On Sat, 23 Aug 2008 00:18:25 -0400, Joseph Gwinn wrote:


No, it's really *the* inverse square law. All forms of radiation follow
this; the effect is geometric. Lasers focus their energy into a narrow
beam, but that beam nonetheless spreads.

Think of this example. Starlight is almost parallel when it reaches us,
yet it is incoherent and most certainly follows the inverse square law.

Joe Gwinn


Specifically it is the inverse square law as applied to a point source that is
1/tan (half the divergence angle) away.

This will be a very large distance for a well collimated beam, but will still
obey the inverse square law.

E&OE :-)
Mark Rand