INFLUENCE OF DIFFRACTION ON LASER-GENERATED ACOUSTIC WAVES PROPAGATING IN LIQUIDS

The effect of diffraction on the geometry of initially plane acoustic transients propagating in liquids is studied. Theoretical considerations concern the transition from plane to spherical waves upon passing the border between near and far wave zone. Experiments with CO₂-laser-generated acoustic waves in absorbing liquids are discussed. The wavefront curvatures and lateral extensions at different propagating distances in n-heptane are analyzed by high-speed shadowgraphy and measurements with a piezoelectric transducer. Good agreement between theory and experiment is obtained.