Question

The intensity of sound from a point source is 1.0 × 10−6m−2 at a distance of 5.0 m from the source. What will be the intensity at a distance of 25 m from the source?

Solution

The correct option is A The power of the sound wave is intensity × surface area power =1 × 108 × 4π × 25 =100π 10−8 = 10−6π W Intensity at 25m =powersurfacearea =10−6π4π(25)2 =10−6625 × 4 =10−62500 =0.04 × 10−8 Wm−2

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