Question

A certain factory whistle can be heard up to a distance of 2.5 km. Assuming that the acoustic output of the whistle is uniform in all directions, how much acoustic power is emitted by the whistle? The threshold of human hearing is 1.0 × 10-12 W/m2.

Answer 1

Emitted power will be equal to
`7.85* 10^(-5)watt`

Step-by-step explanation:

It is given factory whistle can be heard up to a distance of R=2.5 km = 2500 m

Threshold of human hearing
`I=10^(-12)W/m^2`

We have to find the emitted power

Emitted power is equal to
`P=I* A`

`P=I* 4\pi R^2`

`P=10^(-12)* 4* 3.14* 2500^2=7.85* 10^(-5)watt`

So emitted power will be equal to
`7.85* 10^(-5)watt`