Analysis of thermal property of liquids by laser beam diffraction from surface acoustic wave

摘要

In order to analyzer the thermal properties of liquid, the diffracted laser beam (He-Ne Laser 633 nm 4.7 mW) pattern, from the acoustic waves generated by the vibration of diaphragm of loud speaker on the surface of liquid was observed. By changing the frequency of acoustic waves as 170 Hz, 220 Hz, and 300 Hz, the variation of diffraction pattern from the surface of distilled water, ethanol, and acetone were measured with decreasing the temperature from 50℃ to 20℃. The experimental result shows that as the temperature increases, the distance between the diffraction patterns also increases, and the surface tension was independent on the frequency of surface waves it depends only on the temperature. The obtained surface tensions at 20℃ are 7.21 × 10~(-2)N/m, 2.44 × 10~(-2) N/m, and 2.70 × 10~(-2) N/m for distilled water, ethanol, and acetone, respectively, and linearly decreased as the temperature increases. Also, they are independent to the frequency of surface wave.