<P> Longitudinal waves cause the medium to vibrate parallel to the direction of the wave . It consists of multiple compressions and rarefactions . The rarefaction is the farthest distance apart in the longitudinal wave and the compression is the closest distance together . The speed of the longitudinal wave is increased in higher index of refraction, due to the closer proximity of the atoms in the medium that is being compressed . Sound is considered a longitudinal wave . </P> <P> This type of wave travels along a surface that is between two media . An example of a surface wave would be waves in a pool, or in an ocean, lake, or any other type of water body . There are two types of surface waves, namely Rayleigh waves and Love waves . </P> <P> Rayleigh waves, also known as ground roll, are waves that travel as ripples with motion similar to those of waves on the surface of water . Rayleigh waves are much slower than body waves, roughly 90% of the velocity of body waves for a typical homogeneous elastic medium . </P> <P> A Love wave is a surface waves having horizontal waves that are shear or transverse to the direction of propagation . They usually travel slightly faster than Rayleigh waves, about 90% of the body wave velocity, and have the largest amplitude . </P>

What is a type of mechanical wave motion in an elastic medium