Variation of radiation force values with differing gas content of propagating media.

The experiments discussed here involve investigations of variations in radiation force values for ultrasound incident on an inverted cone of a sensitive radiation pressure balance. The variations were observed to coincide with changes in the oxygen content of a constant volume of water between the transducer and the inverted cone balance pan (Fig. 1; Materials and Methods). The relationship between intensity per unit area of ultrasound entering unit volume of water (I0 and the intensity at the exit face (/2) is expressed by the equation 12 = l ~ e x p ( 1 0 -3~) where /~ represents the intensity absorption coefficient for water. The absorption of water increases when water is progressively aerated, compared to degassed water and can be accounted for by considering gas bubbles as inhomogeneities in