CSET Practice Test on Waves

Waves traveling through a solid medium can be either
transverse waves or longitudinal waves. Yet waves
traveling through the bulk of a fluid (such as a liquid or
a gas) are always longitudinal waves. Transverse waves
require a relatively rigid medium in order to transmit
their energy. As one particle begins to move it must be
able to exert a pull on its nearest neighbor. If the
medium is not rigid as is the case with fluids, the
particles will slide past each other. This sliding action
which is characteristic of liquids and gases prevents  one
particle from displacing its neighbor in a direction
perpendicular to the energy transport. It is for this
reason that only longitudinal waves are observed moving
through the  bulk of liquids such as our oceans.
Earthquakes are capable of producing both transverse and
longitudinal waves which travel through the solid
structures of the Earth. When seismologists  began to
study earthquake waves they noticed that only longitudinal
waves were capable of traveling through the core of the
Earth. For this reason, geologists believe that the
Earth's core consists of a liquid - most likely molten
iron.

Speed = wavelength x frequency 90 m/sec = 2.5 meters  x
frequency 90  /  2.5 = 36 Hz