Hello PF! I've got a strange question for you physics boffins; assuming for a moment that lasers obeyed the inverse square law, what range would a typical 1mW red laser have in the atmosphere?
Actually, it not the "isotropic" bit that counts. It's whether or not they behave as a point source in the same location that counts. A directional radio antenna with a phase centre at its physical centre or even a lamp in a black sphere with a hole in it will produce a flux that follows the inverse square law - in their main beam.Welcome to PF,
Only things that emit isotropically (i.e. the same in all directions) obey the inverse square law. Also, it's unclear what you mean by "what range" would the laser have? Do you mean how far away could you be from the source of the laser and still detect emission from it? You'd have to specify what the sensitivity limit of your detector was, and it would also depend on what the background noise level was.
Depends on the laser design and the eye.At approximately what distance would the laser not be detectable if shone directly into the observer's eye.
Thanks for your reply mfb. So if (hypothetically) the "brightness" (somehow) fell off with the square of the distance of the observer from the source, what would that reduce the range to?~1000 photons/s seems realistic
1mW of ~700nm corresponds to ~4*10^15 photons/s.
It does so for large distances, and I already took this into account with the assumption that the spread is ~1cm over 10m distance.So if (hypothetically) the "brightness" (somehow) fell off with the square of the distance of the observer from the source