WAVE MOTION AND SOUND(tranverse and longitudinal waves)
The general discussion of wave motion is important because the ideas of wave propagation are
ubiquitous. In nearly all areas of science (and therefore real life) energy is transferred via the vibrations
that make up waves. Examples of wave motion include waves on strings, water waves, seismic waves,,
sound, all electromagnetic radiation including light, heat, x-rays, etc. There are many common elements
to all the various types of wave motion that can be described - and these will be pointed out. There are
also some differences - especially between the mechanical waves such as waves on strings and sound
and all electromagnetic waves - which will be important in some discussions. What is common to all
forms of wave motion is the idea that a disturbance is being propagated from one place to another
without the necessity for the medium through which the disturbance is being propagated to itself be
transported. (We will see what that means shortly.)
It is useful to first classify wave motion into several different categories. Already mentioned are
mechanical waves and electromagnetic waves. This discussion will only deal with mechanical waves
(although many of the important ideas also apply to electromagnetic waves). Mechanical waves can be
either longitudinal or transverse. The distinction will be whether the disturbance that is being
propagated is in the direction of travel of the wave or perpendicular to it.
Longitudinal Waves: When a wave propagates through some medium, if the
local displacements of the medium that constitute the disturbance are in the
direction of travel of the disturbance, then the wave is longitudinal. An example
of a longitudinal wave is the pulse that can be sent along a stretched slinky by
shaking one end of the slinky along its length. The pulse moves along the line of
the slinky and ultimately makes the other end move. Notice that in this case, the individual coils of the
slinky vibrate back and forth about some equilibrium position, but there is no net movement of the
slinky itself. You can think of the slinky as the medium through which the pulse travels - and the wave
motion describes the disturbance rather than the slinky. Examples of longitudinal waves are sound
waves through the air or compression waves through some solid object.
Transverse Waves: A disturbance that is perpendicular to the direction of travel
are called transverse waves. Examples are waves on strings, surface waves on the
water, etc. That is, the wave itself travels along the string or water surface - but
displacements of the medium through which the wave travels are perpendicular to
the direction of the wave propagation.
by:Amelina Bte Ahsemat
