# At what distance from a 27 mW point source of electromagnetic waves is the electric field...

## Question:

At what distance from a {eq}27 \ mW {/eq} point source of electromagnetic waves is the electric field amplitude {eq}0.010 \ V / m {/eq}?

## Energy Density of Electromagnetic waves

The energy density of Electromagnetic wave is defined as the energy stored by the electric field component and magnetic field component of Electromagnetic wave.

Mathematically, {eq}U_{total}=\ U_{E}+\ U_{B}\\ U_{total}=\ \dfrac{\epsilon_{0} E_{0}^{2}}{2}+\ \dfrac{B_{0}^{2}}{2\mu_{0}} {/eq}