Answer #48

The correct answer is B: Excessive energy can cause formation of gas bubbles in the medium. There are two major forms of bioeffects: thermal and mechanical (Choice A is not correct). Thermal effects relate to increased temperature in a medium from the interaction of a sound wave with the medium. This temperature increase is usually on the order of several degrees Celsius. High temperatures can be bad for the local cells and tissues.

Mechanical bioeffects include cavitation, where excess energy can cause small gas bubble formation in the medium (Choice B). Cavitation occurs usually during the sound wave's peak rarefactional pressure and not during compression (Choice C is not correct). The bubbles can be either stable or transient (Choice E is not correct). In transient cavitation there is formation and then collapse and implosion of the bubble with localized temperatures that can be very high (up to 10,000 Kelvin!) (Choice D is not correct). Stable cavitation causes bubbles which can be long lived.