Answer
Phone range increased by $\sqrt 5$ factor
Work Step by Step
Here we use the equation $I=\frac{P}{4\pi r^{2}}$ Where $I$ - wave intensity, P - power, r - distance from the source.
When P = 0.6 W,
$I=\frac{0.6}{4\pi r_{1}^{2}}W/m^{2}-(1)$
When P = 3 W,
$I=\frac{3}{4\pi r_{2}^{2}}W/m^{2}-(2)$
(1) = (2)
$\frac{0.6}{4\pi r_{1}^{2}}W/m^{2}=\frac{3}{4\pi r_{2}^{2}}W/m^{2}$
$r_{2}^{2}=5r_{1}^{2}=\gt r_{2}=\sqrt 5r_{1}$
Phone range increased by $\sqrt 5$ factor
