As the distance of a sound wave from its source quadruples, how is the intensity changed?

For sound spreading out from a source, intensity follows the inverse-square law: it is proportional to 1 divided by the square of the distance. If the distance quadruples, the intensity becomes 1 ÷ 4² = 1/16 of its original value. Therefore, it decreases by a factor of 16, choice B.

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