Reported By: YAN Mingxing
Translated By: HU Yujia
Edited By: Jennifer Taylor
September 2013, the research paper Geometric Explanation of Conic-section Interference Fringes in a Michelson Interferometer, jointly written by FANG Guangyu, HUANG Li, XIN Li, ZHAO Haifa and HUO Lei from the Department of Physics, School of Science in HIT, was published in the SCI indexed journal American Journal of Physics. This geometrical interpretation is not only beneficial to students’ study, but also to the development of teaching.
The Michelson interferometer is one of the most common optical interferometers, which plays an important role in modern physics and measurement technology. It has been an important point in physics-based theory courses and experimental courses in universities of science and technology. In order to compensate for optical path differences in the interferometer arms, it needs to put a compensating board into one of the arms optical paths. In many students’ opinions, even some teachers’, it seems that it needs the compensate board only when a non-monochromatic light source (such as white light) interferes. This paper clarified these misunderstandings. It uses common sense in daily life to explain the various conics of interference fringes showing after removing the compensate board: When the light passes through the sloping glass, the light source seems to deviate from its actual position. Just like watching underwater stones by the river, the position of the visual deviates from the actual position. This deviation varies with different perspectives. As long as you can see the deviation, the shape of interference fringes can be predicted correctly, and the deviation can be calculated by school level geometry knowledge.
Associate Professor FANG said that, during answering questions for students that they noticed that the explanation of Michelson interferometer in textbooks was not detailed enough, which may mislead students. Previously, the explanation of conic-section interference fringes used numerical methods. That was too hard for students to understand and practice since it was not only complicated to calculate, but also hard to understand. After much discussion, they found this easy geometrical interpretation. It is easier for students to understand, giving them both more complete theory and easier calculation. By using this interpretation, the calculation process can be simplified very much more than the formal method by optical software.
The Deputy Director of the Physics Experiment Center, LIU Jianlong said that, the method of explaining a difficult physics question by easy geometrical interpretation, as the paper does, can be learned through analogy in teaching. They intended to add their research to textbooks, and give students more freedom in experimental studying in order to stimulate their innovation potential. He also pointed out that, recently HIT have been focused on investment in the Physics Experiment Center, in encouraging young teachers to do research, leading to these teachers publishing many research papers. They encourage more teachers to publish their papers in SCI journals, so that foreign researchers will understand more about our new thinking regarding physics study.
