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Pulse Waves
by Ron Kurtus (revised 27 March 2009)
A pulse wave is a special waveform that typically has one major crest, along with several minor crests. The ideal pulse would have only one crest, but that is not possible in many cases.
. It is often associated with a sudden impact or explosion and is also called a shock wave.
A single water wave from a splash, a sonic boom from an aircraft breaking the sound barrier and an electromagnetic pulse from a nuclear explosion are examples of pulse waves.
As with other waveforms, a pulse has a velocity and amplitude. Since there is only one crest, there is no frequency or true wavelength, although the width of the pulse relates to wavelength.
Questions you may have include:
- What is a pulse?
- What are some examples of pulses?
- How is a pulse different than a regular wave?
This lesson will answer those questions. There is a mini-quiz near the end of the lesson.
Useful tools: Metric-English Conversion | Scientific Calculator.
Water
Bullet creates a shock wave in air
Wave packet
Water drop creates wave packet
Slinky
Sound
The sound created by any impact or explosion can be a pulse wave if the duration is short enough.
Electromagnetic
Electricity
Electrical surge in power
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.
Sudden distortion with atoms
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 ball game, and chain reaction accidents.
Pulse wave in water
Explosion
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.
Sonic boom
When an aircraft flies over at greater than the speed of sound, it is followed by a double exploding sound, called a sonic boom.
The wave
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.
Chain reaction accident
Another example is the 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 another car that is stopped in traffic.
That car then moves forward and hits the car in front of it. The third 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.
Pulse velocity
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.
Pulse amplitude
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.
Wavelength
The wavelength of a pulse can be defined as approximately the width of its base.
Summary
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.
Create a sonic boom with your knowledge
Resources
The following resources provide information on this subject:
Websites
Books
Top-rated
books on Wave Motion
Mini-quiz to check your understanding
If you got all three correct, you are on your way to becoming a Champion in Physics. If you had problems, you had better look over the material again.
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Pulse Waves