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Sound with intensity larger than 120 dB ...

Sound with intensity larger than 120 dB appears painful to a person. A small speaker delivers 2.0 W of audio output. How close can the person get to the speaker without hurting his ears ?

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The correct Answer is:
C, D
If sound level =120 dB,
then `I=intensity =1W/m^2`
Let the closet distance be x.
`So, Intensity `=(2/(4pix^2))=1`
`rarr x^2(2/(4pi))`
`rarr x=40cm`
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HC VERMA-SOUND WAVES-All Questions
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