How many metres further would the sound intensity be 1/2 times as much as that at a distance of 3 m from an acoustic source?

Solution :

Let, intensity at distance 3 m from the acoustic source is .

We need to find the distance d where the intensity is .

Now, we know intensity is inversely proportional to square of distance between the source.

Therefore, intensity will be halved at a distance of .

the awnser is group 12