Standing Wave Formation
A GIF Animation
The animation below depicts two waves moving through a medium in opposite
directions. The blue wave is moving to the right and the green wave is moving to
the left. As is the case in any situation in which two waves meet while moving
along the same medium, interference will occur. The blue wave and the green wave
will interfere to form a new wave pattern known as the resultant. The resultant
in the animation below is shown in black. The resultant is merely the result of
the two individual waves - the blue wave and the green wave - added together in
accordance with the principle of superposition.
The result of the interference of the two waves above is a new wave
pattern known as a standing wave pattern. Standing waves are produced whenever
two waves of identical frequency interfere with one another while traveling
opposite directions along the same medium. Standing wave patterns are
characterized by certain fixed points along the medium which undergo no
displacement. These points of no displacement are called nodes (nodes can
be remembered as points of no desplacement); the
nodal positions are labeled by an "N" in the animation above. The nodes are
always located at the same location along the medium, giving the entire pattern
an appearance of standing still (thus the name "standing waves"). A careful
inspection of the above animation will reveal that the nodes are the result of
the destructive interference of the two interfering waves. At all times and at
all nodal points, the blue wave and the green wave interfere to completely
destroy each other, thus producing a node.
Midway between every consecutive nodal point are points which undergo
maximum displacement. These points are called anti-nodes; the anti-nodal nodal
positions are labeled by an "AN" in the animation above. Anti-nodes are points
along the medium which oscillate between a large positive displacement
and a large negative displacement. A careful inspection of the above
animation will reveal that the anti-nodes are the result of the constructive
interference of the two interfering waves.
In conclusion, standing wave patterns are produced as the result of the
repeated interference of two waves of identical frequency while moving in
opposite directions along the same medium. All standing wave patterns consist of
nodes and anti-nodes. The nodes are points of no displacement caused by the
destructive interference of the two waves. The anti-nodes result from the
constructive interference of the two waves and thus undergo maximum dispacement
from the rest position.
For more information on physical descriptions of waves, visit The Physics
Classroom. Specific information is available there on the following
topics:
Other animations can be seen at the Multimedia
Physics Studios. Other useful resources regarding the physics of motion and
waves is available through the Glenbrook South
Physics Home Page.
This page was created by Tom
Henderson of Glenbrook
South High School.
Comments and suggestions can be sent by e-mail to
Tom
Henderson.
This page last updated on 8/11/98.