I found this, seems like it might be similar not sure though:
https://www.quora.com/Does-the-inverse-square-law-apply-to-m...
https://www.quora.com/Does-the-inverse-square-law-apply-to-m...
> That is not the case with the telecom tower, or a flashlight, or a laser. In those cases, radiation is directed, not equal in every direction. The inverse square law still applies, but distance is calculated from an apparent source well behind the actual energy source.