This is the first of two closely related articles (Paper I and Paper II) that together illustrate how research in physics education has helped guide the design of instruction that has proved effective in improving student understanding of atomic spectroscopy. Most of the more than 1000 students who participated in this four-year investigation were science majors enrolled in the introductory calculus-based physics course at the University of Washington (UW) in Seattle, WA, USA. The others included graduate and undergraduate teaching assistants at UW and physics majors in introductory and advanced physics courses at the University of Zagreb, Zagreb, Croatia. About half of the latter group were preservice high school physics teachers. This article (Paper I) describes how several serious conceptual and reasoning difficulties were identified among students as they tried to relate a discrete line spectrum to the energy levels of atoms in a light source. Paper II illustrates how findings from this research informed the development of a tutorial that led to significant improvement in student understanding of atomic emission spectra.
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Results from our investigation into student understanding of the conditions under which discrete spectra are formed and the role of the equipment used to observe spectra will be described in a later paper.
In this paper, the term functional understanding connotes the ability to interpret a concept or observation properly, distinguish related concepts from one another, and do the reasoning required to make the proper connections between the concepts and the phenomena to which they apply.
Some students had also done a laboratory experiment on spectroscopy in which they had observed the line spectrum from helium. Although this was a small fraction of the students, it seems that this experience did not improve performance on the questions asked in this study.
The UW Honors course consists of students enrolled in a university honors program. Students in this section are interested in taking a physics course that goes into greater depth than do the regular sections. They tend to be strong students with good preparation, although the percentage of physics majors is essentially the same as in the regular course sections.
The tutorial, Atomic spectra, is included in the Second Edition of Tutorials in Introductory Physics (see Ref. 4).
During a few of the interviews, a diffraction grating was inserted between the mask and the screen after the students had predicted what they would see with the prism.
Results from two other questions that were used to probe student understanding of the role of the optical instruments that are used to observe line spectra will be discussed in a separate paper.
No students raised the issue of selection rules that might prevent transitions between some of the levels. If they had, their answers would have been counted as correct.
In some cases, Questions 2 and 3 were presented in black and white. Therefore, students were told that the wavelength increases to the right. That information also appeared on versions printed in color in order to help students who might be color-blind.
Question 2 was also given as a clicker question at the UW to 70 students in a sophomore-level course on quantum mechanics. Only 55% answered correctly even after discussing the question with one another.
The research-based development of the tutorial, Atomic spectra, is also described in Ref. 1.
