Question

What is the average value of the magnitude of the Poynting vector (intensity) at 1 meter from a 100-watt light bulb radiating in all directions

Answer 1

I = 7.96 W / m²

Step-by-step explanation:

The light bulb emits a power of P = 100W, this power is distributed over the surface of a sphere, thus the emission is in all directions.

Intensity is defined by power per unit area

I = P / A

The area of ​​a sphere is

A = 4π r²

we substitute

I = P / (4π r²)

in this case it tells us that the distance is r = 1 m

let's calculate

I = 100 / (4π 1²)

I = 7.96 W / m²