Debye-Sears 효과의 특성과 과학교수학습에의 적용

Abstract

In 1932 Debye and Sears showed for the first time that light crossing a liquid medium that is disturbed by a high frequency ultrasound undergoes a diffraction. The density maxima and minima of the medium in a standing or continuously progressing wave act like lattice elements of an optical diffraction lattice. The lattice constant corresponds to the wavelength of the ultrasound and therefore depends on their frequency and sound velocity of the medium. The diffraction phenomenon is called as Debye and Sears effect and it includes the Raman-Nath diffraction and the Bragg diffraction. The Raman-Nath diffraction is occurred when the light beam with the wider width than the wave length of the light incidents the medium. From the diffraction images of the light beam by the Raman-Nath diffraction, the wavelength of the sound wave can be determined, and that the sound velocity in the medium can be calculated. In this study sound speed was measured in change of the temperature of the water between 10∼50 ℃, and in several liquids such as ethanol, methanol, and distilled water were measured at 15 ℃ temperature by using the Raman-Nath diffraction patterns of the Debye-Sears effect. The obtained sound speeds were compared with the values from literatures. It is noted that the values are in good agreement. In addition, the contents related to acoustics or wave physics in the curriculum for middle school students were searched in this study. As the results, it is noted that the experimental method and the obtained results in this study are valuable for the Wave Physics Instruction and Learning for middle or high school students.