Diffraction of Light by Two Ultrasonic Waves of the Same Frequency

The diffraction of light by two parallel ultrasonic waves of the same frequency is investigated. Measurements which were made with waves 180° out of phase with each other agreed with the predicted results. When the two waves were made nearly identical, the diffraction vanished almost completely. It is suggested that this might be applied as a method for the comparison of ultrasonic pressures, the measurement of absorption, and the investigation of finite amplitude distortion.