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Have you ever noticed the vibrations on
a guitar string? Or seen how polarized sunglasses cut
glare? Or heard the throbbing variations of sound in an
airliner? These are examples of different waveforms.
Waveforms
Examples of transverse waves are those
you would see on a vibrating string such as a guitar
string, water waves, and electromagnetic
waves--including visible light.
The guitar string and water waves
vibrate in one direction and thus are called linear
waves. Electromagnetic waves vibrate in all directions.
A guitar string vibrates only in one
direction and is called a linear wave. The first example
of our demonstration shows this type of waveform. Click
here and then click on Linear wave.
A polarizing filter is a special
material that only allows waves vibrating in one
direction to pass through it and blocks off waves
vibrating in the other directions. It essentially
changes a waveform that is vibrating in all directions
to become a linear wave vibrating in only one direction.
An example of using polarization is the
special sunglasses people wear to cut the reflected
glare when driving a car or sailing in a boat.
One special characteristic of a
polarizing filter is that if may shift the phase of the
wave. This can be seen in the second demonstration.
Click here and then click on Linear wave with polarizer.
Some special filters will shift the
phase of all directions in an electromagnetic wave, such
that it appears to be circular. The demonstration shows
how the wave vibration constantly changes its
orientation. Click here and then click on Circular wave.
Since a polarizing filter only lets
light that is vibrating in one direction pass through,
its effect on a circular wave is similar to that on a
standard electromagnetic wave, as seen in the
demonstration. Click here and then click on Circular
wave with polarizer.
An electromagnetic wave consists of an
electrical wave and a magnetic wave that are
perpendicular to each other. For the sake of
convenience, the first two demonstrations of a linear
wave did not include the magnetic portion of the
waveform. In reality, a linear electromagnetic wave
appears as in the demonstration.
There are some situations--especially in
electronics--where a waveform is not sinusoidal.
Instead, it follow a Gaussian shape--which is the
bell-shape of a probability curve. The demonstration
show this. Click here and then click on Gaussian.
When two wavelengths that are only
slightly different are added together, the resulting
waveform is a beat. The inner frequency is the average
of the two, which the outer envelope defines the
frequency of the difference between the two.
Piano tuners use beats to tell if a
piano is slightly out of tune compared with a tuning
fork. The pulsating hum you often hear in an airliner is
caused by the engines vibrating at lightly different
frequencies. Of course, sound waves are compression
waves, but they may be illustrated as transverse waves,
as shown in the following demonstration.
Waveforms for transverse waves can be
linear, circular, and in all directions. They can be
polarized and can have such shapes as Gaussian and beats |
