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The interference of waves is the phenomenon, which occurs when two waves meet while traveling along the same medium. The interference of waves causes the medium to take on a shape which results from the net effect of the two individual waves upon the particles of the medium. In case of sound wave, there are compressions and rarefactions. If two sound waves interfere at a given location in such a way that the compression of one wave meets up with the rarefaction of a second wave, destructive interference occurs. The net effect of the compression and rarefaction does not cause displacement of the particle. This is a form of destructive interference.
If the destructive interference continuously occurs then the corresponding locations are called nodes. Similarly, the positions where the constructive interference continuously occurs are called antinodes.
Standing Longitudinal Waves:
The standing longitudinal waves are the waves formed when two waves of same wave length, amplitude and frequency travel in opposite directions to each other and interfere. This can happen when a wave and its reflection interfere with each other. Consider the standing wave pattern in a string as in guitar:
This is not the only pattern seen in case of the vibration of guitar string. There are various patterns seen in case of the vibration of the guitar string:
It can be seen that each pattern has its own characteristics along with some basic characters:
a. There is an alternating pattern of nodes and antinodes.
b. There is either a half-number or whole number of waves within the established pattern on the string.
c. The nodal positions are established at the ends of the string where the string is clamped down in a fixed position.
d. One pattern is related to the next pattern by the addition (or subtraction) of one or more nodes (and antinodes).
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Waves and Optics