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A point source broadcasts sound into a uniform medium. If the distance from the source is tripled how does the intensity change?

Correct answer: A. It becomes one-ninth as large

  • A. It becomes one-ninth as large
  • B. It becomes one-third as large
  • C. It becomes three times larger
  • D. It becomes nine times large

Explanation

Intensity is inversely proportional to the square(due to the inverse square law) of distance from the source, as a larger distance means the wave is more spread out hence less energy per unit area.

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About Waves

Progressive waves transfer energy through oscillations, with wavelength, frequency, amplitude and wave speed related by v = fλ; sound speed depends on the medium. Superposition produces interference and stationary waves in strings and organ pipes, while simple harmonic motion describes the oscillation itself and must be distinguished from wave propagation.

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