Question

The power of a point source is $18.75mW$. Find the intensity (in $mW/m^2$ ) $2.5m$ away from the source.

Answer 1

Answer: 0.24

$I=\frac{P}{4\pi r^2}=\frac{18.75}{4\pi \times (2.5{)}^2}$
$=0.24mW/m^2$