Student recognition of interference and diffraction patterns: An eye-tracking study

Previous studies have demonstrated that students have difficulties in applying the wave model of light to explain single-slit diffraction and double-slit interference patterns. In this study, we investigated if students could recognize typical interference and diffraction patterns at all. Eye movements of high-school students were measured while they were identifying patterns produced by monochromatic light on a double slit, single slit, and diffraction grating, and by white light on a diffraction grating. Most students had difficulties with recognizing double-slit interference pattern and diffraction grating pattern of monochromatic light. Identification of the single-slit diffraction pattern was easier probably due to its distinguishable central maximum. The easiest task for students was recognizing the diffraction pattern of white light on an optical grating. Eye-tracking data suggested that even students who incorrectly answered this question were aware that the diffraction grating separates white light into colors. Additionally, eye tracking revealed that students who identified patterns correctly attended more the correct pattern than other options, thus corroborating previous findings. Overall, the results indicate that the recognition of interference and diffraction patterns is quite demanding for students, suggesting that more attention should be paid to observing and understanding basic wave optics phenomena.

Figure 1

Example of one participant’s scan path for questions Q3 and Q4. The centers of circles show positions of fixations (when the eyes remain relatively still) and the lines show saccades (rapid eye movements between fixations). The radii of circles are proportional to the duration of fixations. The four green patterns on the left were possible answers for questions Q1, Q2, and Q3, whereas four patterns on the right were possible answers for question Q4.

Figure 2

Dwell times for multiple-choice answers ($a$, $b$, $c$, and $d$) for each question (Q1, Q2, Q3, and Q4), evaluated separately for students who correctly and incorrectly answered the question. Rectangles show correct answers. One or two asterisks indicate significantly different pairwise comparisons at levels of $p<0.05$ or $p<0.01$, respectively.

Figure 3

Fixation durations for multiple-choice answers ($a$, $b$, $c$, and $d$) for each question (Q1, Q2, Q3, and Q4), evaluated separately for students who correctly and incorrectly answered the question. Rectangles show correct answers. One or two asterisks indicate significantly different pairwise comparisons at levels of $p<0.05$ or $p<0.01$, respectively.