The intensity S of an electromagnetic wave refers to the power per area the wave imparts if it is absorbed by a surface. The intensity is determined by the strength of the magnetic and electric fields
The equation is expressed as
`I=P_s/(4pir^2)`
where
`P_s` is the power of source
`4pir^2` is the surface area of the sphere
This equation, Intensity of Electromagnetic Radiation, references 1 page