favorite typo is below:
In this exercise, students had to estimate the electron rest mass. With a value of 1030 kg (!) we were shocked to (a) find out that electrons are bigger than our Sun (1.989 ×1030 kg) and (b) try and understand how did that fit in our lab by river Thames.
Possible explanation: the minus symbol is missing making it 10-30 kg (the actual value is 9.1×10-31 kg)
3. Tesla is an impractical unit
Last but not least, an example I chose to show every year to my 1st year students as "usual report mistakes and how to avoid". In below graph, the student is observing the Zeeman effect and the interference lines (Newton's rings) splitting caused by the presence of a magnetic field.
The student here claims they managed to measure in our lab magnetic fields as strong as those of sunspots. For reference, the Earth's magnetic field is in the range of 30 μΤ, the strength of a typical refrigerator magnet is 5 mT and strong magnetic fields in sunspots are of the order of 0.2 to 0.3 T.
Possible explanation: the student recorded their data in the lab without noting their units which in reality were mT.
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Take-home message: please be sympathetic to your lecturers, kindly asking you to always
check your units.
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