Diffraction of Wide and Narrow Light Beams by Distorted Finite Amplitude Progressive Ultrasonic Waves

Abstract

Results of an investigation of the diffraction of light passing through an ultrasonic wave of finite amplitude are given. A method is developed and used to determine the second harmonic component of the distorted ultrasonic wave at various distances from the transducer, while maintaining a constant local fundamental component. A wide light beam (giving discrete diffraction orders) is used for these determinations. It is then shown that the observed continuous light distribution (using a narrow light beam) is in good agreement with the theoretically predicted distribution. The effects of third and higher harmonics are neglected. These determinations of second harmonic are compared with values obtained from diffraction effects observed after passing the second harmonic component through an acoustic filter plate. Measurements were made at 3.0 Mc in water with approximately 23 of an atmosphere local ultrasonic pressure amplitude. (This work was supported by the Office of Ordnance Research, U. S. Army.)