An EM wave radiation outwards from a dipole antenna with $E_0$ as the amplitude of its electric field vector . The electric field $E_0$ which transports significant energy from the source falls off as

Question

$\begin{array}{1 1} \large\frac{1}{r^3} \\\large\frac{1}{r^2} \\ \large\frac{1}{8} \\ remains\;constant \end{array} $