Question

Part B

Answer 1

Answer:

Sound waves in liquids and gases involve alternating compression and rarefaction of material along a line defining the direction of propagation of the wave. These waves are known as longitudinal waves, and of course exist only in a medium that can be compressed and rarefied. In solids, sound energy also produces longitudinal waves, but it can also produce transverse waves, in which compression and rarefaction occurs perpendicular to the direction of propagation. These two waves propagate at different speeds, a phenomenon that is most noticeable in earthquakes. The first wave gives notice that the quake is coming, the second one does the damage. The time between the two tells you how far away the epicenter is. In water there is another kind of wave, called a gravity wave, the kind you see at the beach. All of these wave require a medium. There is no sound in a vacuum.