Sound INTENSITY decreases as you move away from the source because:
AThe sound waves slow down with distance
BAir absorbs all the energy quickly
CThe frequency of the sound changes
DThe sound energy spreads over a larger area (spherical surface) with increasing distance — so energy per unit area falls
Answer & Solution
Correct answer: D. The sound energy spreads over a larger area (spherical surface) with increasing distance — so energy per unit area falls
From a small point source, sound spreads as spherical waves. As radius r grows, the same total energy is distributed over a larger spherical surface area (4πr²). So the energy per unit area (intensity) falls roughly as 1/r². This is why a far-away speaker sounds faint even if its total output is loud.
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