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Exploring the laboratory landscape: Classic experiments

Posted by Melissa on April 6, 2009

As an experimentalist, I naturally think labs are a critically important part of the physics major. I still remember it was the lab for my electronics class that sealed the deal on my becoming a physics major. I enjoy teaching labs, and I appreciate that labs can be particularly beneficial for students who are hands-on learners. Despite all this, I rarely think as deeply about teaching and designing labs as I do about my classroom teaching and activities. I think this is partly because of the limits of equipment budgets and the time involved in developing new labs. Both of these factors make it difficult to completely revamp the laboratory portion of a course, and thus when I inherit a course, I often adopt the labs that have already been used, making modifications where needed. Recently I’ve spent more time reflecting on various aspects of curricular labs, and over the coming days I’m going to use this forum to think aloud on this topic.

In my mind, there are a number of issues that must be considered… the function of “classic” experiments, the place of computer simulations, the balance between canned labs and build-an-experiment labs, the appropriate level of guidance, the importance of lab notebooks, write-ups, and oral presentations, the role of curricular labs as preparation for undergraduate research experiences.

Of course, before addressing any of these questions, one must begin by asking what are the goals for any particular lab? I don’t consider the main purpose of labs to be simply verifying ideas presented in the classroom. Rather, I consider labs to be an opportunity for skill building (from experimental techniques to visual presentation of data), introducing or clarifying concepts, and giving students an appreciation of various aspects of the experimental process. Andrew Morrison, in his article in The Physics Teacher in December 2008, noted a disconnect between students and faculty about the purpose of labs. When he asked his introductory physics students whether they agreed or disagreed with the following statement, “The main purpose of the lab is to reinforce concepts covered in the lecture,” nearly all students agreed. Morrison advocates discussing goals for labs with students early on in a course so as to address the discrepancy.

Eric Ayers, of CSU Chico, gave a great talk at a session on advanced labs at the AAPT Winter Meeting this year. In his talk, he emphasized that when planning labs it’s much more important to ask “What skills do I wants students to learn?” than “What experiments do I want students to do?” I think this is true of labs at many levels, not just the advanced lab. This brings me to one of the topics I’ve been thinking about…

The function of “classic” experiments

In modern physics and advanced lab courses, the “classic” experiments often play a large role–the Millikan oil drop experiment, the Frank-Hertz experiment, the Rutherford scattering experiment, etc. In my mind, the historical role of an experiment or the notion that “all physics majors do this experiment” is never a sufficient reason for including a particular experiment in the curriculum, but many of these classic experiments do give students skills and experience with particular types of data collection and analysis that are useful. In addition, it is possible to combine the experimental skills with an appreciation for the historical perspective. For example, in our sophomore level modern physics course, we have students do the Millikan oil drop experiment. The most important factor in having students do this experiment is NOT to have students prove that the fundamental unit of charge is 1.6 x 10^-19 C. Rather it’s a good introduction to some ideas in analysis and interpretation of data. In particular, I like to link this lab with an assigned paper on the Millikan/Ehrenhaft controversy, and the questions surrounding Millikan’s contention that his published results represent all data collected for a 60 day period when his lab notebooks indicate there is data that he did not include. Having done the experiment and seeing the difficulty of tracking the oil drops, students must begin to consider critically questions about the quality of data collected, the role of record-keeping, the obligations in reporting results, etc. In this case, the historical nature of the experiment and the associated controversy serve to get students to think about the ethical implications of data collection and analysis.

Coming soon… computer simulations in the lab

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One Response to “Exploring the laboratory landscape: Classic experiments”

  1. rob said

    i remember doing physics labs where we covered ESR, hall effect, rutherford scattering, decay of silver isotopes, mossbauer effect etc.

    i found that i enjoyed the labs more when i had a better grasp on the underlying physics. i didn’t have to expend too much thought on the physics and could concentrate on the experiment itself. the hall effect and silver isotope decay were fun. the mossbauer and ESR were less so.

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