it may be the case that this derivation is not required by your particular syllabus. However, understanding how equations are derived from first principles will give you a deeper understanding of physics. This indirectly will probably lead to a better result.
The Inverse Square Law
The inverse square law relates to the intensity(I) at a distance (x) from a source.
I energy per unit time per unit area( unit J s-1m-2 )
The intensity is inversely proportional to the square of the displacement.
Consider electromagnetic radiation emanating in all directions from a source. At a distance x from the source the energy is spread over a sphere of radius x and area 4Πx2 .
If E is the energy radiated from the source in all directions per second, then the intensity I is the total energy divided by the area it is spread over.
