Understand First Order Principles of Energy Dispersion

[jlenard]

Inverse square law

Does anyone have an absolute basic understanding of "first order principles of energy dispersion"

(A) Energy from a point source
disperses spherically at the inverse square law.
(B) Energy from an infinite line source
disperses cylindrically at ½ inverse square law.

Question?
What is the energy dispersion from a finite line source?

Measured 90deg from center of line source, at distance x, where transition from ½ inverse square law, back to inverse square law, takes place.

Can anyone throw light on this question without diversions?
1 First order principles only.
2 In space, zero boundaries.
3 Line length magnitudes greater than any wavelength of energy dispersed.

Thank you.

 

[lippyka]

Answer: The energy dispersion from a finite line source is the same as from an infinite line source, i.e., cylindrically at ½ inverse square law. However, the transition from ½ inverse square law to inverse square law will take place when the distance from the line source (x) is equal to or greater than the length of the finite line source.