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pulse wave is a special waveform of
typically only one crest. Usually, they are associated
with sudden impacts or explosions. A pulse has a
velocity, amplitude, and wavelength.
Some questions about pulses you may have
are:
What is a pulse wave?
A pulse wave is a sudden distortion or
disturbance that travels through a material or medium.
It can be a distortion caused by a chain reaction car
accident on the freeway, people getting up suddenly in a
ball game, or the sudden compression of air caused by an
explosion.
In any material, the atoms or molecules
are usually evenly distributed. A short, sudden force
applied at one end of the material can set off a moving
chain reaction of disturbances to neighboring particles.
In other words, if a quick, sharp force
is applied to one end of an object, a group of its atoms
or molecules will move up to the next group and knock
them slightly forward. That group will then move forward
to the next group and move them slightly forward. This
continues until the disturbance or pulse travels through
the material.
Examples of pulse waves
Examples include sonic pulses, the wave
at a ballgame, and chain reaction accidents.
One example of the sudden compression
that causes a pulse is what happens when you hear and
feel an explosion. Thunder or a bursting balloon are
similar sonic pulses.
When an aircraft flies over at greater
than the speed of sound, it is followed by a double
exploding sound, called a sonic boom.
One example of this phenomenon is the
"wave" you often see going around the stadium at a ball
game. A group of fans suddenly stand up and sit down,
then one next to them do the same, and so on. From the
distance, an observer can see this disturbance move
around the ballpark or stadium.
Another example is type of chain
reaction accident that can happen when cars are stopped
on a busy freeway. It starts when a car rams into the
back of car stopped in traffic.
That car moves forward and hits the car
in front. That car then moves forward and hits the car
in front of it, and so on. An observer from above would
see the chain reaction of collisions move forward, while
the cars all seem to stay in approximately the same
location.
Difference from wave motion
Any pulse or moving distortion exhibits
velocity, amplitude and wavelength. Since it usually
only has one crest, a pulse does not have a frequency.
Some pulses may consist of a few crests, thus given them
a shortly-lived frequency.
The velocity is the speed at which the
distortion appears to travel. For example, in a chain
reaction collision on the freeway, the velocity is the
rate the collisions progress forward.
The amplitude of the distortion relates
to the intensity, compression, or height of the
disturbance. The amplitude of the "wave" at a ball game
would be the height the people are when they stand.
These two characteristics are important in explaining
wave motion.
The wavelength of a pulse can be defined
as the width of its crest.
A pulse is a special waveform of only
one or a few crests. Thunder and explosions are examples
of pulse waves. A pulse has a velocity, amplitude, and
wavelength. |
