Is the pressure at which liquid and vapour can coexist in equilibrium; the rate of evaporation is equal to the rate of condensation. Vapour pressure increases with temperature. Vapour pressure is independent of the amount of liquid present.A liquid boils when its vapour pressure is equal to the atmospheric pressure, or other external pressure.

Is an ultrasonic transducer that uses the principle of piezoelectric effect. Piezoelectricity is the name for the phenomenon whereby electric dipoles are generated in certain anisotropic crystals when subjected to mechanical stress. This effect was discovered in 1880 by Jaques and Pierre Curie. The same materials exhibit the converse effect in that they suffer a dimensional change under the influence of an electric field.

Acoustic cavitation. In a non-flowing system the ambient pressure can be varied by sending sound waves through the liquid. The ultrasonic sound waves are made up of alternate compressions and rarefactions. During the rarefaction cycle (low pressure) a lot of microscopic bubbles will grow and during the compression cycle (high pressure) each bubbles undergoes a collapse or implosion. These implosions of the bubbles produce shock waves in the liquid. These shock waves produced during the ultrasonic cleaning will reach any solid surface that is in the ultrasonic tank liquid.

Because the energy required to form a cavitation bubble is proportional to both vapour pressure and surface tension. Cavitation is difficult when the vapour pressure of a liquid is low (for example in cold water)

Ultrasonics is the branch of science that deals with ultrasound. Ultrasound is the portion of the frequency spectrum that is too high to be detected by average human hear. The study and applications of these vibrations of material medium are called ultrasonics.

We may distinguish four different type of cavitation. Hydrodinamic cavitation, Acoustic cavitation, Optic cavitation, Particle cavitation.

Cavitation is the formation and activity of bubbles (or cavities) in a liquid.

The bubbles may contain gas or vapour or a mixture of both gas and vapour.