Understanding and Affecting Student Reasoning About Sound Waves

Student learning of sound waves can be helped through the creation of group-learning classroom materials whose development and design rely on explicit investigations into student understanding. We describe reasoning in terms of sets of resources, i.e. grouped building blocks of thinking that are commonly used in many different settings. Students in our university physics classes often used sets of resources that were different from the ones we wish them to use. By designing curriculum materials that ask students to think about the physics from a different view, we bring about improvement in student understanding of sound waves. Our curriculum modifications are specific to our own classes, but our description of student learning is more generally useful for teachers. We describe how students can use multiple sets of resources in their thinking, and raise questions that should be considered by both instructors and researchers.Comment: 23 pages, 4 figures, 3 tables, 28 references, 7 notes. Accepted for publication in the International Journal of Science Educatio

Microfabrication of Optically Flat Silicon Micro-Mirrors for Fully Programmable Micro-Diffraction Gratings

AbstractWe have fabricated and characterized a Fully Programmable Micro-Diffraction Grating (FPMDG) with 64 silicon micro-mirrors for spectral shaping in the visible and near-infrared wavelength range. The FPMDG arrays of 50μm and 80μm wide and 700μm long silicon micro-mirrors have been fabricated in a process based on anodic bonding of an 8μm-SOI wafer and a borosilicate glass wafer. The detrimental bending of the micro-mirrors during electrostatic actuation has been minimized through separation of the mechanical and optical sections of the device. Flexures incorporating serpentine structures have been used to reduce the actuation dependence on length and thickness. Independent addressing of the micro-mirrors with negligible cross-talk and with bending of the micro-mirrors smaller than 0.14μm over 700μm have been demonstrated

Optical characterization of fully programmable MEMS diffraction gratings

International audienceWe have fabricated and characterized fully programmable diffraction gratings consisting of 64 silicon micro-mirrors. The mirrors are 700 mu m long and 50 mu m wide with a fill factor of 90%. They are actuated electrostatically and move down by 1.25 mu m while showing negligible crosstalk and bowing as small as 0.14 mu m over 700 mu m. Extinction ratio up to 100 has been achieved by adjusting only 3 adjacent micro-mirrors. The gratings could operate either as light modulators up to 5 mu m or spectra generators up to 2.5 mu m. (C) 2012 Optical Society of Americ