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Question

Physics Question on Waves

If the amplitude of sound is doubled and the frequency reduced to one fourth, the intensity of sound at the same point will be

A

increasing by a factor of 2

B

decreasing by a factor of 2

C

decreasing by a factor of 1/4

D

unchanged

Answer

decreasing by a factor of 1/4

Explanation

Solution

Intensity ?(amplitude)2? (amplitude)^2 and also intensity
?(frequency)2? (frequency)^2. Therefore
original I?A2ω2I ? A^2 \omega^2
I?4A2ω216i.e.,14II' ? 4 A^2\frac{\omega^2}{16} i.e., \frac{1}{4}I