Ultrasonic waves, light from

If a two-step mechanism, as shown in Eqs. (12.7) and (12.8), occurs, each product will be produced independently by alternating irradiation of ultrasound and light. An alternating irradiation was performed for overall water splitting under argon atmosphere. Ultrasonic wave must be irradiatea first followed by photoirradiation. This oraei of irradiation was decided from tbe scheme of sonophotocatalysis of water, as shown in Eqs. (12.7) and (12.8). As shown in Fig. 12.12, H2 and 02 were evolved by sonolysis and photocatalysis, respectively Thus each gaseous product was collected independently. 

Laser interferometry employs the principle of optical interference to recover the sought acoustic information from the light reflected from, or scattered by, a surface under ultrasonic vibration. Its non-contact nature makes laser probing a preferred alternative to contact methods in studying surface waves, their diffraction and damping by intrinsically rough surfaces. 

At lower ultrasonic frequencies (0.5-10 MHz), Raman-Nath diffraction of laser light by plane acoustic waves was used to measure the decay of acoustic energy inside an aerogel specimen [57], This method relies on the density variations produced by the sound wave that create a phase pattern inside the specimen. The intensity of the first order of the diffracted light beams is proportional to the sound intensity at the intercept of light and sound beam. In a log plot of sound intensity versus distance from the transducer, the slope is a measure of the attenuation. 

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