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Explore the superposition principle, standing waves, and beats phenomenon in wave theory. Learn how different wave disturbances interact independently, resulting in varying amplitudes over time in a medium. Discover how frequency differences create beats and their impact. Practice calculating average frequencies for comprehensive understanding.
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We have already discussed interference of transverse waves in strings and of water waves in the ripple tank. • There is abundant experimental evidence that two or more wave disturbances can travel through the same medium independently of one another.
The superposition principle shows us that the displacement of a particle of a medium at any time is the vector sum of the displacements it would experience from the individual waves acting alone. A standing wave is formed by two wave trains of the same frequency and amplitude traveling through a medium in opposite directions.
Two wave trains of slightly different frequencies traveling in the same direction through a medium will interfere in a different way. At any fixed point in the medium through which the waves pass, their superposition gives a wave characterized by an amplitude that varies with time.
In curve (A) the frequency is 8 hz, and in (B) it is 10 hz. Curve (C) shows the combined effect of these two waves at a fixed point in their pathway. This resultant wave varies periodically in amplitude with time. Such amplitude pulsations are called beats. • The average human ear can distinguish beats up to a frequency of approximately ten per second.
The number of beats per second equals the difference between the frequencies of the component waves. • To find the average frequency: fav = 1/2(fl + fh)