Determination of velocity of ultrasonic waves in liquids by debye-sears method
Answers
Subject matter of experiment
The experiment shows the diffraction of light on a permanent ultrasonic wave (DB-Sears effect) in a liquid. The sound velocity in the liquid (water) is stated by the dependency of the diffraction maximum on the wavelength of the dissimilar laser light and the frequency of the ultrasonic wave.
Theoretical and practical aspects of experimentation
In 1932, Debbie and Seiers showed that light experiences a diffraction while passing through the stimulated liquid for high frequency vibration. Ultrasound can be made more or less "visible" by using this effect. The density maxima and minima produced in liquid by a permanent or travel ultrasonic wave acts like a grating of optical diffraction here. The grating of such grating produced by an ultrasonic waveform matches the wavelength of this ultrasonic waveform constant. It can be determined through the diffraction pattern of light of a known wavelength laser beam. Since the wavelength is defined by frequency and sound velocity, the Debbie-Sears effect can be used in this experiment structure to determine the sound velocity in the fluid that is scanned with high accuracy sound (like water).
result
Figures show specific diffraction patterns for green and red laser light on a permanent ultrasonic wave in water on the sound frequencies from 3 and 4 3 MHz to 10 MHz (increase: 1 MHz). Since the ultrasonic frequency increases, the distance between different diffraction maxima increases even though the long wave red laser light expands more strongly. The number of diffraction commands is determined largely by the transmission characteristics of the sound check and frequency-dependent attenuation.