Energy Carried by Electromagnetic Waves Video Lessons

Concept

# Problem: A 60-W light bulb radiates electromagnetic waves uniformly in all directions. At a distance of 1.0 m from the bulb, the light intensity is I0, the average energy density of the waves is u0, and the rms electric and magnetic field values are E0 and B0, respectively.1. At 2.0 m from the bulb, what is the light intensity?2. At 2.0 m from the bulb, what is the rms magnetic field value?3. At 2.0 m from the bulb, what is the average energy density of the waves?

###### FREE Expert Solution

1. Light intensity:

$\overline{)\begin{array}{rcl}\frac{\mathbf{I}}{{\mathbf{I}}_{\mathbf{0}}}& {\mathbf{=}}& \frac{{{\mathbf{r}}_{\mathbf{0}}}^{\mathbf{2}}}{{\mathbf{r}}^{\mathbf{2}}}\\ {\mathbf{I}}& \mathbf{=}{\mathbf{I}}_{\mathbf{0}}& \mathbf{\left(}\frac{{{\mathbf{r}}_{\mathbf{0}}}^{\mathbf{2}}}{{\mathbf{r}}^{\mathbf{2}}}\mathbf{\right)}\end{array}}$

92% (42 ratings)
###### Problem Details

A 60-W light bulb radiates electromagnetic waves uniformly in all directions. At a distance of 1.0 m from the bulb, the light intensity is I0, the average energy density of the waves is u0, and the rms electric and magnetic field values are E0 and B0, respectively.

1. At 2.0 m from the bulb, what is the light intensity?

2. At 2.0 m from the bulb, what is the rms magnetic field value?

3. At 2.0 m from the bulb, what is the average energy density of the waves?