Question

The sound intensity is 0.008$W/m^2$ at a distance 110 m from an isotropic point source: The power of the Source is approximately :

• A. 250.5 watt
• B. 550 watt
• C. 810 watt
• D. 1215.8 watt

Answer 1

The correct option is D 1215.8 watt

As in this isotropic point source are that ones which radiate uniform intensity in all direction .

so as the $I=0.008W/m^2$ at a distance of $r=110m$

we know that $\frac{p}{A}=I$

so $p=IA$

now sound will be radiated in spherical symmetry so

$A=4\times \pi \times r^2$

so $A=4\times \pi \times {110}^2$

so $A=151,976m^2$

so $P=0.008\times 151976$

so $P=1215.80W$